[QUOTE=andytiedye;15996120]Analog signals are MUCH easier to receive than digital signals,
especially if the there are hills and/or trees.

I can tell you've never been to the Texas Panhandle :D No hills not a lot of trees. Think rolling plains (with very little roll).

Back to topic. I can get all of the UHF stations with no problems and all the transmitters are close together. The VHF stations are the ones I am having trouble getting. I was thinking there must be something wrong with our installation or amp or something.

Gosh, we must not be looking at the same thing. Here is the link listed on th tvfool page


If you would like to share these results with others, this page can be referenced as:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3de288f9b2df


OK, that makes more sense. You definitely need a rotator for the PBS channel. Also, not to sound like a broken record here:), but use an HLSJ between the hi vhf antenna and the preamp vhf input to further pre-filter the signal. Make sure the FM trap is "in" on the 7777 as well (although it may not matter that much with the HLSJ in-line).

Edit: sorry, didn't see that you have two PBS digital 8 nearly 180 degrees apart. This may give you problems with co-channel interference. Assuming you only need the one at 50 miles out, you shouldn't need a rotator.

Boy, I sure got different results than you did for that zip code...mine came up just as cpcat's did.

With the link you provided, that looks WORSE. You have 2 post transition channel 8s nearly 180 degrees apart and nearly the same strength. I would be willing to bet that there is enough interference to make both channels unuseable.

Your UHF stations are easy...you only have real channel 15 and 19 with KCIT and KAMR, and they are both at 247 degrees magnetic.

As I said, you have a pair of physical channel 8s. They are 171 degrees apart. The YA-1713 is not terribly directional, and will pick up the unwanted channel from the backside just enough to block the wanted channel. Can you put your antennas on the west southwest side of your house with the VHF antenna well below the roofline? This may block enough of the rear signal to allow reliable reception of your wanted KACV. Point the 1713 at 248 degrees magnetic and see what happens.

Bill

My Sunkey's, APEX DT502's, and Zinwell ZAT-970A all have Strength and Quality meters.

I'd like to see an 8-VSB meter that is closer to 15£, then $200 U.S.

Anyone come across an very inexpensive USB tuner/software (OpenSource would be best) setup to turn my laptop into a Spectrum Analyzer?

I'm new so if this is the wrong spot to post this let me hear it. I'm wondering if some one could recommend a setup for me. I currently have D** HR20 with a Winegard GS2000 Amplified on roof and a 2002 53" HD ready Hitachi. I'll try and link my tvfool stats. But in case it doesnt work I am in area code 71373 Vidalia, La. and maybe ya'll could run it and recommend something. I get 3 stations of knoe 8 57.3 miles, kard 36-14.1 56.8 miles. I would really like to get kalb 35 5.1 89.4 miles, wbrz 13 2.1 80 miles, wafb 46 9.1 79.6 miles, and the one strange to me wntz 49 48.1 at only 16 miles. I know they are scattered so if a rotar is needed please say so. Thanks a million. Oh yeah flat land. http://www.tvfool.com/modeling/?id=84ff608e91

I
currently have a NTSC channel 6 and a strong 88.3 FM. One 88-108
trap helps, but using 2 of them does a real number on channel 6.
If channel 6 was staying around I'd look into a better antenna
and higher quality filters.

Your situation is even tighter than mine right now, heh. But at least your channel 6 is going away. My digital channel 6 will be on real channel 6 after the transistion. Yeah, I may adjust the trap soon. Its kind of a toss up whether judging the analog picture or reading the slow moving CECB signal meters would be better to adjust to.
I do have an upgraded CM1221 vee boom vhf antenna for channels 6 and 12, so I should be good no matter what, heh.

Why not peak reception now, while you have the analog station, and then repeak after it goes digital.

I know they are scattered so if a rotar is needed please say so.

This is what I'd do, but I'm not fond of rotators. I channel surf too much.

A High band VHF only for channels 8 and 11 aimed at 319 degrees.

Antennacraft Y10-7-13 is one option.

A wide beam UHF only for 26 and 49. Aim it at 270 degrees. Fox at 294 will be close enough.

Channel Master 4221 is a good choice.

A UHF only for channel 35 aimed at 235 degrees.

Another 4221 would be fine.

Connect the two UHF antennas together with a Channel Master Jointenna tuned to channel 35. Alternately, you can use the ganging tricks shown here: http://www.hdtvprimer.com/ANTENNAS/ganging.html The first is simpler, the second is cheaper. Add the UHF signals to the VHF antenna with a Pico Macom UVSJ. That's 5 networks without a rotor.

WAFB and WBRZ are too weak unless you want to erect a tall tower. That's where I'd put a rotor to pick up anything you can't get with the first antenna. Use an A/B switch to watch anything unusual.

> But at least your channel 6 is going away. My digital channel 6
> will be on real channel 6 after the transistion. Yeah, I may
> adjust the trap soon. Its kind of a toss up whether judging
> the analog picture or reading the slow moving CECB signal
> meters would be better to adjust to.

A spectrum analyzer would be very useful for this, but they are
expensive.

Playing with FM traps with NTSC may provide insight into what
the filters do to the signal. An ATSC tuner will react
somewhat differently to a filter's intrusion, so the optimum
filtering might be a bit different.

With ATSC, what ultimately matters is getting the signal good
enough so that all the packets are ok after applying forward
error correction (FEC), plus some margin for varying conditions.
Some tuners will tell you this. If FEC is successful, you have
a perfect copy of the bits transmitted by the TV station. This
is useful to know, because then you know that any remaining
glitches are the fault of the TV station. And yes, some TV
stations transmit bogus data streams. Sometimes bogus enough
to crash the mpeg decoder.

HDTV Primer has a new page about the 4228HD (and the new DB8).

http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

The bad news is that the new 4228HD and DB-8 are both wrecks. The good news is that the 4228HD can easily be turned into the best UHF antenna presently available.

I also noticed a gain chart for the Clearstream 2. It does not break 10dBi, which seems in line with the AD specs. Still, it is not a match for 4-bay bow-tie class antenna.

From that web page about the DB8's...
All the 8-bay makers seem to be copying each other’s mistakes.

Is there a good chance Channel Master and Antennas Direct aren't even making these antenna, and they are just slapping their name on some import? CM, AD, Terrestrial Digital and Aspen Eagle stuff all looks identical.

I am trying to help my niece in Jefferson, Ga. receive the Atlanta dt stations. Antenna web says no chance... but tv fool gives them a good chance. We have done pretty well on analog, but recently decided to go digital. Can not receive ch 2, digital 39. Their antenna set up is, the vhf section of cm 3020 (uhf section removed), mounted about four feet higher is a cm 4228. The lead from the vhf section is combined with the 4228 on that antenna's connection point, per instructons.
Would this combination cause dt 39 to be weak, would we better off removing the vhf section. Dt 8 (gptv) will be a must (tv fool says their strongest signal) and I am thinking the 4228 should be able pull in the ch 8 signal. Location 34 07 51 56N, 83 35 44
99W. thanks for any help...

Preliminary Clearstream2 info (see also C2) can be found here:
http://www.hdtvprimer.com/ANTENNAS/
Note that C2 html links don't work right....

And yes, some TV stations transmit bogus data streams. Sometimes bogus enough to crash the mpeg decoder.
Any purpose as to why they do this ?

I am in the process of trying to determine whether my parents will be able to even recieve digital signals intheir location. It appears that they are in a poor area distance-wise to any of the stations they have recieved over analog. I am wondering whether it is feasible to even try to set up a antenna system for them or not. I hope I got the location as close as I remember. http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d6663b3f005

I am in the process of trying to determine whether my parents will be able to even receive digital signals in their location.

It'll work. ABC will be the hardest to receive.

Aim a big Winegard 7-69 antenna at 37 degrees. Use a Winegard PR-8800 for 281 degrees. Put it above the first antenna. Get a Jointenna for channel 20. Use a preamp.

I am trying to help my niece in Jefferson, Ga. receive the Atlanta dt stations.

Assuming that your data is correct, channel 39 can be received with a 4228. It may be aimed wrong to find a compromise direction for WNEG. It's also possible that the method of combining the 3020 is causing a problem. The only way that you'll know is to try it.

Yet, if she don't yet have a preamp, that may fix channel 39 without any antenna modifications.

Channels 8 & 10 should be strong enough for a 4228.

To get WNEG you'd need a second UHF only antenna and a Jointenna for channel 25, but that will ruin reception of MyNET on channel 24.

It'll work. ABC will be the hardest to receive.

Aim a big Winegard 7-69 antenna at 37 degrees. Use a Winegard PR-8800 for 281 degrees. Put it above the first antenna. Get a Jointenna for channel 20. Use a preamp. Thanks for the reply. I was wondering if a 91 XG aimed at 34 degrees would be suitable as all of those stations are together. The reason is since they are elderly and money is a problem for them but I could swing a 91 for them since I went and got myself aWinegard 7698 put up several days ago but they are not cheap. So do you think the 91 would work? thanks.

I also noticed a gain chart for the Clearstream 2. It does not break 10dBi, which seems in line with the AD specs. Still, it is not a match for 4-bay bow-tie class antenna.

Yeah. But one of the advantages of that design is that it exhibits a very wide beam pattern for its gain compared to other 10dbi antennas.

Even with the meters included with ATSC devices, it's still a two man job. With a fast response hand-held meter, one person could do the job a lot easier. Spectrum analyzers would be the best, by a long shot.

Poor man version.

Get a USB ATSC tuner, plug it into a LT and now you have a battery powered HD monitor and signal meter.

I used this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16815116031

USB ATSC tuner run about $50-$70. It is nothing like a spectrum analyzer but it worked for me to help align my mother's antenna better.

If the Laptop doesn't have a 2Ghz processor it won't be able to decode in realtime making analysis more difficult (pauses, freezing, glitches are caused by the CPU falling behind the mpeg stream not the reception). The signal meter still works though.

So do you think the 91 would work?

Nope. The 91XG won't receive WHO on channel 13.

Nope. The 91XG won't receive WHO on channel 13. Thanks for the advice. I will look into another antenna option like my Winegard 7698 or 97 for them. I also found this meter just for my own basic use to help in my antenna alignment so will this be adequate? http://www.antennasdirect.com/sm100.html

I have a question regarding the use of a solid screen wire reflector used with the Gray Hoverman design of antenna. Does the screen need to stay insulated away from the mast attachments? I know on the CM4221 that the screen is grounded to the mast. I realize in order for the co-linear reflector or split screen reflector to work it needs to be insulated from the mast or the effects will be altered.

Ed Boggs

There is a Channel Master 4251 7 ft Parabolic UHF antenna for sale on ebay, new in box, local pickup Peoria Illinois....if anyone is interested. Not mine.

I have a question regarding the use of a solid screen wire reflector used with the Gray Hoverman design of antenna. Does the screen need to stay insulated away from the mast attachments? I know on the CM4221 that the screen is grounded to the mast. I realize in order for the co-linear reflector or split screen reflector to work it needs to be insulated from the mast or the effects will be altered.

Ed Boggs

Yep, the screen needs to stay insulated away from the mast attachments for the split screen reflector. Otherwise you short the two sections together for .5 to 1 dbi less gain, like you do using a solid screen wire reflector. Splitting the solid screen into two sections is very easy once the antenna is completed.

Yeah. But one of the advantages of that design is that it exhibits a very wide beam pattern for its gain compared to other 10dbi antennas.

I wonder how the ClearSteam4 stacks up against the newer 4228HD and DB-8 8-bay models.

That meter seems to be a full band device that measures RF 14 to 51. It can also be had here;

http://www.htmart.com/product.php?productid=775&cat=53&page=1

Issue with UHF DTV signal that is only 5.5 miles away:

I've just installed a Channel Master CM-3016 in the attic of a 1 story home without a ground. Most homes in the area are 1 story but a lot of trees are in the direction of towers (trying to get away without having to install it outside). According to AntennaWeb the stations I care about are all within 20 degrees of each other are no more than 10 miles away and are all yellow or red.

I currently have the antenna pointing at 217 degrees and it is sitting on the rafters as I haven't been able to install mast yet. I've installed a preamp Channel Master Spartan 3 CM-0068 and currently running directly to TV with no splits to test (I plan on splitting 4-way with an 8Db amplified splitter). The RG-6 Quad run from the Antenna to preamp power plug is about 10 feet long.

The preamp didn't have any wire supplied to connect to antenna so I used all I had available, which was individually sheathed 10-gauge stranded (as in they are not run together in the same sheath). This is currently about 18" long. It'll be shortned to probably about 8" once it is installed on mast. Is this a possible issue? What should I use?

Every channel is working except PeachTree TV (TBS replacement). The analog tower (uhf yellow) @ 8.8 miles 227 degrees comes in pretty clear (you can see very faint ghost image). The digital tower (uhf yellow) @ 5.5 miles 217 degrees won't come in.

I have a signal meter on my Samsung LCD which goes to a total of 12 bars. Most DTV channels are between 7-9 bars with NBC being only 5-6 (NBC is red VHF @ 8 miles 202 degrees). I haven't been able to test NBC during the day, but right now at 9 PM I'm having no issues.

The peachtree DTV signal meter will drop in and out, reaching up to 8 bars, but the constant drop out of signal causes the picture to rarely appear.

My next step is to install the mast and have my wife at the TV while I'm in the attic changing the direction to see if that makes an improvement.

I'm posting to see if you may see any flaw in my install that is causing this weak DTV channel or if it is just an attic problem and I'll probably have to install it outside to resolve the issue.

Have you tried it without the preamp? Most people would say you're too close to use a preamp, in fact it can actually be counterproductive because too strong a signal can easily overload your tuner or even the preamp itself.

That meter seems to be a full band device that measures RF 14 to 51. It can also be had here;

http://www.htmart.com/product.php?productid=775&cat=53&page=1 Thanks for the headsup on that product and website.

Have you tried it without the preamp? Most people would say you're too close to use a preamp, in fact it can actually be counterproductive because too strong a signal can easily overload your tuner or even the preamp itself.

I originally ran it without the preamp and peachtree would work almost all the time. However, NBC and ABC would drop out or not appear. Now those two work and peachtree is problematic.

But I'll keep it in mind that it may work better without the preamp. Wasn't aware of that.

Also snag a length of 300ohm twin lead to do a proper connection between the preamp and antenna.

Can't hurt.

jtm

Also snag a length of 300ohm twin lead to do a proper connection between the preamp and antenna.

Can't hurt.

jtm


300 Ohm like this? (http://shop2.frys.com/product/5231747?site=sr:SEARCH:MAIN_RSLT_PG)

The wire was so thin I wasn't sure it was good enough and it was breaking apart when I tried to tighten it to the antenna (I cut apart a 300-ohm twin lead radio antenna I had). This compared to the 300 to 75 balun that came with the antenna, which is solid, probably 18 or 16 awg.

Is that wire linked good and I should just use some crimps to attach it to the preamp and antenna? I've tried calling around to TV/electronic stores most of which don't even answer and one that even said, "300 ohm isn't used anymore - get 75 ohm instead." I couldn't explain to him what I was trying to do for the life of me :)

Do you know of a good place I could buy some online?


Also, to test the signal 'without the preamp' do you think I could do this by taking the coax currently going into the preamp power unit and connecting it directly to the TV?

Your preamp should be mounted pretty close to the antenna on the mast. How long is the 300ohm run?

The 300ohm line should be at least 3 widths away from any metal in its run to maintain the proper impedence.

I get my wire from www.thewireman.com for my ham antennas but I doubt you'd want as much as their minimum order.

What sort of screw downs are causing you to break the wire? Perhaps you should put the wire under a flatwasher to prevent breaking it.

jtm

Thanks for the advice. I will look into another antenna option like my Winegard 7698 or 97 for them. I also found this meter just for my own basic use to help in my antenna alignment so will this be adequate? http://www.antennasdirect.com/sm100.html

That meter has no way to know which channel you want to aim at.

The preamp is currently sitting on the attic insulation as is the antenna since I need to install a 2x4 across my trust in order to install the mast at the right place. Also, I wasn't sure of where to find a 'mast' and I bought a 2 foot fan metal extention pole, not painted. Does that matter?

The 300-ohm run I was trying to install was about 16 inches, which I would have shortened to as short as possible once mounted on mast, while leaving a slight dip in the wire.

I noticed the 300-ohm from the website you mentioned is 18 awg. That's around what I was thinking it should be. All I've been able to find locally is probably 24 awg or smaller.

I wonder how the ClearSteam4 stacks up against the newer 4228HD and DB-8 8-bay models.
When you stack two identical antennas together and do it right, you should expect about 2.5 dbi increase in gain (3 dbi is theoretical). AFAIK, AD is changing their marketing literature to show about 12.5 dbi gain on the CS4. The 4228HD as shipped, is worse than the old 4228, per Ken Nist. I havent looked at the DB-8, I rather look at mclapps 8 bay, heh.

I've installed a preamp Channel Master Spartan 3 CM-0068 and currently running directly to TV with no splits to test (I plan on splitting 4-way with an 8Db amplified splitter). The RG-6 Quad run from the Antenna to preamp power plug is about 10 feet long.

Try installing a non-powered 4-way. Be sure to terminate the other three ports.

The preamp didn't have any wire supplied to connect to antenna so I used all I had available, which was individually sheathed 10-gauge stranded (as in they are not run together in the same sheath). This is currently about 18" long. It'll be shortned to probably about 8" once it is installed on mast. Is this a possible issue? What should I use?
I'd talk to a local installation company/repair shop and see if you can't get a foot or two of high quality 300 Ohm cable.

I noticed the 300-ohm from the website you mentioned is 18 awg. That's around what I was thinking it should be. All I've been able to find locally is probably 24 awg or smaller.
Except for open wire, 18 gauge is rare for 300ohm wire. 20 and 22 gauge (and for indoor use, 24 gauge) were the most common for twin lead.

Location is very important. I have read many times on this board that even moving an antenna six inches can make a big difference. Tonight, I discovered one of thos differences. I lowered the mounting spot of my Eagle Aspen DB2 down 12 inches from its previous spot, and picked up two additional digital channels (45.1, 45.2).

This got me thinking!

Tomorrow night, I am going to mount a pole to my TV stand and put the DB2 above the TV. This will give the antenna a naked view of the window behind it, and in front of it, that it does not have now.

So, the current channel count is 11 analog, 23 digital. I have a 29db amplifier on order. I am curious if I will suddenly find 7.1 and 9.1 with it.

Except for open wire, 18 gauge is rare for 300ohm wire. 20 and 22 gauge (and for indoor use, 24 gauge) were the most common for twin lead.

So you think the really thin wire from fry's is acceptable and use it with crimps for a better connection?

Try installing a non-powered 4-way. Be sure to terminate the other three ports.


I'll buy some terminators (http://shop4.frys.com/product/1525076;jsessionid=Oe91rgTxmhGjjmdGPpw9cQ**.node3?site=sr:SE ARCH:MAIN_RSLT_PG)and try this. Didn't know open points needed to be terminated (makes sense, though!) and I'll only be using 3 of them so good to know.

That meter has no way to know which channel you want to aim at. The channels I will aim at are all around 300 t0 333 so this should help. I have a lot of trees in the way so at leaf out I may be able to re-orient the antenna as needed. The 7698 has improved my reception by 25 to 30% just by looking at my tv meter but I thought this may be more convienent when I am on the roof. thanks for the help.

I just checked a roll of 300 Ohm I have laying around and it's labeled:

Channel Master Polyclad Model 9354

So you think the really thin wire from fry's is acceptable and use it with crimps for a better connection?
I personally dont like to crimp when I could solder.

Well this morning right after sunrise the Peachtree channel that wouldn't come in at all was coming in just fine at 9/12 bar signal.

I'm looking at
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html
and wondering what the deal is. "Combiner" means
using a splitter backwards, right? Thus the 0.5 dB loss.
Can someone explain *why* this results in more gain than
the factory setup? Does impedance play a role here?

Do the 4228 and DB8 use the same setup as the 8800?
The 8800 is a bit weak in the channel 40-50 range,
would switching to 2 baluns and a combiner help?

How accurate are these models? The HD-7698P graph
bounces up and down wildly, which seems unlikely.
Yes it says the model is still in development, but
I've seen similar oddness on other graphs which
have (I assume) models that are considered mature.

Yeah. But one of the advantages of that design is that it exhibits a very wide beam pattern for its gain compared to other 10dbi antennas.

When you stack two identical antennas together and do it right, you should expect about 2.5 dbi increase in gain (3 dbi is theoretical). AFAIK, AD is changing their marketing literature to show about 12.5 dbi gain on the CS4. The 4228HD as shipped, is worse than the old 4228, per Ken Nist. I havent looked at the DB-8, I rather look at mclapps 8 bay, heh.

According to Ken's latest "temporary" simulations, it looks like Antennas Direct is spot-on with their gain claims with the CS2. It appears that the "out-of-the-box" 4228HD still beats 12.5 dbi across most of the 14-51 band though, but its beam pattern is still probably narrower than the CS4.

I have a classic 4228 with the cross-feedline removed and replaced with two baluns and a splitter. It was in my attic and was thinking about putting it on my roof, but I need to make sure it's quite watertight first.

Added a 24db amp to my DB2 and voila! Much better reception of the stations I can receive. w00t.

The 0.5 dB loss is optimistic in my experience. To get a loss in this range you need to use a stripline combiner costing around a hundred bucks. I measured several 2 and four port splitters in pairs on channel 51. This gives no change in impediance and you get the sum of the two losses for each pair. In all the cases where I used the small cast metal ones with little transformers in them I got a loss of 5 dB. Meaning each one used as a combiner would lose 2.5 dB.

A miss match in impedance will result in only part of the received signal getting into the coax and preamp/receiver. The accuracy of the models could be verified by someone trying the modification and measuring the increase in receive level. Be neat if someone with one tried it.
John



I'm looking at
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html
and wondering what the deal is. "Combiner" means
using a splitter backwards, right? Thus the 0.5 dB loss.
Can someone explain *why* this results in more gain than
the factory setup? Does impedance play a role here?

Do the 4228 and DB8 use the same setup as the 8800?
The 8800 is a bit weak in the channel 40-50 range,
would switching to 2 baluns and a combiner help?

How accurate are these models? The HD-7698P graph
bounces up and down wildly, which seems unlikely.
Yes it says the model is still in development, but
I've seen similar oddness on other graphs which
have (I assume) models that are considered mature.

>> And yes, some TV stations transmit bogus data streams.
>> Sometimes bogus enough to crash the mpeg decoder.
>
> Any purpose as to why they do this ?

The problems caused by the bogus datastreams often resemble
reception problems. If you are into conspiracy theories,
I suppose maybe someone owns stock in the cable/sat companies?

Example:
http://g.imagehost.org/0284/Big_Bang_Theory_64_perfect_reception.png

But there is that quote about never assuming malice for things
that can be explained by incompetence, so I'm assuming incompetence.

The 0.5 dB loss is optimistic in my experience. To get a loss in this range you need to use a stripline combiner costing around a hundred bucks. I measured several 2 and four port splitters in pairs on channel 51. This gives no change in impediance and you get the sum of the two losses for each pair. In all the cases where I used the small cast metal ones with little transformers in them I got a loss of 5 dB. Meaning each one used as a combiner would lose 2.5 dB.

A miss match in impedance will result in only part of the received signal getting into the coax and preamp/receiver. The accuracy of the models could be verified by someone trying the modification and measuring the increase in receive level. Be neat if someone with one tried it.
John

I used the same joiner on both VHF and UHF. On VHF stacking helped. I had more loss on UHF.

I have been thinking, that antennas would be MUCH less visually obtrusive if the color of the elments weren't so darn BRIGHT and SHINY. the reflector grids of the XG-91 with that gun metal tone practically dissappear on my roof... isn't there any way to make the rest of the elements that same color? Elements are anodized, right? Any type of chemical antiquing process or spray application that would darken the elements to a graphite or gun metal color? Without affecting the performance in any way, of course!!! Of course, one COULD paint the boom (not getting any on the elements) a nice, dark color, and that would HELP... but any suggestions to darken the elements?

As long as the covering is non-conductive it should have little effect. The dielectric properties might shift the resonant frequency somewhat but given that these antennas are fairly broadband it shouldn't be noticeable.

The most difficult problem will be finding something which survives UV and weather. You might need to reapply occasionally. You probably don't need to have 100% coverage to achieve the desired result. Just a light dusting would probably work.

good luck

jtm

You could cover the antenna with a camouflage net.

Sorry if this has been covered before. I wasn't able to find the answer with the search facility.

I have an attic-mounted CM4228 feeding a TiVo HD. I would like to add a preamp but also split the feed to support another tuner and a SiliconDust HDHomeRun.

My understanding is that either:
(1) It's best to split the feed after the output of the power injector, but one can split the feed between the pre-amp and the power injector so long as one uses a special splitter that blocks DC on any terminal not inline between the power injector and the preamp.
...or...
(2) The feed should never be split until after the power injector because it doesn't work (at all/as well).

I have some aesthetic and cabling issues that would make a split between the injector and the pre-amp really helpful. If the in-between split works, is there a favored splitter (or preamp/injector/splitter combination) known to work well?

My alternative will have to be to mount the power injector in the attic. If I end up going that route, are there any models I should be thinking of given the wide spread in operating temperature?

Thanks for your attention.

A power passing splitter will work. Try to get one that passes power on one leg only. If not, place a DC block on the other leg.

I'm looking at
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html
and wondering what the deal is. "Combiner" means
using a splitter backwards, right? Thus the 0.5 dB loss.
Can someone explain *why* this results in more gain than
the factory setup? Does impedance play a role here?


In an ideal situation, the signals from the two halves of the antenna travel along the phasing wire to the balun and onto the coax. In the real situation, several bad things can happen

1) Impedance mismatch between the phasing harness and antenna half. This will cause power to be reflected from the phasing harness back out the antenna.

2) Impedance mismatch between the phasing harness and the balun. This will cause power to be reflected back along the phasing harness.

3) The phasing harness can directly radiate power.

The HDTVPrimer guy has said that the old 4228 harness radiates power.

Will an antenna like the HD7694P pick up a channel from the rear? I need to pick up channels at 21, 28, 31, and 224 degrees. Another channel at 261 degrees would be nice too.

The signals are pretty good as I can pick them up with an indoor powered loop & bunny ears pointed out a window.


Also, what kind of mount should I use to mount the HD7694P at the peak of the roof? I've been looking at eave mounts and j-mounts, but couldn't find a max weight of either. I'd hate for the bolts to get ripped out with some wind.

Anyone find a CM-2020 shipping yet? Nothing in my web searches.

tnx
jtm

As long as the covering is non-conductive it should have little effect. The dielectric properties might shift the resonant frequency somewhat but given that these antennas are fairly broadband it shouldn't be noticeable.

The most difficult problem will be finding something which survives UV and weather. You might need to reapply occasionally. You probably don't need to have 100% coverage to achieve the desired result. Just a light dusting would probably work.

good luck

jtm

Yep, in theory the paint wont affect it much. But Im superstitious and like my antenna wire bare, heh.

Yes, just a light dusting with the spray paint will do the trick and even last longer than a heavy 7 coat job. Just dont paint the balun connection points, heh.

The HDTVPrimer guy has said that the old 4228 harness radiates power.
Yes, its very hard to prevent horizontal phasing lines from acting as part of the antenna. Vertical phasing lines dont have this problem.

The signals are pretty good as I can pick them up with an indoor powered loop & bunny ears pointed out a window.

Keep in mind, those antennas have a figure 8 radiation pattern. The HD7694P is much more directive towards the front.


Also, what kind of mount should I use to mount the HD7694P at the peak of the roof? I've been looking at eave mounts and j-mounts, but couldn't find a max weight of either. I'd hate for the bolts to get ripped out with some wind.
The mounting metal, while thin, is extremely strong. The weak point would be the lag bolts, so use longer ones with washers.

If I want to test how a splitter will effect my antenna signal, do I have to have all TVs/Tuners connected and turned on or can I test with just 1 TV connected and placing a terminator on any open coax connection of the splitter?

If I want to test how a splitter will effect my antenna signal, do I have to have all TVs/Tuners connected and turned on or can I test with just 1 TV connected and placing a terminator on any open coax connection of the splitter?

the splitter will attenuate your signal without connecting anything to the open ports.

But for the most faithful results, use the terminator or connect the other TV. The other TV does not need to be on.

I'm giving up on the CM-2020 search and going instead for a Winegard HD7698P for the attic. Gain is higher anyway which is a benefit.

Any opinions on this unit?

tnx
jtm

Keep in mind, those antennas have a figure 8 radiation pattern. The HD7694P is much more directive towards the front.

Is that a no on picking up the channels 180 degrees apart? Is there a decent outdoor antenna that can work from both directions?

I need VHF for channel 9...

A di-pole. :)

http://www.zorg.org/radio/dipole_antenna.php

Channel RF 9 = 187.25MHz

http://www.wfu.edu/~matthews/misc/dipole.html (http://www.wfu.edu/%7Ematthews/misc/dipole.html)

http://www.educypedia.be/electronics/antennadipole.htm

The problem I see with 300 Ohm twin-lead is that it has a spacing gap of only ¼" on the roll I have.
NOTE: I just ran the calc for ¼" and it didn't show any difference.

Is that a no on picking up the channels 180 degrees apart? Is there a decent outdoor antenna that can work from both directions?

I need VHF for channel 9...

Not necessarily a no, but it depends on how strong the signal is coming from the back. Picking it up with a loop indoors indicates you have a strong signal, but you never know exactly what will happen with a stronger directional antenna until you actually have it up and mounted.

A di-pole The folded dipole has about .75 dbi more in gain.

Hey guys,
Did anyone modify their 4228hd as what Ken did to improve their gains?

I general, the higher the gain of an antenna, the less signal it gets off the back.

I've always gotten good avice here, I am back for more. The digital strength of most of my channels fluctuate what I consider to be broadly, e.g. 35-50%on one channel, 80-90% on another, in a couple seconds. Not much of an issue except in that dropout range for a few channels (25-40%). The antennas are stable (roof mounted ya-1713 and 91xg)-i.e. not moving. Connections and cable seem to be good. I am sure the fluctation reported is a product of the sensitivity of the digital strength meter and output, but what are some causes of this wide fluctuation? Multipath? Just the manifestation of a weak signal stream?

I've always gotten good avice here, I am back for more. The digital strength of most of my channels fluctuate what I consider to be broadly, e.g. 35-50%on one channel, 80-90% on another, in a couple seconds. Not much of an issue except in that dropout range for a few channels (25-40%). The antennas are stable (roof mounted ya-1713 and 91xg)-i.e. not moving. Connections and cable seem to be good. I am sure the fluctation reported is a product of the sensitivity of the digital strength meter and output, but what are some causes of this wide fluctuation? Multipath? Just the manifestation of a weak signal stream?

The signal meter indicates signal quality, which is a function of the decoding errors of the 8VSB modulation bit stream (not signal strength).

Low meter indications can be due to result of older generation ATSC tuners (e.g. not able to compensate for the lost data), low signal strength and/or multipath.

Additionally, while the ATSC standards and 8VSB modulation do have +s and -s, handling dynamic conditions is not a +. While, current 6th generation tuners are much better, the changing dynamics of weather, foliage, wind, and nearby moving objects can cause a lot of havoc (specially in the UHF band).

Following is a link that describes what one person went through to correct multipath (has before and after spectrum analyzer displays). Note that there are 2 pages within this link.

http://www.prism.gatech.edu/~wn17/ (http://www.prism.gatech.edu/%7Ewn17/)

IMHO, reception of multipath (static or dynamic) is, more ofen then not, the culprit.

You seem to be using antennas with very good directionality patterns, which is the 1st line of defense.

Perhaps re-aiming (e.g. to maximize the direct signal and minimize multipath) could be of some benefit.

Additionally, your coax is likely to be part of the antenna system and is picking up some multipath. See post 1957 at:

http://www.avsforum.com/avs-vb/showthread.php?t=798265&page=66

The digital strength of most of my channels fluctuate what I consider to be broadly, e.g. 35-50%on one channel, 80-90% on another, in a couple seconds.
Do you mean fluctuating only 10 to 15% ? Thats pretty much normal on a lot of CECB meters (some will read more steady) due to minor atmospheric changes. Or do you mean going from 50 to 90% in a couple of seconds ? If so, thats something coming between you and the transmitter, like an airplane.

serndipity provided the very interesting URL:
http://www.prism.gatech.edu/%7Ewn17/

I've thought of trying to shield an antenna,
but always assumed that the inside surface would reflect
waves towards the antenna, creating new multipath.
Is there a VHF/UHF absorbing material that the inside
of the shield could be lined with?

Clearly in Bill's case the net result is a major win.
I wonder if this is typical?

serndipity provided the very interesting URL:
http://www.prism.gatech.edu/%7Ewn17/

I've thought of trying to shield an antenna,
but always assumed that the inside surface would reflect
waves towards the antenna, creating new multipath.
Is there a VHF/UHF absorbing material that the inside
of the shield could be lined with?

Clearly in Bill's case the net result is a major win.
I wonder if this is typical?

because the shield is grounded it doesn't act the same as a reflector which is floating.

That type of shielding and making an aperture is extreme but sometimes needed in strong multipath situations.

I've thought of trying to shield an antenna,
but always assumed that the inside surface would reflect
waves towards the antenna, creating new multipath.

That would be my gut feeling too. I would think his design could be made better if the frame were connected by hinges, so that it would be adjustable and could be tweaked in individual situations for best performance.

Like many of you, I experimented with different antennae, purchased and home-built. All of my experiments have been indoor-placed, either above my TV or on the wall to the right of my TV. The antenna is usually facing 180 degrees. I have Dayton to my north, and Cincinnati to my south, so plenty of channel receiving possibilities.

My first antenna was an RCA ANT537. It was an emergency purchase during a week when my DirecTV was down. It was okay. Not great, but it received the PBS stations so my 3-yr old could still watch Thomas the Tank Engine.

Fast forward a year later, to save money, I cancel DirecTV. Over the course of many, many years as a subscriber, my monthly bill had crept up to $92/month. :eek:

And thus, I had to really research this stuff. I next bought the Winegard SS-3000. It was better than the RCA. At this point, I only care about the digital stations, since I have 21 to 24 of them to receive, depending on the antenna and the weather.

I recycled some of my wife's metal coat hangers and experimented with a few designs and variations (SBGH, DB1, DB2, DB4, UHF Loop) and also purchased a pair of Eagle Aspen DB2's. I also picked up a 24db amplifier. Every antenna improved with the amplifier. :D Funny how that happens, eh? I also picked up a spool of 14 ga wire when my wife's coat hangers began to become scarce.

So far, the two best performers have been the Eagle Aspen DB2 and my home-built SBGH. I don't have a meter to show gains and losses, and I am fairly certain that I am suffering from multi-path. I am getting primarily Cinci stations. There are two digital Dayton stations I am not receiving, yet. My brick house is not exactly the most condusive to quality reception indoors.

My next round of experimenting will be in the attic. I am not quite ready for the roof phase.

The design that intrigues me the most, actually, is the UHF Loop. It has been the most omnidirectional experiment I have tried.

The Eagle Aspen works remarkably well in my son's room. He is at the end of the house and easily receives all the important channels without the reflector installed. Why isn't the reflector installed? Manufacturing defect. They forgot to drill one of the reflector attachment holes. :rolleyes: No biggie, I am recycling it for use with other antenna experiments.

All of my home-built designs have been reflectorless.

Going OTA has been great excuse to experiment during this cold weather.

>> I've thought of trying to shield an antenna,
>> but always assumed that the inside surface would reflect
>> waves towards the antenna, creating new multipath.
>> Is there a VHF/UHF absorbing material that the inside
>> of the shield could be lined with?

> because the shield is grounded it doesn't act the same as a
> reflector which is floating.

Why would this apply to a shield but not to the ground itself,
which generates a ground reflection?

>> I've thought of trying to shield an antenna,
>> but always assumed that the inside surface would reflect
>> waves towards the antenna, creating new multipath.
>> Is there a VHF/UHF absorbing material that the inside
>> of the shield could be lined with?

> because the shield is grounded it doesn't act the same as a
> reflector which is floating.

Why would this apply to a shield but not to the ground itself,
which generates a ground reflection?

metal in a metallic shield is affected by the waves strongly, that is why metal is either a good antenna or a shield depending on how it is used.

the earth has various amounts of metal in it, it isn't the same as pure metal in its behavior to radio waves

>> I've thought of trying to shield an antenna,
>> but always assumed that the inside surface would reflect
>> waves towards the antenna, creating new multipath.
>> Is there a VHF/UHF absorbing material that the inside
>> of the shield could be lined with?

> because the shield is grounded it doesn't act the same as a
> reflector which is floating.

Why would this apply to a shield but not to the ground itself,
which generates a ground reflection?
ANYTHING around the antenna will affect it....although conductive materials
are much worse than non-conductive (e.g. dielectric) materials.
All of this can be simulated with a powerful enough version of NEC Sim....and patience....

To reduce multipath, antenna designs use reflectors and directors to maximize
response in the desired direction and minimize response in undesired directions.
So higher gain, higher F/B antennas help to reduce multipath.

Some antenna designs are better at suppressing the rear sidelobes, such as
the 91XG and a super-sized 3-D Corner Reflector, which builds HALF of
a box around the antenna (hint, hint....):
http://www.cebik.com/content/a10/vhf/3c.html
http://www.cebik.com/content/radio.html
FREE registration required.....

Additional shielding can also help, such as constructing a chicken wire "fence"
between the antenna and likely multipath sources. This is perhaps easier to
do in attic locations.....

The Eagle Aspen DB2 is now installed in the attic, 14' from ground level. A channel scan gives me 24 digital channels. The problem child of digitals for me was channel 45.1 and 45.2, they are now crystal clear.

My antenna post in the attic will easily allow me to try my other antenna designs at-will. Somewhere, there is a digital 7 and 9 for me to receive.

The folded dipole has about .75 dbi more in gain.

Really?? Where did you get that info from??

Only thing a folded dipole has over a regular dipole is a higher impedance (typically 300ohms vs 75 but it can be different).....None of my reference books make any claim of gain....and considering a dipole is 2.15dbi. .75more is not much to look at....if it were the case at all.

Really?? Where did you get that info from??

Only thing a folded dipole has over a regular dipole is a higher impedance (typically 300ohms vs 75 but it can be different).....None of my reference books make any claim of gain....and considering a dipole is 2.15dbi. .75more is not much to look at....if it were the case at all.

From modeling a reference UHF folded dipole in NEC2. IIRC, Ive seen that 2.9 dbi figure in some books too. Modeling a plain dipole in NEC2, I get very close to that 2.15 dbi figure. Yeah, .75 dbi is not much, but its something at least, and it may not apply to something like a twinlead folded dipole, which I havent yet modeled.

Any kind of VHF dipole is better than just a plain old UHF antenna. :)

And since there isn't any reflector, you should be able to receive stations 180° from each other.

Of course, a simple yagi will give more gain (ie. Director, Folded Dipole, Reflector).

Has anyone used a "Grid Yagi" for reception? http://home.comcast.net/~ross_anderson/GridYagi.htm

Am I right in assuming that it is a narrow band antenna and can be used for good single station reception?

Any kind of VHF dipole is better than just a plain old UHF antenna. :)

And since there isn't any reflector, you should be able to receive stations 180° from each other.

Of course, a simple yagi will give more gain (ie. Director, Folded Dipole, Reflector).

Has anyone used a "Grid Yagi" for reception? http://home.comcast.net/~ross_anderson/GridYagi.htm

Am I right in assuming that it is a narrow band antenna and can be used for good single station reception?

those hams they're just wacko. his intention is to be narrow band.

it has a wind and ice load. i don't think it would hold it dimensions long.

it's not a yagi and it's not a quad. it is different what ever it is.

My DB2 (with reflector) does a good job of picking of Channel 12.1 (digital 12), but doesn't see WCPO-TV Channel 9 (analog 9) or 9.1 (digital 10). It is a UHF antenna, so I am happy that is sees 12 as well as it does.

Would a DB4 give me a better shot of getting 9.1 without the need of a secondary VHF-only antenna?

Really?? Where did you get that info from??

Only thing a folded dipole has over a regular dipole is a higher impedance (typically 300ohms vs 75 but it can be different).....None of my reference books make any claim of gain....and considering a dipole is 2.15dbi. .75more is not much to look at....if it were the case at all.

I wondered about that as well.

The folded dipole has a acquired something of a complex web of correct and incorrect information surrounding it.

L. B. Cebik did a paper to sort out what it is correct to say about the folded dipole.

http://www.cebik.com/content/a10/wire/fdpl.html

Note: Use the root URL for free registration to this treasure of antenna information.

The bottom line was that the folded dipole does not have any more gain than a dipole antenna.

Could you imagine someone stacking two of those on their tower? :D

Two garbage cans on a tower. All you need then, is a mobile home next to it.

serndipity provided the very interesting URL:
http://www.prism.gatech.edu/%7Ewn17/

I've thought of trying to shield an antenna,
but always assumed that the inside surface would reflect
waves towards the antenna, creating new multipath.
Is there a VHF/UHF absorbing material that the inside
of the shield could be lined with?

Clearly in Bill's case the net result is a major win.
I wonder if this is typical?

I have one low-power VHF-HI (channel 8) digital station currently, with four more
full-service VHF-HI digital stations to appear in June. I am using a roof-mounted
Channel Master CM-4221 4-bay. To improve VHF-HI gain, I replaced the 20" wide 1"x2"
mesh reflector with a 36" wide 1"x2" mesh reflector. My experiment was a success,
and I can now receive channel 8 with a Zenith DTT901, although the signal-level is
very low. The signal-level of the existing analog VHF-HI stations also improved, and I
appear to have sufficient VHF-HI antenna gain for the full-service stations in June.

I have one more CM-4221 to modify, and I am wondering if there are better alternatives.
For example, if you look at various yagi design sites, the Driven Element/Reflector
distance for a 180 MHz (channel 8) antenna varies between about 9 3/4" (ARRL) and 13"
(DL6WU), depending on the model. The Driven Element/Reflector distance on my CM-4221
is only 4.5"! Should I have left the CM-4221's existing 20" wide reflector, and placed
a second VHF-HI reflector (horizontal rods would be sufficient) 5" to 8" behind the
original reflector?

I don't have the computer equipment or expertise to model antennas, so I thought I
ask here. Has anyone modeled adding a VHF-HI reflector behind a standard 4-bay reflector?
Or, modeled adding a VHF-HI reflector to a UHF corner-reflector yagi, such as a U-75R?

Two garbage cans on a tower. All you need then, is a mobile home next to it.roflol

I have one more CM-4221 to modify, and I am wondering if there are better alternatives.


Arbie,

Check out the thread in this forum entitled "how to build a uhf antenna". There are plans for a mclap 10 x 9.5 4-bay that has excellent uhf reception and will acquire high vhf channels. The bays are 9.5 inches apart and the whiskers are 10 inches long. Works very well!


mclapp's info is available here: http://www.frontiernet.net/~mclapp/Antennas/

HTH

Rick

To improve VHF-HI gain, I replaced the 20" wide 1"x2"
mesh reflector with a 36" wide 1"x2" mesh reflector. My experiment was a success,
and I can now receive channel 8 with a Zenith DTT901, although the signal-level is
very low.

I may have to try this with my DB2 to try and pick-up DTV 10.

roflol

ya, just ya... LOL

I had another thought come to mind. I am going to try my Winegard SS-3000 antenna up in the attic. It had shown promise in receiving VHF-Hi before I began experimenting with the DB2.

> metal in a metallic shield is affected by the waves strongly,
> that is why metal is either a good antenna or a shield depending
> on how it is used.

IIRC, I've read complaints about reflections from a water tower.
Presumably grounded metal.

To fully enclose the shield, (to keep the snow, birds, etc. out)
you could try and find a plastic garbage can lid that fits the
metal can. Or fabricate one from fiberglass.

For lighter weight and to avoid the trailer jokes, you
could make the shield (and the antenna itself) from carbon
fiber nanotubes.

http://deviceace.com/science/331/cnt-threads-can-transmit-radio-signals-and-could-replace-copper-wires.html

Of course if it is in your attic, no one will see it.

Any kind of VHF dipole is better than just a plain old UHF antenna. :)

And since there isn't any reflector, you should be able to receive stations 180° from each other.

Of course, a simple yagi will give more gain (ie. Director, Folded Dipole, Reflector).

Has anyone used a "Grid Yagi" for reception? http://home.comcast.net/~ross_anderson/GridYagi.htm

Am I right in assuming that it is a narrow band antenna and can be used for good single station reception?
Most Yagi's are designed for narrow band use. Typical "single channel" Yagi's
for TV band only cover about 1 channel (Ch2-6), maybe 3 channels (Ch7-13)
and as many as 6-12 channels (UHF) (fewer at low freqs):
http://www.hdtvprimer.com/ANTENNAS/WadeSCY.html
http://www.blondertongue.com/reception/bty.pdf

I'ld hate to see the damage that beast can cause when a big wind blows through....
And some people complain about the CM4228 being a huge sail....

A friend of mine saw my DBGH the other day and asked about my "Bed Spring" antenna. :D

These digital channels need to pump up their power output. I am beginning to miss my DX'ing, and trying to capture the Metro Detroit at over 100+ miles is a challenge.

I sure hope I don't talk myself into raising the tower 20' higher. Might go to a quad stack, as this is getting frustrating.

I have stacked 2 CM4228s vertically to improve my reception of stations that are 80-100 mi away. The cm4228s are combined using a 2-way splitter/combiner into a cm7777. My elevation is 1100 ft so I usually get good reception since most stations are LOS but I have some stations that are marginal and I would like to try and improve the signal reception.

I read in the HDTVprimer site that the cm4228 suffers from a bad design for the feedlines connecting the two 4-bay halves. The author suggests replacing the feedlines with two baluns, two identical coax lines and a splitter used as a combiner to reduce the losses. If I wanted to do something like this in my setup would it be better to use two separate 2-way splitters into another 2-way splitter/combiner or one 4-way splitter to combine signals from all four 4-bay sections?

This seems like a one way change since removing the feedlines doesn't seem reversible. Does it make sense to make this kind of mod to the cm4228? I haven't seen a report from anyone who has done this kind of mod so I'm not sure that the basic idea is practical.

Any advice?

I read in the HDTVprimer site that the cm4228 suffers from a bad design for the feedlines connecting the two 4-bay halves.

Any advice?

The author was talking about the new 4228 HD, not the original design.

I have stacked 2 CM4228s vertically to improve my reception of stations that are 80-100 mi away. The cm4228s are combined using a 2-way splitter/combiner into a cm7777. My elevation is 1100 ft so I usually get good reception since most stations are LOS but I have some stations that are marginal and I would like to try and improve the signal reception.

I read in the HDTVprimer site that the cm4228 suffers from a bad design for the feedlines connecting the two 4-bay halves. The author suggests replacing the feedlines with two baluns, two identical coax lines and a splitter used as a combiner to reduce the losses. If I wanted to do something like this in my setup would it be better to use two separate 2-way splitters into another 2-way splitter/combiner or one 4-way splitter to combine signals from all four 4-bay sections?

This seems like a one way change since removing the feedlines doesn't seem reversible. Does it make sense to make this kind of mod to the cm4228? I haven't seen a report from anyone who has done this kind of mod so I'm not sure that the basic idea is practical.

Any advice?

Caution! I stacked two antennas a couple of years ago with info from this site(combiners, equal cable lengths,etc.). Not that the info from here was wrong but most of my signals were worse after stacking. A waste of time and money. It might not be the magic bullet as it can be for others.

My DB2 (with reflector) does a good job of picking of Channel 12.1 (digital 12), but doesn't see WCPO-TV Channel 9 (analog 9) or 9.1 (digital 10). It is a UHF antenna, so I am happy that is sees 12 as well as it does.

Would a DB4 give me a better shot of getting 9.1 without the need of a secondary VHF-only antenna?

Probably not since you're somewhat far from the transmitters in downtown Cincinnati. How does analog 12 look? They're moving their digital signal from RF 31 back to RF 12 in the next few months, so you may lose 12 at that point too.

Caution! I stacked two antennas a couple of years ago with info from this site(combiners, equal cable lengths,etc.). Not that the info from here was wrong but most of my signals were worse after stacking. A waste of time and money. It might not be the magic bullet as it can be for others.

Unless you've moved recently, your current location is semi-urban and relatively close in to your transmitters. If your goal was to combat multipath then horizontal stacking would have been the way to go and probably unamplified (or at most using a low gain/hi input capability amp). If you stacked vertically, I'm not surprised you didn't see improvement.

The key to getting the expected gain from stacking, as well as doing all in rcodey's post, is to use combiners that have low loss. The small ones sold as splitters lose about as much as the two antennas gain you. The way to get a combiner without as much loss is to use a stripline combiner or for two antennas quarter wave sections of 96 ohm coax into a tee.
In the case of combining four sections a single four way unit is more likely to have less loss than pairs of two into two would give.
John

Probably not since you're somewhat far from the transmitters in downtown Cincinnati. How does analog 12 look? They're moving their digital signal from RF 31 back to RF 12 in the next few months, so you may lose 12 at that point too.

Yeah, I noticed that. I am going to pick up a DB4 and a antenna pre-amp to help boost signal even more. My attic doesn't room have the room for a DB8. Well, it might, but the bottom of the antenna would have to sit on the attic floor. If I must, I will use a Winegard CC7870 to combine two highly directional antennas (one to Dayton, one to Cincinnati). But, so far, I have been getting by with the omnidirectional capability of the DB2.

I enjoyed trying to build the antennae myself, but the end result just isn't as good at the commercial products. My amateur antenna building is...amateur. :p

The key to getting the expected gain from stacking, as well as doing all in rcodey's post, is to use combiners that have low loss. The small ones sold as splitters lose about as much as the two antennas gain you. The way to get a combiner without as much loss is to use a stripline combiner or for two antennas quarter wave sections of 96 ohm coax into a tee.
In the case of combining four sections a single four way unit is more likely to have less loss than pairs of two into two would give.
John

What you say is of course true, but it also depends on the goal you are trying to achieve with stacking. If the goal is narrower beamwidth to combat multipath, it may still improve the overall signal even with the combiner loss. In most instances, horizontal stacking will work much better at this (unless the reflections are from above or below).

Using a 4 way wide-band splitter as a quad combiner not only has more loss, it just plain won't work in my experience. Using 3 two-way splitters as combiners does at least work but not as well as a 4-way stripline combiner.

Unless you've moved recently, your current location is semi-urban and relatively close in to your transmitters. If your goal was to combat multipath then horizontal stacking would have been the way to go and probably unamplified (or at most using a low gain/hi input capability amp). If you stacked vertically, I'm not surprised you didn't see improvement.

I stacked horizontially with the goal to combat multipath. I tried runs w/o an amplifier with bad results. Members at the time said it is not unusual to have my results. I've thought that the best results might be using the two antennas in different hot spot locations( good signals in one location for some channels and good spot for other signals in other location on roof) and just use an A/B switch with remote.

I wondered about that as well.

The folded dipole has a acquired something of a complex web of correct and incorrect information surrounding it.

L. B. Cebik did a paper to sort out what it is correct to say about the folded dipole.

http://www.cebik.com/content/a10/wire/fdpl.html

Note: Use the root URL for free registration to this treasure of antenna information.

The bottom line was that the folded dipole does not have any more gain than a dipole antenna.

Whoops, my memory is slipping. I went back and checked the model. The Raw gain at 605 Mhz is 2.29 dBi and the SWR is 1.03992. I knew it had that 9 in it somewhere, heh. So its .14 dbi better than a straight dipole.

Here is the Nec File
===============

CM
CE
SY l=0.221 'l = 221mm = 605MHz Folded-Dipole (Mid point of Ch36)
SY y=0.0254
SY h=0.05
SY x=0.0127
GW 1 5 0 -y/2 -h/2 0 y/2 -h/2 0.0015875
GW 2 17 0 -y/2 -h/2 0 -(l/2-x) -h/2 0.0015875
GW 3 17 0 y/2 -h/2 0 l/2-x -h/2 0.0015875
GW 4 4 0 -(l/2-x) -h/2 0 -l/2 -(h/2-x) 0.0015875
GW 5 4 0 l/2-x -h/2 0 l/2 -(h/2-x) 0.0015875
GW 6 5 0 -l/2 -(h/2-x) 0 -l/2 h/2-x 0.0015875
GW 7 5 0 l/2 -(h/2-x) 0 l/2 h/2-x 0.0015875
GW 8 4 0 -l/2 (h/2-x) 0 -(l/2-x) h/2 0.0015875
GW 9 4 0 l/2 (h/2-x) 0 l/2-x h/2 0.0015875
GW 10 40 0 -(l/2-x) h/2 0 l/2-x h/2 0.0015875
GE 0
GN -1
EK
EX 0 1 3 0 1 0
FR 0 0 0 0 605 0
EN

A friend of mine saw my DBGH the other day and asked about my "Bed Spring" antenna.
I get comments from the neighbors about my space invaders sculptures, heh.

The author was talking about the new 4228 HD, not the original design.

He was talking about the original cm4228:

http://www.hdtvprimer.com/ANTENNAS/cm4228.html

Caution! I stacked two antennas a couple of years ago with info from this site(combiners, equal cable lengths,etc.). Not that the info from here was wrong but most of my signals were worse after stacking. A waste of time and money. It might not be the magic bullet as it can be for others.

My experience with the vertically stacked cm4228s is that I got about 2db more gain which allowed me to receive a marginal station more regularly (5% -> 30% of the time). If replacing the feedlines could get me enough to receive the marginal station more regularly (say 75%) then maybe it's worth the trouble. Another idea is to use an ultra low noise preamp like the Research Communications.

What you say is of course true, but it also depends on the goal you are trying to achieve with stacking. If the goal is narrower beamwidth to combat multipath, it may still improve the overall signal even with the combiner loss. In most instances, horizontal stacking will work much better at this (unless the reflections are from above or below).

Using a 4 way wide-band splitter as a quad combiner not only has more loss, it just plain won't work in my experience. Using 3 two-way splitters as combiners does at least work but not as well as a 4-way stripline combiner.

Where can I get a 4-way stripline combiner?

John

Where can I get a 4-way stripline combiner?

John

Lindsay used to sell/make them but no more.

Here's the "new" source:

http://www.hamtv.com/oal.html

Be sure to specify the frequency band and 75 ohm connection.

Pic below courtesy of MaxHD.

I stacked horizontially with the goal to combat multipath. I tried runs w/o an amplifier with bad results. Members at the time said it is not unusual to have my results. I've thought that the best results might be using the two antennas in different hot spot locations( good signals in one location for some channels and good spot for other signals in other location on roof) and just use an A/B switch with remote.

Properly done, horizontal stacking should provide higher gain and narrower beamwidth. This means higher performance assuming no other mitigating factors and you are setup/aimed properly. Therefore, I would heartily disagree with the "members" that poorer performance resulting from horizontal stacking would not be unusual. I think it would be very unusual and I suspect something was not set up properly.

It's like saying you put up a CM 4221 and it outperformed a CM4228.

Properly done, horizontal stacking should provide higher gain and narrower beamwidth.
With horizontal stacking, depending on the stacking distance, you can induce lobes that can take away from the main direct forward lobe, hence the seemingly poor performance. With vertical stacking, you dont have that problem.

http://www.hdtvprimer.com/ANTENNAS/ganging.html

These digital channels need to pump up their power output. I am beginning to miss my DX'ing, and trying to capture the Metro Detroit at over 100+ miles is a challenge.

I sure hope I don't talk myself into raising the tower 20' higher. Might go to a quad stack, as this is getting frustrating.

The FCC has severely limited the power of digital signals. People living any longer distance from the broadcast antenna can’t make their converter boxes or expensive new TV’s work. If the FCC had allowed the digital signals to be just as strong as the analogs, anyone with even marginal analog reception would have been able to get crystal clear digital stations. The exceptions would include those who were watching analog stations with visible “ghosts”. It isn’t right to be robbing rural viewers of free tv IMO.

With horizontal stacking, depending on the stacking distance, you can induce lobes that can take away from the main direct forward lobe, hence the seemingly poor performance. With vertical stacking, you dont have that problem.

http://www.hdtvprimer.com/ANTENNAS/ganging.html

Hence, the wording "properly done". As spacing increases, the forward gain increases but you also increase the side lobe gain. Even wider, and the forward lobe can actually be less than the side lobes and the side lobes can multiply. What you typically want is a large forward lobe, deep adjacent null, and sidelobes that aren't so large as to interfere with the signal. Experimentation with spacing may be necessary to find the best balance overall in a particular location/installation.

I don't see why it would be any different with vertical stacking. You'd simply induce vertical lobes instead.

I sure hope I don't talk myself into raising the tower 20' higher.

It might not be enough.

I've got my 4228 at 125' and still didn't get anything from Burlington, VT.

That must be one heck of a climb for maintenance. :D

Hence, the wording "properly done". As spacing increases, the forward gain increases but you also increase the side lobe gain. Even wider, and the forward lobe can actually be less than the side lobes and the side lobes can multiply. What you typically want is a large forward lobe, deep adjacent null, and sidelobes that aren't so large as to interfere with the signal. Experimentation with spacing may be necessary to find the best balance overall in a particular location/installation.

I don't see why it would be any different with vertical stacking. You'd simply induce vertical lobes instead.

Believe the spacing I used was 36" on the Televes.

Lindsay used to sell/make them but no more.

Here's the "new" source:

http://www.hamtv.com/oal.html

Be sure to specify the frequency band and 75 ohm connection.

Pic below courtesy of MaxHD.
Re LOW-LOSS STRIPLINE COUPLERS:

None of those covered any part of the TV bands.....
Can you order a stripline combiner for the entire UHF band...and/or Hi-VHF?

Telewave (San Jose, CA) stocks PARTIAL UHF BAND (Ch14-35) 2/3/4-port
stripline combiners (ANTPD24=$135, ANTPD34=$202, ANTPD44=$218):
http://www.tessco.com/products/displayProductInfo.do?sku=10998&eventPage=1
http://www.hol4g.com/ac/product.aspx?number=TEL-ANTPD24&p=163774&sc=3634
http://www.hol4g.com/ac/product.aspx?number=TEL-ANTPD34&p=159829&sc=3634
http://www.tessco.com/products/displayProductInfo.do?sku=74570&eventGroup=4&eventPage=1
[About 8.5-inches long....]

Telewave also sells on-line, see entire line here...note UHF band gap:
http://www.telewave.com/pricelist/powerdiv.html
http://www.telewave.com/pdf/Telewave_Pricelist_2008.pdf
Perhaps they have some additional products???

Kathrein/Scala also makes PD2-LLN, PD3-LLN and PD4-LLN stripline combiners,
but they only operate on UHF Ch14-19...perhaps they have another suitable product???

===================================
Telewave stocks Hi-VHF (except Ch13) 2/3/4-port stripline combiners
(ANTPD21=$149, ANTPD31=$210, ANTPD41=$224):
http://www.hol4g.com/ac/product.aspx?number=TEL-ANTPD21&p=161679&sc=3634
http://www.hol4g.com/ac/product.aspx?number=TEL-ANTPD31&p=166385&sc=3634
http://www.hol4g.com/ac/product.aspx?number=TEL-ANTPD41&p=170482&sc=3634
[About 8.5-inches long....]maybe they can extend it for Ch13???]

====================================
Telewave stocks ANTPD208 (2-port, $200) CH4-6 Lo-VHF stripline combiner:
http://www.hol4g.com/ac/product.aspx?number=TEL-ANTPD208&p=168682&sc=3634
ANTPD308 (3-port, $241) and ANTPD408 (4-port, $263) also available.
[Nearly 40-inches long....]

And even the Telewave ANTPD206 (2-ports, $235) for the Ch2-4 Lo-VHF band:
http://www.telewave.com/pdf/TWDS-7099.pdf
[About 51-inches long....]

====================================
Triax (in U.K.) makes full-band UHF as well as Hi-VHF combiners (see pg59):
http://www.triax.co.uk/upload/gb_-_triax_main_catatalogue_2008_[screen]_001.pdf
You'll have to email them to find a distributor (prob. in U.K.):
http://www.triax.co.uk/ServiceSupport/UK%20Distributors.aspx
But I have not seen any confirmation that they are truly STRIPLINE couplers
and they are no longer available at the usual U.K. retail websites, and can not
be found via SEARCH at Triax website.....

====================================
From the pictures you should be able to readily identify a low-loss stripline
combiner by the extended LENGTH.....and PRICE....

Anything the size of a typical $2 splitter/combiner may claim 0.5 dB loss...
but inside it's a hybrid transformer which will have 3 dB additional loss
when used as a splitter (unlike a stripline) and will suffer from gain & phase
MISMATCH losses when used as a combiner (unlike a stripline).

I don't see why it would be any different with vertical stacking. You'd simply induce vertical lobes instead.
Correct, and nobody cares about the up and down direction, heh.

I've got my 4228 at 125' and still didn't get anything from Burlington, VT.
Holy moley, heh. :eek:

That must be one heck of a climb for maintenance. :D

Some people jog. I climb my tower.

Re LOW-LOSS STRIPLINE COUPLERS:

None of those covered any part of the TV bands.....
Can you order a stripline combiner for the entire UHF band...and/or Hi-VHF?



Yes. They will make to order. The pic I attached is a wide band uhf model.

Correct, and nobody cares about the up and down direction, heh.

Well, that's the whole point really. Vertical stacking narrows beamwidth in the vertical plane and can thus create vertical side-lobes/nulls. Horizontal stacking narrows the beamwidth in the horizontal plane and in the process horizontal side lobes/nulls are created.

If you look at a CM4221 it is 4 vertically stacked bowties. Forward gain is decent and beamwidth is fairly large. A CM4228 is basically two horizontally stacked 4221's. A 4228 will have both horizontal and vertical sidelobes but will also have narrower horizontal beamwidth and higher forward gain than a 4221.

I've gotten very comfortable wrapping my leg through my 40' tower, so as to have two hands free. When I work at the very top, I wrap a rope around me (four or five times) and tie it off on the tower (like a cradle). I feel like a baby in it's mothers arms. :)

I don't think I'll have any trouble with 60', when I get the other sections.

I don't think I'll have any trouble with 60', when I get the other sections.

Did you run your tvfool prediction at 60' and compare it to your 40' data? You may find less difference than you expect.

I've gotten very comfortable wrapping my leg through my 40' tower, so as to have two hands free. When I work at the very top, I wrap a rope around me (four or five times) and tie it off on the tower (like a cradle). I feel like a baby in it's mothers arms. :)

I don't think I'll have any trouble with 60', when I get the other sections.

Body parts aren't very reliable for support. A wasp flying up your pant leg might cause you to do some very unsafe things.

Always use a safety strap...always...

jtm

A wasp flying up your pant leg might cause you to do some very unsafe things.I ran across a wasp nest inside a rotator once. It's no fun getting caught off guard up on the roof.:eek:

you look at a CM4221 it is 4 vertically stacked bowties. Forward gain is decent and beamwidth is fairly large. A CM4228 is basically two horizontally stacked 4221's. A 4228 will have both horizontal and vertical sidelobes but will also have narrower horizontal beamwidth and higher forward gain than a 4221.
Yep, Ive modeled all that crap, heh.

ran across a wasp nest inside a rotator once. It's no fun getting caught off guard up on the roof.
You wuss. Thats nothing compared to a hornets nest, heh.

You wuss. Thats nothing compared to a hornets nest, heh.Thank god they make a bigger nest.:D

Some people jog. I climb my tower.
OK, since youre that kind of an insane antenna hobbyist (in my own vain), why dont you build one of my Quad Double Bay GHs designs and see what you get, heh.

If you die installing it, IT IS NOT MY FAULT. (disclaimer)

Also the standard disclaimer, do not install when drunk and dont throw antenna at spouse, heh.

While installing a Primestar system, I trenched open a Yellow Jack nest. They don't quit! No matter how far you run.

I then came across a mud wasp nest under the porch. Then, when I opened the phone demark, I found a Paper Wasp nest. It was a bad day.

What's up with the http://www.TVFool.com/ website, since Feb. 17th? The pre-transition reports are all wacked. Were the reports not adjusted for the change?

Thank god they make a bigger nest.:D

But the distance you have to maintain is far, far greater, heh.

When I go to 60', I get WVPY-DT as an LOS (instead of single-edge), and a minimum of 1dB gain for all of the non-LOS stations (Altoona, Harrisburg-York-Lancaster, Baltimore, and D.C.). Several stations are 1.5dB gain, with a couple giving me 2.5dB of gain.

My Bumble Bees (Wood Boring Bees) keep the Wasps at bay. :)

Believe the spacing I used was 36" on the Televes.


57 inches was what I arrived upon after multiple experimentation. It also happens to be the recommended horizontal stacking distance from the manufacturer:
http://www.televes.com/hojastecnicas/103758.pdf

It is also the distance you come up with when using this calculator:http://www.astronwireless.com/topic-archives-stacking-yagi-antennas.asp

At that width, a rotator is nearly mandatory for proper aiming as the beamwidth is around +/- 5 degrees or even less.

FYI Televes re-worked the DAT75 a couple of years ago. If you happened to get two different antennas (or two different baluns) then phasing would be impossible without accounting for it. The PCB baluns are different b/w the models and the internal trace length differs by about 5.5 inches IIRC. The later model has a much larger reflector.

My Bumble Bees (Wood Boring Bees) keep the Wasps at bay. :)

Ahh, you have cedar boards around. They love that !

It might not be enough.

I've got my 4228 at 125' and still didn't get anything from Burlington, VT.

Tower Guy, what tower have you got? Any pictures?

Body parts aren't very reliable for support. A wasp flying up your pant leg might cause you to do some very unsafe things.

Always use a safety strap...always...

jtm

Agreed, I bought a full body harness, positioning strap, and a "Y" lanyard with large caribeaners for the climb up... 100% attachment... I messaged with Riley, the host of World's Toughest Fixes and he said, even at 25-30ft AGL, one should ALWAYS practice 100% attachment.... (people think that 2000ft is soo much more dangerous, then 35ft, but a fall from 30+ft, will prolly be ones last...)

125'? Where would one live to be able to put a 125' tower in their backyard?

Any pictures?

Yeah really. I got about a 100ft sequioa nearby that Im considering mounting my antennas on. But a 125ft tower beats me, heh. It will take a good five more years to get to that height.

http://img9.imageshack.us/img9/732/dscn0714486x648364x486.jpg

heh. It will take a good five more years to get to that height.

rofl :)

So, where is the point of diminishing returns on the number of bow-ties in a vertical stack? With that 100' sequoia, you could mount a DB32? Or an 8-high GH? ;) Or maybe mount one antenna per channel specifically designed just for that channel and gobs of channel isolaters. :)

Tower Guy, what tower have you got? Any pictures?

It's 120' of Rohn 45. The rotor is on old Ham-m. The feedline is 3/4" jacketed CATV hardline.

I just did a google search for Rohn 45 towers. Wow! I could never climb that thing to the top.

.750" coax! I'll bet you had fun mounting that to 125'. I use to install that stuff for data communications and CATV systems. Do you use a drill to prep or do you use hand tools?

My tower is made by American Tower and is considered a step tower (some call it a ladder tower). There's plenty of area for locking myself in. I use pouches for small items and rope to raise larger items. I was tower qualified with the Army in the 80's.

http://www.amertower.com/residential_towers.html
http://www.solidsignal.com/prod_display.asp?PROD=AMERTOW40

.750" coax! I'll bet you had fun mounting that to 125'.

I used my garden tractor (Bolens G154) and 3/8" nylon rope to pull it up. I hold the tag line while driving in reverse. The 10' tower sections went up the same way.

I also have an electric winch with 1/8" aircraft cable, but the garden tractor is easier.

The end prep of the 3/4" hardline was done by hand.

I used my garden tractor (Bolens G154) and 3/8" nylon rope to pull it up. I hold the tag line while driving in reverse. The 10' tower sections went up the same way.

I also have an electric winch with 1/8" aircraft cable, but the garden tractor is easier.

The end prep of the 3/4" hardline was done by hand.

Very cool, ya, the weight of a section of Rohn 45, would suck for install... I will do my first guyed tower with 25G, just to get in the hang of it... (pun intended)

So, what do you all have up there?

Also, curious, what safety system do you use?

OK, since youre that kind of an insane antenna hobbyist (in my own vain), why dont you build one of my Quad Double Bay GHs designs and see what you get, heh.

Actually I'm trying for more gain than that.

I also need an extremely high front to side ratio to eliminate interference. In my head I've designed a 12' X 8' plane parabolic. The gain will be about mid to high 20 db. The feed would be four bow ties in a row at the focal line of the parabola. I'm working on how to construct the feed.

Very cool, ya, the weight of a section of Rohn 45, would suck for install... I will do my first guyed tower with 25G, just to get in the hang of it... (pun intended)

The big boys call tower building "hanging steel".

I've got my ham radio antennas on my towers.

At 6'5", I'm tall enough to put up 10' tower sections without a gin pole.

Yeah really. I got about a 100ft sequioa nearby that Im considering mounting my antennas on.

How are you planning to mount them?

57 inches was what I arrived upon after multiple experimentation. It also happens to be the recommended horizontal stacking distance from the manufacturer:
http://www.televes.com/hojastecnicas/103758.pdf

It is also the distance you come up with when using this calculator:http://www.astronwireless.com/topic-archives-stacking-yagi-antennas.asp

At that width, a rotator is nearly mandatory for proper aiming as the beamwidth is around +/- 5 degrees or even less.

FYI Televes re-worked the DAT75 a couple of years ago. If you happened to get two different antennas (or two different baluns) then phasing would be impossible without accounting for it. The PCB baluns are different b/w the models and the internal trace length differs by about 5.5 inches IIRC. The later model has a much larger reflector.

They are the same Televes. Shouldn't the closer spacing eliminate the potential problems that I encountered?

The big boys call tower building "hanging steel".
Cool, I have not been around "the big boys" yet, I hope to make the right friends.. Although Riley from World's Toughest Fixes, does not mind talking with viewers...

I've got my ham radio antennas on my towers.
Cool, was wondering if you were a ham.

At 6'5", I'm tall enough to put up 10' tower sections without a gin pole.
Oh, wow, even at 6.5', I would have thought it would have been a pain at 70lbs for Rohn 45G (if the Rohn spec page is correct on weights)

Is this just as a hobby, or do you do tower work professionally?

How are you planning to mount them?

Using very large U staples. Or a couple of holes in the mast to put lag bolts thru. As you can see, the sequioa is a pretty easy tree to climb.

Interesting Article in Communications Technology today:

http://www.cable360.net/ct/news/ctreports/Antennas-Technology-Revisited_34612.html

Enjoy,
Scott

Using very large U staples. Or a couple of holes in the mast to put lag bolts thru. As you can see, the sequioa is a pretty easy tree to climb.

Would you top the tree and put a mast with the antenna on it or just mount the antenna directly to the tree? Wouldn't the swaying of the tree in a storm cause problems? How would the tree's growth affect the mounting over time?

I have some large fir trees that I considered mounting an antenna on but haven't seen any info on how to do that.

John

Yeah you could top it, the firs and sequoia will still grow. The further down the tree, the less the sway. I imagine that the trees growth would bend the mast or pop out the lag screws over time, so it will have to be periodically remounted.

I have seen farmers plant firs about 2 feet apart, then topping them, to form a really nice cow fence / hedge in a few years time.

Interesting Article in Communications Technology today:

http://www.cable360.net/ct/news/ctreports/Antennas-Technology-Revisited_34612.html

Enjoy,
Scott

The FCC digital migration has also redefined the spectrum that channels will be broadcast - from channels 2-69 to 7-69. While this may seem like a small change, its impact on reducing the length of elements required on a traditional rooftop antenna is significant. Eliminating channels 2-6 removes the longest elements on traditional antennas and thus reduces the impact of strong winds and ice on the equipment.

As a result, much shorter antenna elements are needed to receive channels 7-69. (This translates into a reduction in rooftop antenna width from 110 inches to 53.5 inches).


From channels 2-69 to 7-69 ? When did that happen instead of 2 - 51 ? My latest TVFool still shows that Ill have a channel 6 after June.
I really would like 7 - 69 instead of 2 - 51.

From channels 2-69 to 7-69 ? When did that happen instead of 2 - 51 ? My latest TVFool still shows that Ill have a channel 6 after June.
I really would like 7 - 69 instead of 2 - 51.

Channel 5 in Memphis will stay on 5 in June. When did the FCC change their mind?

They are the same Televes. Shouldn't the closer spacing eliminate the potential problems that I encountered?

The closer spacing will give you a wider main forward lobe and much smaller sidelobes. It will also give you less of a deep adjacent null. Wider spacing narrows the main forward lobe, increased the depth of the nulls, but also increases the sidelobes somewhat.

Narrower spacing can make it easier to "catch" Dx signals with the broader beamwidth.

Wider spacing provides the increased directivity needed to combat multipath and also eek out that last bit of gain on a distant signal. The disadvantage is that the extreme narrow beamwidth makes accurate aiming mandatory. A windy day that throws the stack off by only a few degrees could ruin the signal, thus a rotator is needed.

You might double-check the balun numbers on the DATs if you still have them. It's at least possible that the baluns could be mismatched.

Thanks for the advice. As soon as it gets warmer I'll go up the ladder, check the baluns and maybe increase the spacing.

From channels 2-69 to 7-69 ? When did that happen instead of 2 - 51 ? My latest TVFool still shows that Ill have a channel 6 after June.
I really would like 7 - 69 instead of 2 - 51.
Obviously, the CommTech writer (or his editor) was WRONG!!!

The FCC allowed stations to chose to operate on Ch2-6, if they want to.
What is REALLY happening is only 41 stations in U.S. actually chose Ch2-6:
http://www.rabbitears.info/ss/
That's 7 on Ch2, 7 on Ch3, 2 on Ch4, 16 on Ch5 and only 9 on Ch6. So there
is a market for Ch7-13 and Ch7-51 antennas.....in ADDITION to Ch2+ monsters....

In California, the ONLY Ch2-6 DTV is Ch3 in Eureka (near Oregon border).

This could increase when low power DTV station assignments sort out....
Hmm, much lower monthly electricity bill and lots of excess equipment
to chose from at the surplus sales....

And maybe "White Space Devices" will be forced to reconsider Lo-VHF, esp.
for those metro areas that don't HAVE any extra UHF channels....

And it's possible Ch6 is opened to expand FM band....except for perhaps 9 DMAs...

Is this just as a hobby, or do you do tower work professionally?

Just a hobby.

And it's possible Ch6 is opened to expand FM band....except for perhaps 9 DMAs...

Also a good idea. I just want my channel 6 to go to a higher channel number and I dont really care how they do it, heh. Its such an oddball pain for me.

My gut feeling is that these vhf-low stations are holding out for a better deal from the FCC, heh.

Obviously, the CommTech writer (or his editor) was WRONG!!!


You would think that someone in the field like that would get it right. Its not that hard, heh. Wheres he getting his technical info from, the YouTube antenna guy ?? Heh, heh.

It's 120' of Rohn 45. The rotor is on old Ham-m. The feedline is 3/4" jacketed CATV hardline.

Only 120 ft ? In that case I may be up there in only 4 years, heh.

Does anyone know anything about the Alliance Tenna-Rotor? Are they any good?

I've come across one and I noticed that it has four terminals.

If you need a preamp, go ahead and get a VHF+UHF preamp (http://www.channelmaster.com/Pages/TVS/TitanAmp.htm), with a dedicated VHF input. That will make it easy to add a separate VHF antenna later.
do you know what this antenna is

do you know what this antenna isLooks like a Radio Shack VU-90(Channels 2-69 )

Looks like a Radio Shack VU-90(Channels 2-69 )
Yep, that would be my guess too.


Does anyone know anything about the Alliance Tenna-Rotor? Are they any good?

I've come across one and I noticed that it has four terminals.
I still have mine I bought around 1973, and its still working. Ive gotta get around to replacing the five wire cable though, cause its bare in some places, heh. Ive rebuilt and regreased it a few times. Mostly what goes bad from age in it is the non-polarized electrolytic capactor. Its a very simple circuit.
Since you have the four wire one, that means you probably dont have a needle that tells you the direction.

What kind of controller does it use? All I have is the rotor.

What kind of controller does it use? All I have is the rotor.

With the 4 wire model, I believe it used the "clicker" type rotator. My parents had that one in the 50's. You would dial it for the direction you wanted (after the rotor was initially aligned with the right compass point) and it would click step by step until it reached that point. The click was fairly loud, heh.

With my compass needle model, you have to hold the button down (either to the left side or the right depending on the direction you want to go) until it gets to the desired direction. Its quiet.

Does anyone know anything about the Alliance Tenna-Rotor? Are they any good?

I've come across one and I noticed that it has four terminals.

There are different models of the 4-wire tenna-rotor T10, T12, U98, U100 and U110. Are there any numbers on the rotor, or what color is the weather boot on the top. I may have a controller here.

Good point about the model number. I went out and checked mine. I have a model T-45.

There are different models of the 4-wire tenna-rotor T10, T12, U98, U100 and U110.

On the inside of the rotor itself, its just straight wiring to the motor and ground, IIRC. So its likely any of those 4 wire control boxes would work. (Worse case scenario, in reverse)

And the way you wire it up is, one wire in the flat wire group is silver and the others are copper. The silver went on 1 and the rest of the numbers followed what was stamped on the rotor and the control box.

There isn't a weather boot on the rotor. I did see the numbers "02 79" stamped on the bottom of the case. Unfortunately, I don't see any other numbers (except the patent number on the name plate).

Under the cover plate (in really bad shape) for the terminals, there are numbers stamped on the edge.

Upper Left: 1
Upper Right: 2
Lower left: 3
Lower Right: 4

The rotor has six screws holding the case together.

For my location (45056), a reflectorless DB2 is netting me the most digital channels: 24.

I tried a DB1, DB2 and DB4, each with and without reflector panel, each with and without the pre-amp I picked up from solid signal. The one constant was my 28db amplified distributor and my Vizio TV.

So, until I install the J-pole from my previous satellite dish on the roof and go external, the DB2 without reflector and no pre-amp gets me 24 digital channels.

I am in an odd location with Dayton stations being at 51 degrees (average) and Cinci being at 166 degrees (average). In any config, I don't want to use a rotator. Two TVs will eventually be attached to this antenna.

I found it odd that the DB4 lost 22.1 and 45.1/45.2 compared to the DB2 in identical set-up. It must be reflections aiding my reception.

Thus, I am done for the now with the attic experiments. Time to clean up all my antenna gear! The wife has been giving me strange looks regarding my pile-o-antenna.

There isn't a weather boot on the rotor. I did see the numbers "02 79" stamped on the bottom of the case. Unfortunately, I don't see any other numbers (except the patent number on the name plate).

Under the cover plate (in really bad shape) for the terminals, there are numbers stamped on the edge.

Upper Left: 1
Upper Right: 2
Lower left: 3
Lower Right: 4

The rotor has six screws holding the case together.

I may have an Alliance manual somewhere. I will see if I can find it.

Under the cover plate (in really bad shape) for the terminals
Those will definately need to be cleaned up or replaced.

Heh, Norms a little pricey, isnt he. Interesting, the instructions say silver wire on terminal 3, (ground ?) instead of on terminal 1, like I use.

Yeah, my parents had the U-100/110 "clunk clunk" control box plus a double bay vhf bowtie antenna, (single bay shown in the instructions). And its always been HDTV ready, heh.

I think I only paid $23 to $29 for my Alliance unit new back in the 70's. The two downlead from two separate antennas into an A-B switch is a much faster solution for me. The "clunk clunk" control box probably slows the rotor down to 1/3 rpm from its max speed of 1 rpm.

Yeah, the things should last forever with a periodic servicing and replacement of that elec cap. Its pretty easy to service. IIRC, the motor in the rotor is the same as used in old phonograph turntables. My gears werent hardly worn at all.

The fork spade ends are still on the rotor I have and it looks like the silver fork spade is on terminal #3. I did notice that the rotor is stamped with 1 rpm.

I have had this problem happen to me twice now, and I am not exactly sure what caused the problem, so I will try to explain in detail what we did, and what the results were, and how the problem was addressed. But my main question is, why it happened in the first place, because I would like to be able to recognize the situation, and to be able to avoid it in the first place...

First scenario: I have a friend who lives out west of Beaumont, Texas. He bought a RS VU-190 antenna and a RS pre-amp. We installed the antenna up about 36 feet, and when we hooked it up to the converter box or straight to the TV, we got absolutely no channels whatsoever. The tuner was blanked out, like it was overloaded. When the antenna was pointed at 90 degrees to where the local stations were, we were able to get the full power stations on the converter box, but the antenna had to be pointed backwards to get the analogs on the TV.
On the advice of someone I know, I bought a 3dB pad to install before going into the A/B switch so that my friend could toggle back and forth between analog and the converter box. This helped, but he was not able to recieve the digital LP station and still can't.
I originally blamed this on the RS pre-amp and internal noise causing the overload. He lives about 15-20 miles from any full power TV transmitters.

Second scenario: I have a co-worker who lives in the Lake Charles, Louisiana area. Thinking that the RS pre-amp was the cause of the overloading in the original antenna project, I advised him to get a CM 7777 pre-amp. Installation went perfectly. No tuner overload. multiple stations from 3 DMAs from about 30 feet up. He wants to do the same for his dad who lives about a mile from him.

Third scenario: My co-workers dad buys the same set-up. RS VU-190 antenna and CM 7777 pre-amp. 30 feet up.
Hook it up to the converter box... nothing. Nada. Zilch. Take the amp out, locals come in fine, but no distant stations.
His dad decides that the original location for the pole does not suit him, so my co-worker decides to move the antenna to the other side of the house. In the new location, he decides to install the CM 7777 pre-amp back on the antenna, and voila, no overload. Beautiful signals from multiple stations in 3 DMAs.

So... What the heck gives??? Why the overload. No nearby TV or DT transmitters. FM trap in. How do I avoid all the trouble and work of installing an anteanna only to have the tuner blank out? I'm a little gun shy now. Two other installations that I have consulted on went well, one at 16 feet and one at 25 feet.
We are fixing to do one at 20 feet for a friend who lives a couple of miles from my friend in scenario one.
Can onyone give me some insight on what may have caused the tuner overload? I would like any information that might be pertinent. I would like to know what to look for.Thanks.

What do the TV Fool plots look like in each location?

I would avoid high-gain pre-amps, such as the CM7777 in any area that has signals in the green on TV Fool, unless you don't need to point the antenna in the direction of those stations.

TV transmitters at 15-20 miles are rather close, especially if you have LOS.

Do you need Low-VHF? Most areas do not need Low-VHF for DTV and that might save you some headaches. A 7-51 antenna is less cumbersome as well.

Take a look at the last link below. Then follow the link to "Erecting A TV Antenna."

I did notice that the rotor is stamped with 1 rpm.

Yeah, Ive never seen an ad for a rotor faster than 1 rpm. Speed demons they are not, heh.

Yeah, Ive never seen an ad for a rotor faster than 1 rpm. Speed demons they are not, heh.

Do you really want a rotor whipping an LP antenna around quickly? Maybe a DB, they seem fairly durable. :D One of my DB2's has proven to be 3-yr old resistant.

Personally I do, because waiting 20 or 30 seconds can seen like an eternity, heh. Thats why I like the two antennas, two downleads into an A-B switch solution so much.

I can understand that rotors designed for the large 2-69 band antennas would need to move the antenna slowly, but the UHF only and 7-51 antennas are significantly smaller and could be moved at higher speeds. A 3 RPM rotor could certainly work well with the small antennas are take only 10 seconds to do an 180 degree turn.

What do the TV Fool plots look like in each location?

I would avoid high-gain pre-amps, such as the CM7777 in any area that has signals in the green on TV Fool, unless you don't need to point the antenna in the direction of those stations.

TV transmitters at 15-20 miles are rather close, especially if you have LOS.

Do you need Low-VHF? Most areas do not need Low-VHF for DTV and that might save you some headaches. A 7-51 antenna is less cumbersome as well.

Take a look at the last link below. Then follow the link to "Erecting A TV Antenna."

Thanks guys. After studying links provided, I think that the problem in both of the problem cases was due to short delay multi-path. This would be confirmed by the move of my co-workers dad's antenna to another location, thus accomplishing the desired reception of the local and distant signals. We have lots of trees around here, and in both cases, there were trees prosent, and in the Beaumont case, the land next to my friend's house is heavily wooded. I call it the hundred acre woods. So that is what I need to look for before installing antennas.
Thank you so much for pointing me in the right direction. :)

For grins, I was using one of the many on-line tools for calculating the lengths for a LP/Yagi capable of 20db gain for channel 2. :p

The boom length came out to 127 feet. I lost count of the number of directors.

I would like to stack two of those... :D


For grins, I was using one of the many on-line tools for calculating the lengths for a LP/Yagi capable of 20db gain for channel 2. :p

The boom length came out to 127 feet. I lost count of the number of directors.

I would like to stack two of those... :D

You have a station 150 miles away you want to receive? :D

My yard is slightly longer than 127 feet. Let's see...I could top my backyard tree and plant this monster antenna on there. Where to set the guide wires, though, to stop it from becoming a twisted spear of God? :)

You have a station 150 miles away you want to receive?
Probably not. He just wants to annoy the neighbors. :p :p

You have a station 150 miles away you want to receive? :D

My yard is slightly longer than 127 feet. Let's see...I could top my backyard tree and plant this monster antenna on there. Where to set the guide wires, though, to stop it from becoming a twisted spear of God? :)

2 of these at 150ft AGL, would be FANTASTIC!

You could string a net between the two antennas, and catch bats at night. :D

For grins, I was using one of the many on-line tools for calculating the lengths for a LP/Yagi capable of 20db gain for channel 2. :p

The boom length came out to 127 feet. I lost count of the number of directors.

4 antennas with 15 db each would do the same thing and be more manageable.

4 antennas with 15 db each would do the same thing and be more manageable.

Even at 15 dB, that would still be a big antenna. However, such things exist. Here's a 50 MHz antenna with 14 dBd gain on a 69 foot boom.

http://www.m2inc.com/products/6m/6m11jkv.html

Ron

SPECIFICATIONS
Model
6M11JKV

Frequency range 49.9-50.5 MHz
Usuable Frequency Range 49.6 TO 50.75 MHz

Gain over a Dipole 14 dBd
Front to back, Typical >21 dB
Beamwidth degrees E=28° / H=39°
FIRST SIDELOBE -18 dB
STACKING (HORIZ POL) 38' W, 36' H

Feed impedance
50 OHM

VSWR
1.2:1

Input Connector
'N' Female
Balun Half Wave 4:1, supplied
Power Handling
1500 WATTS
Element Type 3/4" Tube W 7/8" Center Sleeve
Boom length and diameter 69' / 2" / 2", 2-1/2" & 3" X 36" CNTR
Wind Area / Survival 10.7 SQ. FT. / 100 MPH
Weight / ShipWt.
83 LBS. / 95 LBS, Truck or air


Heh, heh. And thats only 1 of 4, heh. And thats 14dbd, 16.15 dbi for each one. Figure another 2.5 dbi stacking two, then 5 dbi stacking all four for about 21.15 dbi.

69' long damn!:eek:

69' long damn!
Also at 50mhz, the stacking distance is large too. So maybe figure it needs to be 69 ft high for all four. Then of course it wont work well close to the ground, so youll need a good 100 ft tower to mount it on too, heh.

If youre going to go that insane, you might as well have a 60 meter in diameter parabola dish built, heh.

Also at 50mhz, the stacking distance is large too. So maybe figure it needs to be 69 ft high for all four.

There is an aspect of the problem that is easily overlooked when comparing antenna gains and heights. Antennas on channel 2 interact with the ground to steer the main beam upwards. Tvfool doesn't include that factor in their data. Tvfool does assume that there is more signal when the antenna is raised, but that is based on statistics and not the specifics of a particular antenna's interaction with the ground.

If the ground in front of the antenna is flat and you would like to get the main beam aimed exactly at the transmitter antenna, extra tower height adds significantly. At reasonable antenna heights it's 1 db per each 5' of tower height. If the ground in front of the antenna slopes downward, there is an optimum height where the ground interaction adds approximately 6 db to the gain of the antenna.

Therefore, a single 14 db gain antenna at the optimum height with downward sloping ground in front of the antenna would actually have 20 db gain.

If the ground in front of the antenna slopes downward, there is an optimum height where the ground interaction adds approximately 6 db to the gain of the antenna.

Im out of luck on that, its flat as a pancake around here, heh. I wonder if that guy with the four stacked 69 ft yagis lives in the Texas hill country ?

Ken Nist updated the 8-Bay Modification webpage, testing an alternative feedline
for the CM-4228HD, as well as a 1/4-wavelength balun:
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

Here's some pics (including some rope yagis):

http://www.bigskyspaces.com/w7gj/6mEMEstns.htm

Ron

Im out of luck on that, its flat as a pancake around here, heh. I wonder if that guy with the four stacked 69 ft yagis lives in the Texas hill country ?

This is in Hempstead, TX

http://www.50mhz.org/6m/album02/IMG_0255

Here's some pics (including some rope yagis):

I hate to be under some of those when the wind is blowing strong, jeez. Also I noticed some are mounted near power lines. Nothing like living dangerously, heh.

This is in Hempstead, TX

Hmm, I believe the hill country may start a little to the west of there. I remember driving from New Braunfels ( a little north of San Antonio) to north of Austin at night and I ran into some pretty darn decent hills, heh. I also remember running over an armadillo. (from what Ive been told, I didnt hurt the little critter, heh)

After reading this thread, I'm almost too ashamed to post this, but after finding rabbit ears are insufficient to pick up my one DTV channel (KWWL NBC 7) I am going to attempt to make a folded dipole for this one channel.

Problem is, nobody in town carries 300 ohm twin lead wire, even the local independent radio supply store and Radio Shack.

This will be for indoor use, and I don't have the ability to access the attic antennas (sep. VHF/UHF Yagi) from the room I want to use this in.

Where do you recommend ordering twin lead from? I'll probably also get a new balun and combiner for it also.

It's depressing nobody manufactures a descent indoor VHF-HI antenna considering the demand for one.

Thanks,
Jay

PS - According to my calculations, I'll be cutting it to 31.68 inches long.

Problem is, nobody in town carries 300 ohm twin lead wire, even the local independent radio supply store and Radio Shack.

Make your own from copper wire. Enter your info here at K7MEMs site for the design measurements : http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15313

Lowe's carried twin lead the last I checked.

Problem is, nobody in town carries 300 ohm twin lead wire, even the local independent radio supply store and Radio Shack.

There are Menards stores in Iowa, I think. They carry the super-cheapo super-thin indoor Magnavox-branded stuff for like $2 for 50 feet (so you're not exactly getting grade-A stuff, but for $2....)

For the perfectionists out there, here's a link to some transmit quality 300 ohm twin-lead:

http://www.dxengineering.com/products.asp?ID=170

Ron

Thanks everyone for the wide array of options!

here's a link to some transmit quality 300 ohm twin-lead:

Whew, about 30 cents a ft, but it is strong 18 gauge stuff.

Lowe's carried twin lead the last I checked.
Not my Lowes anymore. What it seems they do when their stock gets low, is put it on clearance for a weekend, and then dont stock it anymore.

I have not stopped in for a while but have an antenna question. I took down a huge wineguard UHF and put up an XG91 (recomended on some web site). I still get CBS with many drop outs. I am at 13081 with the XG91 up about 40'. I have a windgard AP-8275 pre-amp but still get CBS (ch.5.1) only 30% of the time. I assume I will need to add another XG91 along side the one I have?? Several other channels (NBC, ABC, PBS, FOX) are fine but CBS is not.
An email from Ch.5 said they are at full power. (Ch.5 was also my worst analog station)

It's easy to build your own Folded Dipole....or a Yagi:
http://www.wfu.edu/~matthews/misc/dipole.html

Note that as long as the wires are the same size, it doesn't matter
how far they are separated:
http://www.n-lemma.com/calcs/dipole/fdipole.htm
Set "Assumed Dipole Impedance = 75 ohms" in the input fields and desired wire diameter.
FYI Wire sizes: http://en.wikipedia.org/wiki/American_wire_gauge
Then notice the input impedance is always 300 ohms as you vary wire spacing (S).
Although not shown here, bigger wire (or tubing) sizes have wider bandwidth.

So you can wrap your wire of choice (insulated or not) around some sort of rigid object
(e.g. wood, Sked40 PVC pipe, etc). Since Sked40 pipe is mostly air, the velocity factor
correction is negligible, whereas with wood it is not.

Yet another folded dipole calculator:
http://www.k7mem.150m.zzz/Electronic_Notebook/antennas/folded_dipole.html
[Must change *.zzz to *.com due to forum's pesky URL editbot....]

I have not stopped in for a while but have an antenna question. I took down a huge wineguard UHF and put up an XG91 (recomended on some web site). I still get CBS with many drop outs. I am at 13081 with the XG91 up about 40'. I have a windgard AP-8275 pre-amp but still get CBS (ch.5.1) only 30% of the time. I assume I will need to add another XG91 along side the one I have?? Several other channels (NBC, ABC, PBS, FOX) are fine but CBS is not.
An email from Ch.5 said they are at full power. (Ch.5 was also my worst analog station)Are you pointed at CBS (5.1/47)? I presume you are. The 91XG has a very narrow beamwidth (a trade-off for the increased gain) and therefore requires more precise pointing. I use one in what appears to be similar circumstances to yours. I have at best 2 edge reception with many hills and trees. I found that antenna location was very critical. I have UHF signals (39 and 44) that are about 60-75% quality (60 required to lock) but go to less than 30% if I move the antenna up/down as little as 2 ft. I have run the 91XG as high as about 20 feet up but find that these channels do the best in my case at 12 feet. I am 100 feet below Line of sight. I have found a hotspot but if I move left/right as little as 3 or 4 feet or up/down 2 feet the signals go away. My point is with no line of sight to transmitters a hotspot may be where you might least expect it. Unfortunately, hotspots may also change with the seasons.

Not much help but they say misery loves company.

dmatch

For grins, I was using one of the many on-line tools for calculating the lengths for a LP/Yagi capable of 20db gain for channel 2. :pThe boom length came out to 127 feet. I lost count of the number of directors.

Was that for a Log Periodic Dipole Array or a Log Periodic Yagi Array?

Curious because: in a LPDA, the trade off is low SWR across at wide frequency range with moderate gain (e.g. diminishing gain contribution after 3-5 elements), while a LPYA will still provide a low SWR, as well as higher gain.

If you have a link to a LPYA calculator, I would love to have it.

BTW, if gain is the game....it's hard to beat a dish reflector (for 20 dB of gain @ channel 2, the diameter would be quite small compared to a 127' boom).....wider is better than longer :-).

[Must change *.zzz to *.com due to forum's pesky URL editbot....]
What is the deal with that ? Some oddball links are OK, yet K7MEMs site is edited by the bot, heh ?

BTW, if gain is the game....it's hard to beat a dish reflector (for 20 dB of gain @ channel 2, the diameter would be quite small compared to a 127' boom).....wider is better than longer :-).
You neglected to do the math. A 20 dBi dish at 54 MHz would be approx. 80 feet in diameter.

Ron

I am at 13081 with the XG91 up about 40'.

Have you considered another CBS station?

The generic tvfool plot for 13081 shows both WROC and WBNG as stronger than WTVH. What's your plot look like?

I took down a huge wineguard UHF and put up an XG91 (recomended on some web site). I still get CBS with many drop outs. I am at 13081 with the XG91 up about 40'.Is the 91-XG mounted in the same spot the Winegard was? Have you tried fine tuning the height to find a possible sweet spot for UHF 47? Did you tilt the antenna up any? I have found these slight tweaks to be very beneficial for marginal UHF stations. Just as dmatch stated, I have found "lowering" the height 6-12 inches has made quite a difference more than once.

Are you using any kind of VHF antenna?

You neglected to do the math. A 20 dBi dish at 54 MHz would be approx. 80 feet in diameter.

I would go for a little more than that to ensure the 20 dbi gain, maybe around 150 ft in diameter, heh.

I would go for a little more than that to ensure the 20 dbi gain, maybe around 150 ft in diameter, heh.
Here's the calculator I used:

http://my.athenet.net/~multiplx/cgi-bin/parabolic.main.cgi

Ron

You neglected to do the math. A 20 dBi dish at 54 MHz would be approx. 80 feet in diameter. Ron

Actually...for channel 2, the dish diameter would be 54' (assumes a driven element with unity gain and 100% efficiency).

Gain = 10 log (4 pie A/WL^2), where A = area of aperture.

On a parabola, unlike other antenna styles, the aperature area is less than the diameter of the dish, is what Ive read. A good parabola diameter needs to be about 6 to 10 times the wavelength.

Also on aperatures, calculating the aperature area is relatively easy. But finding the aperature SHAPE can be a mystery. On a yagi, the consensus on the shape is that its a horizontal oval. I assume on a parabola, its round. On many other antenna types, its still a mystery as far as I can tell. Knowing the aperature shape is key to getting the right stacking distances, according to the latest stacking theories, ie you stack so that the aperatures shapes just touch each other.

Was that for a Log Periodic Dipole Array or a Log Periodic Yagi Array?

Curious because: in a LPDA, the trade off is low SWR across at wide frequency range with moderate gain (e.g. diminishing gain contribution after 3-5 elements), while a LPYA will still provide a low SWR, as well as higher gain.

If you have a link to a LPYA calculator, I would love to have it.

Antique DOS app: Google logyagi.exe

BTW: Why would anyone build a huge parabolic and not take advantage of gain
in the feed system (e.g. CM parabolic uses 2-Bay Bowtie).

More info re REAL Parabolics:
http://www.digitalhome.ca/forum/showthread.php?t=96216
http://www.digitalhome.ca/forum/showthread.php?t=96113
http://www.rocketroberts.com/cm4251/cm4251.htm
The Lafayette Parabolic used a Yagi feed....
Go to end to see a big C-Band dish re-purposed for UHF band....

The Lafayette Parabolic used a Yagi feed....

Thats the one (pictured in the ad) I used to dx uhf with in the old days. That ad was in the Layfayette catalog probably from about 1968-1970 as I recall paying a little more in 1973. I had to drive all the way to Long Island, New York to get it. RocketRoberts is now into the Hoverman based Super-G 1483 antennas, so I invited him to look over the stuff modeled in the other forum and gets some real gain, heh. Once he gets back from Japan, expect to see him there.

BTW: Why would anyone build a huge parabolic and not take advantage of gain
in the feed system (e.g. CM parabolic uses 2-Bay Bowtie).


But at 54 mhz, the 2 bay bowtie would be pretty huge too. Actually doing this kind of stuff at 54mhz is beyond insanity, heh. You may as well go buy one of those SETI dishes.

Antique DOS app: Google logyagi.exe

BTW: Why would anyone build a huge parabolic and not take advantage of gain in the feed system

Thanks.....found it.

http://sm2yer.dyndns.org/building/6logostar/index.html

Also found a Log-Yagi Array design article (with design equations, curves) that was published in the 12/1976 issue of QST.

However, given the wide frequency range requirement for TV, the LPDA section would be quite sizable (lots of elements) and the addition of a parasitic director and reflector would not be all that useful.

The example in post #9100 was only to illustrate that a 20 dB dish, for channel 2, would have a diameter of of 54' compared to a 127' long LPYA (although smaller, not practical). It did not take into account gain from the feed system or any losses (e.g. feed blockage, dissipative, spillover, phase errors etc.).

that was published in the 12/1876 issue of QST.

Man, thats an old issue, heh. I have a 1901 recipe book that you have to turn the pages very slowly or else they crumble.

You could also probably get 20dbi with a cantenna. Just have to use one of those size coffee cans the buying clubs sell it in, heh heh.

BTW: Why would anyone build a huge parabolic and not take advantage of gain
in the feed system (e.g. CM parabolic uses 2-Bay Bowtie).

You can't use a high gain feed. It won't properly illuminate the reflector.

http://www.qsl.net/n1bwt/chap11.pdf

Ron

Here's the table of contents for the link I posted.

http://www.qsl.net/n1bwt/contents.htm

Ron

Yeah, I dont think the Channel Master 4251 parabola with the 2 bowties had much, if any more gain than if they had used a folded dipole at the focal point. The 2 bowties were away from the actual focal point of the parabola, so that may have hurt it compared to using a folded dipole placed right at the focal point. The reflector behind (in front of) the 2 bowties helped the design a lot, but it would have also helped the folded dipole if it had been used instead.
The bowties did give it a certain "Wow" factor, that differentiated it from the rest and helped its sales.

Anyone care to back up idle speculation with NEC simulations.....

Heh.

Well, Im not going to go and buy a CM4251 on ebay, heh. They seem to be going for a pretty penny and shipping cant be cheap.

I could work out a generic example later though.

I have been thinking of building my own 8 ft parabola for a while. I do have a load of 2 X 3 mesh and a 14 inch bandsaw with extra riser. And I think I could build a pvc frame with heat bending. But unfortunately that all takes time and I got tons of other "need to do now" projects for the spring, ie put new roof on garage, paint garage, rotor tiller the garden and plant what has to be planted when, clean out goldfish pond etc etc etc, heh. Not to mention that I want to build two reflectorless NAROD with NAROD reflector DBGHs.

HAH! I beat you to the tilling and Spring planting. :)

Now to get the reception problems worked out.

What's happening to KCBS after the transition? Right now, antennaweb.org shows KCBS as my strongest station (green antenna required) whereas post June transition, it drops to the BOTTOM of the list (violet antenna required) but has the same distance and heading (well, heading changes from 37deg to 36deg). The broadcast channel also is changing from 60 to 43. Are they dropping their power or something? I'm going to have to upgrade my antenna if this is the case. :-(

HAH! I beat you to the tilling and Spring planting

Well maybe, but only because I was getting the garden ready AND working on my latest Hoverman design at the same time, heh.

http://img16.imageshack.us/img16/2893/dscn0728o.jpg

This my eco-friendly SBGH reflectorless design. My bamboo has been sustainably-managed (its a fight to keep from invading everything, heh), hasn't contributed to biodiversity or habitat loss, hasn't exploited workers who managed and harvested the wood (me), and has positively contributed to the local economy (mine), heh. So, I think it could be certified by the FSC, he he.

Right now, Im only getting one channel thats pointed in my Atlantic City direction. Maybe when I transplant it, Ill aim it towards my Philadelphia stations and see what I get. I connected it to the vee point in the bamboo using foam core 300 ohm twin lead into a 300ohm to 75ohm balun for the portable TV connection.

And.......................as a bonus, you save on a grounding block, heh.

That's a whole new way to look at what's known as "HGTV." :)

Ill post build, err grow plans in the next few weeks. Maybe Rebeccas Garden will pick it up, heh heh.

Actually I should call this my Gungan model, thats what their whole technology was based on, growing their devices in SW episode 1, heh.

My bamboo has been sustainably-managed (its a fight to keep from invading everything, heh)

Like kudzu, huh? :p

(Kudzu TV... now, there's a thought!)

That TV looks a lot like the Coby that my wife has in the kitchen, permanently tuned to the one analog channel that it receives acceptably with its single rabbit ear out here in the boonies. Sometime soon we'll have to experiment again with an indoor antenna and converter box, and see if we can pick up at least one station well enough that we don't have to run another coax from the outdoor antenna that serves our main TV in the living room.

That TV looks a lot like the Coby
That TV is a GPX. I have a Coby like that too, but the Coby didnt come with that nifty 300ohm to 75ohm balun (even though there is a jack for it on the back of the Coby) or the AC and 12 volt adapters. The Coby also doesnt have a RCA video input like this GPX has (even though I havent gotten it to work right yet, heh). Ill make up a good cable for connection to the CECB and see what happens.

Was that for a Log Periodic Dipole Array or a Log Periodic Yagi Array?

Curious because: in a LPDA, the trade off is low SWR across at wide frequency range with moderate gain (e.g. diminishing gain contribution after 3-5 elements), while a LPYA will still provide a low SWR, as well as higher gain.

If you have a link to a LPYA calculator, I would love to have it.

BTW, if gain is the game....it's hard to beat a dish reflector (for 20 dB of gain @ channel 2, the diameter would be quite small compared to a 127' boom).....wider is better than longer :-).

The web page was for a yagi-style, I believe. I will see if I can find my way back to the web page.

EDIT: I cannot seem to find the page again, but I think it was an LPDA, actually. All of the elements were straight, and it had no corner reflectors.

> This my eco-friendly SBGH reflectorless design. My bamboo
> has been sustainably-managed (its a fight to keep from
> invading everything, heh),

Perhaps there is a variety of clumping style bamboo that
weaves back and forth like that? (far less invasive
than the running style)

Does the Professor on Gilligan's Island know about this?

Perhaps there is a variety of clumping style bamboo that
weaves back and forth like that?
Yeah, I really dont know why it does that. Some have that zig zag at the bottom, while another piece right next to it is perfectly straight up and down. :confused:

I saw a tip on a bamboo website that tells you how to grow square bamboo (instead of round). Basically, you put a heavy square tube of appropriate size on it when it spouts up in the spring and it will follow that form. :) Ill think Ill try it when it starts to sprout up soon.

One of Confucius' sayings was "We can live without meat. We can live without rice. But if you take away our bamboo, we will die".

I have a Coby like that too,
Oops, I was wrong. It was another GPX. (Coby, GPX and others are probably all made in the same factory in China anyway, heh) So I have 2 GPXs, and 1 International (made in Korea), heh.

Picture of the backs of them for comparison :

http://img291.imageshack.us/img291/8479/dscn0739.jpg
The left black one is the oldest, circa 1988 or so. The grey middle one is the newest, circa 2004 or so. And the dark gray right one is circa 1997. They all work, and are pretty much equally sensitive. On the black International one, I tried to put an F connector on it, but it doesnt work out too well for some reason, heh.

The GPXs take 10 "C" cells, while the black International one takes 10 "D" cells.

I paid $9 for the middle gray one new at a local department store on sale (bought about 5 of them for gifts, heh). I got the International one at a Goodwill store for $5 and just picked up the circa 1997 one, new and in original box, for $5 at the local flea market. They are excellent TV/AM/FM devices to have along while fishing, heh.

Also found a Log-Yagi Array design article

Heres a picture of a 2 element UHF corner reflector log-yagi growing out of my compost pile, heh.

http://img291.imageshack.us/img291/8271/dscn0737.jpg