The Official AVS Antenna and Related Hardware Topic! - Page 349

A lot of TVs made from the 1970s to the 1990s did in fact have ferrite sleeves between the tuner and the antenna input terminals. I guess you just have to chalk that up to progress, heh. Ferrite sleeves in quantity are like pennies apiece, maybe less.

Once again, the "theoretical" idea of what an antenna is "supposed" to do has no basis in the real world. Mlmahon, myself, and bigmoose have added that extra boom section to the 91XG, and every one of us has had NOTICEABLE signal improvement.. in my case, the signal was far more stable than the 3 boom unit, and every bit as good as the stacked pair. With the 3 boom xg-91, I had windy day dropouts (not severe, but annoying) on ALL CHANNELS except ONE, were'e talking dropout on 8 channels. After I did the fourth boom section, all 9 channels are rock steady 24/7, no dropout even during severe thunderstorm. I reccommend the fourth boom section to ANYONE, it has worked like a dream for all who have tried it.

OMG, you put 3 additional booms on the XG91 ? Do you have a pic ?

Are we talking apples to apples here or just the addition of 6 directors ?

http://www.solidsignal.com/manuals/9...structions.pdf


If youre only talking about the addition of 6 directors, then I would have to say the stacking distance between the two antennas wasnt correct. (what distance did you use ?) Stacking two identical antennas correctly should get you 2.5 dbi in additional gain (3 dbi theorectical, but not in practice), which is way more than adding 6 more directors can get you.

I only added ONE extra boom section (6 more directors) what I'm saying is that the extra 6 directors gave me just as much reliability as the double stack, they were about equal. And of course, the XG-91 with the extra boom section is much less unsightly, and easier on my rotor motor.

Where can one get ONE boom section for the XG-91? Sounds like exactly what I need.

I was given an old antenna (I believe it is a VHF/UHF/FM antenna, about 10 ft long and the arms expand out to 8 feet, and the arms are U-shaped) that was laying in a field for quite some time. It had a pre-amp that has exposed to the elements, and the connection from the antenna (rusted, and can not move the nuts) to the pre-amp is in bad shape. This antenna is in the attic (about 12 feet off the ground, and there are no windows in the attic), with very little room to move. I have it pointed in the general direction of the stations. I have attached the TV Fool map and I am aiming at the stations in the SE.

Right now I have flat wire stipped and wrapped around parallel wires (???, not really wires but connect the u-shaped arms to each other, and these wires are about 1 inch apart) I have purchased a pre-amp (RCA, not sure of the model number). I have one splitter and the cable run is less than 50 feet. Right now I can not pick up any TV stations (digital or analog).

I have a few questions:

Since the old connections from the antenna are so badly rusted, I was wondering where I can attach either flat wire (2 wire) or Coax to the antenna?

Is the pre-amp required?

Will I even be able to pick up any stations?

I was talking with Rand Johnson at K&L Microwave today, about getting a couple of bandpass filters for 7-13 and 20-51. We'll see how that plays out.

I don't understand why manufacturers are taking so long to designed and produced digital OTA equipment for the Post-Transition configurations (ie. Pre-amps, Amps, Antennas, Filters, etc.). Specifically for VHF-Hi and UHF - limited to channel 51 at the high end.

I took Ken Nists XG91 model, found here : http://www.hdtvprimer.com/ANTENNAS/comparing.html and added 6 more of the exact same X type directors to it. The results :





As you can see comparing the original raw gain chart to this one, adding 6 more directors gives you about .75dbi more in raw gain average. (and no additional gain on the channel 20 end) A lot less than the expected 2.5dbi practical increase from correctly ganging two identical antennas.
I suspect the spacing distance you used was off, producing less gain dead straight ahead and creating more side lobes. Similiar to the "Two Antenna Trick" found here : http://www.hdtvprimer.com/ANTENNAS/ganging.html but not in a good way for you.

Before you ask the next logical question, ie "What is the correct spacing distance for ganging two XG-91s ?", Ill answer it, heh.
That will take a long time, as even with a dual core E5300 at 3.5GHz, the computation time with that model takes about 2.5 hours per 38 channel sweep.

What spacing between the two antennas did you use ? And you did gang horizontally, correct ?

What ?? Do you mean I should go back to experimenting with this kind of crap again, heh. (quite a few directors on the long boom are now missing)



Ive found that once the Law of Marginal Utility is broken, a fine must be paid, heh.

A few photos of the antenna might help.

Where did you find Ken Nist's 91XG (aka XG91) NEC file?
I don't see it in http://www.hdtvprimer.com/SIMS/

Perhaps you can post the unmodified and modified NEC files....

Ill be darned, he took it down. I got mine last July, heh. This is a multi-page-posting one, so let me find a file hosting site.

Okay, heres the original file converted to 4nec2 :

http://www.wuala.com/300ohm/Documents/XG91a.nec

And heres the one with 6 more directors added :

http://www.wuala.com/300ohm/Document...6Directors.nec

See if you can download those OK.

The only place to connect your lead-in cable is to the connection screws and nuts or the active element or elements they are connected to. Anywhere else and you are shorting the ends of your cable together. I guess you have cut loose the old pre, you don't want the antenna double terminated. I would work on those connection screws or the antenna is probably worthless. I couldn't read the image; looks like you are somewhere near Springfield, MO. You can get on a Radio Shack web site and find the approximate range for an antenna with that boom length.

Mattd241,

Welcome aboard!

Enjoy the free OTA HD feeds...

Thanks for the info. I did remove the old pre, and added a new one. I will try and work on the connection screws (the are pretty rusted though). I guess i could try to solder the lead-in cable to the rusted connection and see if that helps.

As a Dish Network customer On Whidbey Island, Wa, I lost access to Channel 4 (ABC) due to a contract dispute between Dish and Fisher Broadcasting. I have a 722 HD DVR with ATSC tuner so I bought and mounted a ClearStream4 Antenna and hooked it up to the Antenna In. When I re-scanned locals, it brought in 30 channels including the Dish banned channel 4. At this point I was starting to think about dumping Dish and going OTA only. Signal strengths measured between 60 and 100 on stations that are as far away as 50 miles, but splitting the signal to feed two other TV's required some amplification so I bought a CM7777 and mounted it on my mast 6' below the antenna.

Weak and strong channels across the UHF band show no improvement in strength I checked the RG6 before installation and found no opens or shorts.

I bought the CM7777 based on the many good reviews on this forum and others. I'd love to get rid of Dish Network, but need to solve this problem first. Any suggestions on where to go first with the CM7777 ?

Great Forum. Thanks in Advance for any help.

Gary

Welcome Garskiff! Nice thorough post! Could you please post your tvfool.com results for your actual location? Information from this report is invaluable for assessing your reception possibilities and situation. Also, how many total feet of cable run do you have in your set up?

Also note that the "signal strength" meters on ATSC tuners do not actually measure signal strength. They're an overall measure of signal quality. Don't expect them to scale with raw signal strength.

Thanks to those who replied to my original message, (02/26/09). To recap, the basic problem is bad digital reception at my relatives house about 60 miles outside of Boston.

I decided to go with the CM 7777, and after receiving it and some other parts, finally got a chance to install it the other weekend. The result was the best analog reception I've ever seen there, but only the top 3 channels, (from the TVFool chart), when I switch to digital. So the question is what next?
After spending some time with the antenna, it looks a lot like a CM 3018. Is there much hope that upgrading the antenna to something like the HD8200 would make much difference? Is it safe to assume that as long as you're making a good connection, the age of the antenna doesn't matter? Post transition, the next two target channels are real 7 and 9, so it can't just be a UHF solution. Are there other tips and tricks I can try?
It's frustrating because the analog picture is now very good. I suspect that if I can't get this to work with a somewhat educated effort, there are a lot of other people who's reception is going to go dark this summer.

Since I posted my last, I had a conversation with "Ron" , a Channel Master tech. support guy, and he mentioned the same thing that jtbell was nice enough to point out about the "signal quality" meter. I've attached my TVfool image that helped me decide on the ClearStream4, and later the CM7777. I was most interested in receiving ABC,NBC,CBS and FOX. The chart is pretty ugly for all but FOX, and it may get uglier after the switch back to VHF in June. I chose the Clearstream4 with that in mind. I had planned on splitting the signal twice with cable runs of about 30' and 50', but I'm not sure that will work without an additional distribution amp.

When I add the splitter into the equation, the signal degrades enough to cause drop outs with a drop in the "quality" indication. It's as if the amp isn't doing anything after I attach the splitter. I didn't terminate the open connection, but thought it would be isolated from the other output.

Thanks y'all,

Gary

Do you notice anything on the analog side with and w/o the pre-amp?

As for your VHF concerns, how do analog 9, 11 & 13 look on the C4? Despite the marketing claims, I would not expect the C4 to do all that well on upper VHF.

If the 7777 wasn't getting power and you were passing signals through it, the signals would be a lot worse. However, make sure that you don't have any splits, etc., between the PIM (power module) and the pre-amp itself.

I'm also concerned about overload. Some of the signals could be too strong for the 7777. Have you tried turning the C4 to other angles to see if it helps?

Your chart is showing levels of stations that would be very difficult to receive where I live. You might try running TVFool with the height set to 75 feet and see if a larger mast or tower would be helpful. Which analog channels now look better VHF, UHF or both? If you don't have too much snow there is hope for the similar digital channels. The CM 3018 looks like a pretty good antenna. That said better UHF antennas can be had but you could keep the 3018 for VHF.
John

You should be able to do that with the CM7777 and no additional distribution amp (which would add more noise). Maybe your CM7777 unit is defective ? It happens.

FWIW, when you do add a splitter the splitter you use should be a power-pass splitter (for example like a Holland GHS-2P) to pass the DC from the CM7777's power injector to only the CM7777 and not to the "other" TV.

Thanks all,

I'm splitting the signal between the TV out on the pwr supply & the TV. I am using a splitter that passes power. The only channels that appear weak are 4 & 5. They are measuring the lowest quality at 60 to 65 before and after adding the CM7777. All other channels including 9, 11 and 13 are 75 to 100 and work great with or without the splitter in the ckt.

I really don't care about the analog stations as I'm setting up based on what I can receive after June 12th. Looks like channel 13 is really using 18 UHF until after June 12th. I'm not getting any indication of problems with too strong a signal on anything I'm receiving. The C4 seems to be doing as well as can be expected given the terrain between the towers and my place on Whidbey Island.

I'm just not sure the CM7777 is working as advertized and am not sure what I can do to avoid returning a perfectly good preamp because I've overlooked something Guess I could swap out RG6, but I don't really think that is the problem. I am using the combined output and FM trap is out. I have peaked the antenna by aiming it at chan 4, 146 Mag. Adjusted using the signal quality meter for max signal. Looks like the 70 deg coverage works fine since I have strong coverage on all the other channels with the exception of 4 & 5.

Thanks all for your help I have 90 days to figure it out.

Gary

Gary,
I find that any time the signal drops below 70 % it causes dropouts on the VIP722. I have some channels that I get fluctuations on. UHF is tough here because of terrain and distance to tower. Sometimes they come in at 40 - 70 %, usually windy, cloudy or rainy weather, etc. and sometimes fluctuates between 70 - 80 % in good weather. As long as signal stays steady above 70 we are okay. Below 70 we get dropouts. Can watch same channels on TV's tuner and no droputs unless signal drops below 40 or so.

Good to know Dave. Thanks! I'm not to the point yet that I want to take down my 50' Panasonic and plug straight into the antenna in, but it's good to know that "at least your sets tuner receives weaker stations, or maybe it's just calibrated different than the 722. I'm sure some of the problem is terrain related, but when it's working steady, I just can't see a difference between having the CM7777 in the ckt and not.... I'd planned to dump Dish when my contract expires in a few months and buy A DTVPal DVR, or an HD TIVO. If I can figure it out. Out here on the left coast the magic number for dropouts seems to be more like 60 or less... I could add a 5' extension on to the 10' mast/chimney mount, but would have to guy it to remain within code. We get some pretty awsome winds where I am located.

Thanks,
Gary

How much cable do you have between the splitter and the antenna/pre-amp?

With ABC, CBS, CW, MyNetwork, NBC, & PBS at 144°M to 146°M and FOX at 170°M, I don't think you can get FOX, while pointing to 145°M. I'm assuming you don't have a rotor.

If you aim the antenna a little towards 133°M, you should be able to get iON, along with everything above (except FOX). You'll get other stations just due to proximity.

For better UHF reception, try to get your antenna above 35' (AGL) and 10' above any structure it's mounted to.

I only have 6' between the splitter and the pwr supply of the CM7777. It's between the pwr supply and the antenna input on my 722 DVR. It's not hooked up to a second TV and is only installed to test the amp. post split. Do I need to terminate the open coax connection with a 75 ohm terminator to the second tv, or is it isolated enough not to make any diff? I do receive ION and 29 other digital channels just fine. The antenna seems to be doing its job with the exception of ABC "Chan 4" post split. FOX has a quality reading of near 100 most of the time with the Clearstream 4 pointed at ~ 145 Mag. Guess I could add that 5' mast extension on just to see if there is a big improvement... It would have to be pretty big to get my wife's seal of approval. It's butt ugly sticking that far above my house ;-)

Gary