The Official AVS Antenna and Related Hardware Topic! - Page 59

I expect windows allowing for less attenuation in the lower(1st floor) indoor locations in the field tests may have something to do with it.

I'm in a somewhat similar reception situation like you, and also new to HD OTA reception and antennas. The difference here is I'm further way, 30 miles west of the Boston antenna farms but like you using a Silver Sensor.

I was shocked to discover that I could actually receive anything at all from my distance with the SS. But I got virtually every (network) channel that I had interest in with decent lock when I hooked it up to my HR10-250 in mid February.

Over the last two weeks I've noticed problems with losing Fox WFXT and NBC WHDH. PBS along with ABC, CBS, UPN, and WB, are solid in the lower 90's.

My fear is my problem may be related to the coming Spring season and loss of snow cover. I'm prepared to move the SS outside if necessary and even put up an XG91 if needed. Just when I'll need to do this I'm not sure.

Anyone know if the Rat Shack attenuator is 0-10dB or 0-20dB or ???

Edit: nevermind, I found it...

it's:

Attenuation: 0-20 dB
Return Loss:
5-500 MHz: 10 dB Min.
501-1000 MHz: 8 dB Min.

If you aren't too far away and are hoping to use your UHF antenna for VHF, the fol. claims that the Silver Sensor (indoor LPDA) did a "relatively good job" on Ch11, although the max gain was perpendicular to the UHF max gain direction:
http://www.tvtechnology.com/features...features.shtml

There is a Polish Dipol antenna website that provides a gain figure of about 6+ dBi (4 dBp, relative to dipole) for their Model ASP-8A, a typical 4-Bay Bowtie with reflector (no preamp):
http://www.dipol.com.pl/esklep/a0033.htm
[Note that Polish TV channels use 8 MHz spacing, so PolCh6-12 is our Ch7-13 and PolCh21-62 is our Ch14-69.]

Dipol also makes an ASP-8W Version 3 (about 10 Euros) that adds "whiskers", extending the length for some of the elements in a 4-Bay Bowtie in order to improve coverage in VHF band, plus a snap-in preamp module in place of the balun transformer (so the antenna gain numbers now cleverly incude the Preamp gain).
Unfortunately, they don't provide a curve for this improved model.
Go to fol and Click on the pdf catalog for TV Antenna and Channel info:
http://www.dipol.com.pl/e01.htm
and english entry point to website:
http://www.dipol.com.pl/eindex.htm

As you can see, all they did was turn one of the bow-tie elements into a dipole that resonates at a much lower frequency.
And since the VSWR for a wideband UHF antenna is never going to be all that good to begin with....what the heck, perturb away....
So I've got my bailing wire "extenders" ready to go for my CM-4221 when they fire up VHF DTV in our area...

I added the 3041 pre-amp to my attic antenna, and my reception when to pot. I removed the distribution amplifier, and things were very good. But I don't really get any better digital reception than before. I'm about 38 miles from the antennas, and I have a 3018 antenna. So some questions...

1. I may have turned the antenna a bit during installation of the pre-amp. Is there an easy way to adjust the direction based on signal strength? I don't have a field strength meter, but just trying to adjust for analog look or digital bit rate error (reported as pseudo signal strength) seems very unscientific, on top of the fact that none of those displays is in the attic :-|

2. Does the angle of the boom matter much? Should it be level? Tilted down or up?

3. I had to run a length of twin-lead between the antenna and the pre-amp. It is about 3 feet long or so (pre-fab). Is this a problem?

4. Why am I seeing almost no signal with the distribution amp in the circuit? I have the antenna feeding potentially 10 tuners, so I figured the distribution amp would be appropriate. Without it, it seems OK feeding 5 tuners right now, but I worry about further distribution.

5. Should I switch in the FM trap? It was on when I bought it, so I left it, but I don't know if that's a problem or a benefit.

Xesdeeni

1. The signal meter, tuned to the weakest station you get, is probably the best method, short of a dB meter.

2. The angle matters, and how much depends on how directional your antenna is. Generally speaking, they all work about the same +/- a few degrees. If you have a lot of airplanes, pointing down benefits some, and if you're in a valley or shooting over the horizon, pointing up benefits some.

3. There's no reason that this should be a problem, but if you could get the preamp closer, that would be better.

4. Distribution amplifiers usually insert a lot of noise into the picture. They can also overload. (This assumes that you had it wired correctly and the preamplifier was receiving power properly - distribution amps will not pass DC, so if you had the distribution amp between your preamp's indoor and outdoor units, it wouldn't work right.) Generally speaking, you're better off not using one unless you have to.

5. The FM trap blocks FM signals. This is beneficial if you don't want to receive FM signals through your antenna, and your amplifier amplifies VHF signals. FM resides just above Channel 6 on the broadcast spectrum, and if your amplifier tries to amplify that, it will take some of the power that could be used for television broadcasts. Add to this the fact that FM signals can be quite strong, and you've got a couple of good reasons to use the FM trap.

thanks all -- I'll look into getting an attenuator.

I've been reading for almost a week on this board and can't seem to make a decision. I'm in the 70714 zip code and have used antennaweb.org and checkhd.com to check my data. It looks like most of my HD channels are all in one direction. I had a spare RG6 available from the TV to the attic so for kicks I put one of those TV top RCA UHF/VHF amplified antannas in the attic. To my suprise I picked up several HD channels. My Hitachi TV has the built in QAM tuner and I can pick up UPN, WB, ABC, FOX, CBS, NBC, and PBS in HD with my basic cable subscription but I find the OTA channels to have better quality. The OTA's I picked up are 2-1, 9-1, and 25-1 (including their subchannels). These are in the 80's of signal strength.

Now my TV can find the following channels but can not lock in: 17-1, 23-1, 36-1, and 40-1. I've even tried the same antenna on top of the house but I guess I need a real antenna to pick them up. I don't have a problem with an outside mount antenna so what should I get? I really worried about buying the wrong thing and not being able to return it. Should I get an amp with the antenna?

Do I just order the antenna and go to the hardware store and get some piping to mount on the side of the house? I'm currently living in a typical one-story brick home. The neighborhood is pretty much covered with very large oaks in everyones front yard.

It seems I get conflicting info from the two above websites? Does anyone have another website that I can find out about the HD channels in my area?

Thanks for all the help guys!

digiblur - PM your address to me and I will try to help you sort it out. We need to first find out if there are any topograhical problems (you can't move a hill). Could you also send the call letters of the stations you want so I can easily look up their coordinates? If you know your lat/lon you can go to: http://www.2150.com/broadcast/default.asp
But none of the online sites account for topography. That is a killer in my area.

Try pasting this into your web browser. The red lines shown in the antenna pattern point to you. (Well, actually at your post office.)

http://www.2150.com/broadcast/defaul...=Show+Stations

There are instructions on the top of the page and a link to a website to fine the exact lat & lin of your house.

Bob C

What topography? LOL. I live in Louisiana. What does a hill look like? It's all flat here.

I don't feel comfortable with PM'ing an address. If you punch in 70714 in any of the websites I mentioned above or even Mapquest.com you'll be pretty close to my address.

Ron,

Your point is noted and I don't have a paper to offer a rebuttal. I do know that multipath of -30 dB or higher is a concern.

Take a look at page 66 of the document for signal loss & group delay due to VSWR. Group delay expends tap energy too.

Bob

Continuing story...

After playing w/ RS variable attenuator, it doesn't seem easy to attenuate out dropouts and freezes on chn 4 (45) an NBC channel. One thing I've noticed is that the closed captioning is often garbage even when the pic, sound and strenght meter are good. The DO and freezes seem to corespond w/ strength meter droppng. I can't say I've seen it on other stations.

Anybody got a clue about the CC problem? Is it particularly sensitive to MP?

Any good site to look up power of stations? Antennaweb is nice for diretion and distance, but I think relative power might be interesting.
(I will search thread

(edit...hmmm you guys are reading my mind, that 2150 site looks familiar

Thanks
John

I had no idea where 70714 was. Yup, it's flat alright. I used the center of that zip code area and you have 5 stations in the same general direction ranging from 9 miles to 20 miles away. You have one VHF and 4 UHF stations so you might get away with a UHF-only antenna since the VHF station is ch 13. A good place the start is the Channel Master 4221/3021 but for easy returns you can first try the Rat Shack 15-2160. Also get the RS variable attenuator to put just behind your receiver. Your stations are low power except for PBS at 200 kW - may need attenuation. The low power on the others may be a problem if you have lots of trees to go through. It may take a lot of experimentation and patience.

holl_ands ,

The roof is standard asphalt shingles, over 15# roofing felt, over 1/2" plywood. The metal flashing at the edge of the roof is minimal, maybe a 2"x1" angle, just enough to cover the edge of the plywood. (No ice on the gulf coast of Texas.)

Texas attics in general (and mine specifically) have lots of metal foil covered flexible ducts for the AC. In mine, there is also a hot water heater and two combination furnace/AC evaporator/fan units up there. All of these were behind the antennas during testing.

Testing was done with a spectrum analyzer using the Max Hold function. The data was allowed to build for three minutes and then downloaded into Excel on the laptop. I also used Excel to extract the analog channels visual carrier peak value and the level at the middle of the digital channels from the 4001 data points. The extracted data shows up as the data-points on the graph.

As the Scala truly is flat (+/- 0.2 dB) across the UHF band, it was declared the graphs base line when it was outside on the mast. Then, each antenna's performance was compared to the Scala by subtraction. (Subtracting logarithms is really division, hence it gives us the Relative Gain Ratio of the antennas.) So comparing the 4228 to the 4248 is a real comparison of the relative gain between them that was experienced in this one location. The method is not as clean and scientific as I would like but I think that it does show the relative gain of the antennas outside.

In the attic, all bets are off. 1st, there is the consequences of the attic refections punching through the back-side of the antennas, either adding to or subtracting from the signal coming into the front. 2nd, attic placement turns out to be as important as what antenna is purchased to put up there. (see the attachment to this post.)

I've got some more data taken from another attic but I have not had time to extract it. So all I can say at this point is that that attic was more transparent to UHF than mine was. It also had a sizable window, perhaps 3'x6', in the general direction of the antenna farm. We were close to downtown, well into the city, with lots of taller buildings all around.

What started me on this adventure was just plain curiosity. I had heard so many glowing reports about the CM7777 and how much it improved reception, that I just couldn't believe what I was reading. My previous experience with preamps has always been a disappointment. While they may have reduced the amount of 'snow', they always added noise (grain) and intermodualtion products (IM) that I couldn't stand to watch.

I had folks 10 to 15 miles from our transmitter reporting significant improvements in both analog and digital reception. I knew from experience that any preamp should be in serious overload, causing all sorts of IM, killing any chance of watching anything. Particularly in Houston, with 17 TV stations and 34 transmitters filling its front end with RF energy. It was when I tested the antennas in my attic that the proverbial light went off. The reason any preamp works for them is that there is a 20 dB attenuator in front of the preamp called 'The Attic'.

By the way, an indoor study done in the 60's at 3500 locations, where they measured the signal levels right at the owners TV set on ch-31, showed a median of 17.5 dB loss for wood frame and 26.9 dB loss for brick construction .

Bob C

 

testing attic antenna placement.pdf 201.1630859375k . file

I was looking at the CM3021, looks easy to mount on the outside of the house. I picked up RS 15-2160 today along with the adapter to go to RG6, I'll have to go stick it up on top of the house and see what it does. I'm assuming due to the close proximity I don't need an amplifier. I can pick up the VHF one just fine right now with the cheapy rabbit ears with the VHF antennas down without a problem. I'll post my results back.

Is there much of a gain difference in the RS 15-2160 and the CM3021?

Rat Shack doesn't publish their antenna gain. The CM 3021 is definetly a better of the 2 by far. At 20 miles the Rat Shack should do the job especially over flat land. I have a DT41 here at 21 miles with 91xg and even with 25DB front to back ratio I still get it off the back side.

What would you suggest to catch two markets which are separated by 100 degrees as measured from my house ? The major is 16 miles away and the secondary is 35 miles. The first has two VHF-hi channels (8 & 9) and the other has VHF 13.

From what I can see, a join-tenna wouldn't do for the UHF since the channels are scattered between the two markets. I could do this on VHF though.

Another consideration is something small that won't catch much wind during hurricane season. I was all set for an attic install but the recent excellent posts on attic attenuation have given me food for thought.

I've been mulling this over and can only see the SqS with pre-amp given its wide beamwidth. Any other ideas ?

tpalik,

Seperate antennas on seperate feedlines with a A/B switch before receiver(some receivers even have 2 antenna inputs, RCA DTC-100 is one example) to switch between antennas -- Or a single antenna setup with rotor.

The 2 antenna/2 feedline setup is convienient(I do it here for 2 local markets, although I have a rotor on one antenna setup as well), and probably less expensive depending up what antenna(s) you decide to purchase. As for having to make the 2nd coax run, with rotor you'd have to run a rotor control cable anyway, and of course you don't have to wait for the rotor to rotate with 2 seperate antennas you just flip the switch(you can even get a remote controlled A/B switch as RS for about $50) ...

Here are the specs for the RS 15-2160: http://support.radioshack.com/suppor...oc19/19192.htm

Whether they're completely accurate, I don't know. I'd probably go with the 4221 over it as well especially for channels < 40 or certainly if I had any need for high vhf.

I put the 15-2160 up and I wasn't impressed at all. I actually lost more signal than I gained compared to my little amplified rabbit ear antenna in the attic. Actually just the opposite happened of what I expected. On the VHF 13 channel I went from the low 70's to the low 80's. The other 2 UHF channels I went from the low 80's to the low 70's.

I think I'm going to take the 15-2160 down and bring it back to RS and get the CM3021 antenna that everyone is raving about.

It looks like I'm stuck trying to pick up those 1kw signals that FOX and NBC are sending out in my area. I can pick up their analog signals decently so hopefully one day they will crank up the power on the digitals.

Another weird thing is the 200kw signal from PBS is in the 70's but yet the 30kw signal on channel 13 comes in with more power. Makes me believe that PBS isn't running 200kw. I even tried putting the antenna in the attic to determine if it was too much power but the signal dropped just like it was supposed to in the attic.

I'll post my findings on the CM3021 and I get it... thanks guys!

That is probably normal especially if the PBS is a UHF channel. It takes more power the higher the frequecy to achieve the same results. If you located in one of the topp 100 markets the 4 major networks have to be full power by July1 .

I figured that dealing with other RF technology, but I didn't think the ratio was that much with TV.

Do you have a list of the 100 markets?

Go here:http://www.tvradioworld.com/region1/
click on your state, then area, and the DMA rank will be listed at the top right.

how much of a difference is there between a dedicated UHF antenna and a vhf/uhf/fm antenna? is there that much of a gain difference? reading here in this forum it sounds as though the dedicated antenna performs much more efficiently than a combination antenna. i have asked this same question of local dealers here and i get just the opposite. are the sales on combined antennas down so far that they are just trying to sell them to get rid of them?

Hey all,

Disclaimer: I don't work for this company, but I got great service
from them when I ordered stuff from them. Warren Electronics
in the Quad Cities (Moline, IL) has the 8-bay ChannelMaster 4228
UHF antenna on sale for $39.50. Unfortunately, I got mine there
when it was $53.95. Oh well. Go to Google and do a search
on Warren Electronics, then click on their antennas box when
you get to their site.

Hmm...not a bad deal. I was thinking of the 3021 and I might just pick up the 4228 and call it done. After shipping costs Warren has SolidSignal beat by $5, I don't like the FedEx shipping though, might pay the extra $5 to get the UPS shipping from SolidSignal.

The more you narrow the spectrum of frequency you're trying to receive, the better the performance you'll get because the antenna can be designed for that specific frequency or range. This holds true pretty much all the way down to single-channel antennas. The broader the band of reception, the more trade-offs there will have to be in the design. There's just no getting around it.

Separate vhf/uhf sections also allow for independent aiming which is another advantage. The disadvantage obviously is that you have more than one antenna, they must have separation on the mast between them, and they thus take up more space on the mast and make for a longer lever arm if you're using a rotor.

If you need only uhf and high band vhf (7-13) though, you can actually get better performance with overall less windload/weight with separates.

thanks for your response to my question. i guess now i'll go ahead and order the 91XG and see how it works for me. i've read that a well made UHF antenna can pick up high vhf channels. our local CBS affiliate ( WINK) is on channel 11 and when they finally start their HD feeds they were assigned channel 9. is anyone having any problems receiving their VHF channels that use the 91XG, as their only antenna?

i was referring to the 91XG as a XG91 and the price appears to be reasonable including the extra 5 bucks for the 3 day shipping.

So It's spring time again and trees are leafing out. I have done a search on trees but it seemed that there was no definitive answer on leaf interference with OTA signals.
I have a CM4228 w/a 3041 pre-amp, I am some 40 miles from the towers and have just started experiencing some audio drops and pixelating on only one of my OTA channels. The D* RCA DTC 210 says I have 80%- 90%, could this be leaves or should I look elsewhere?
There are several trees leafing out within 15'- 30' of the antenna.
Perhaps I should get out the pruning saw and report back.