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Old 21-Dec-2014, 3:48 PM   #1
l3uddha
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Join Date: Nov 2012
Posts: 8
Question missing channels and many duplicates??

Hello, here is my TV Fool report:
http://www.tvfool.com/?option=com_wr...d2435f83a94440

I have a UHF directional antenna + pre-amp mounted outdoors using chimney straps. The antenna is 25-30 feet above ground level. The antenna is turned to about 32 degrees magnetic north (used a $5 walmart mapping compass), and is the following model (Antennas Direct 42XG): http://www.solidsignal.com/pview.asp?p=42XG

I also have the antenna hooked up to a channel master CM7777 pre-amp: http://www.amazon.com/Channel-Master.../dp/B000GGKOG8 The pre-amp is a carry-over from my last house so I figured I'd hook it up.

The new coax from the pre-amp runs through one old 1-to-1 port grounding block that was already attached to the house. From there the signal runs through old existing coax to the living room to the CM7777 power injector, then a short coax patch cord to the TV.

I'm having two issues with this setup:
A) I would expect to get the numerous channels shown around the main angle of 32 degrees magnetic north, however I'm only receiving virtual channels 25.X (25.1, 25.2, 25.3) and 48.X (48.1, 48.2, 48.3). The other broadcast towers are in very close proximity, but I'm not picking them up for some reason.
B) For every channel received, there are four duplicates of that channel. All of the duplicates have the same virtual channel number, the show is the same and the reception is solid for each. They seem to be identical.

When I unplugged the CM7777 AC power adapter from the outlet (signal still running through CM7777 power injector splitter) and re-scanned, I received only channel 3 (with good signal on 3). I did not receive any of the 25.Xs or 48.Xs. Channel 3 came in on the Samsung TV scanner as "Air" rather than "DTV Air" as channels usually do. Could this channel be the VHF High WDVZ-CA coming from the opposite direction at 214 degrees magnetic? The channel is TV Land, and that's the only info provided.

With the CM7777 power adapter unplugged and the power injector out of the loop (CM7777 mast output running through the grounding block to the TV), I receive only the 25.X channels, with good signal and no duplicates.

Do you have any suggestions on things to try or change? I'm puzzled at the moment. Thanks
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Old 21-Dec-2014, 4:56 PM   #2
timgr
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Are you saying that you leave the CM7777 on the mast without power? That will block all signal from the antenna. If you are seeing anything, it's likely from the cable downstream of the amp acting as a very poor antenna.

With that antenna, you should get something like 8 or 9 real channels and a few more virtual channels for each real channel. I'd get a new commercially made cable and run it directly from the antenna to the TV and see what I got.
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Old 21-Dec-2014, 5:14 PM   #3
ADTech
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Remove the amp completely, it will hopelessly overload in that location. Reset your tuner by scanning with no antenna attached, then reconnect it and rescan.

If necessary, use the 42XG's tilt bracket to boresight the main boom of the antenna toward the peak of Monte Sano. You don't need a compass for Huntsville's stations.

Quote:
That will block all signal from the antenna.
No, it wont block everything, it will turn into an attenuator of around 30 dB.

Your channel 3 is leaking in either from the local cable system or, more likely, from a nearby cable or satellite box's standard def RF modulator output which just happened to be tuned to TV Land (a cable-only channel) at the time you made your test.

Have you verified that the coax you're re-using is totally and completely unused by anything else in the house?
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Last edited by ADTech; 21-Dec-2014 at 5:25 PM.
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Old 21-Dec-2014, 7:49 PM   #4
l3uddha
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Join Date: Nov 2012
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Thank you both for your replies.

No, I haven't traced that cable completely, but I don't think its being combined somewhere along the line. I have separate runs for satellite (inactive) and cable/internet (active) running into the same room that came with the house. When I did the scan previously I unplugged the cable box and left it powered on with the end of the cord next to the TV, so maybe some signal was being picked up.

I removed the CM7777 completely, did a rough bore sighting and reception is more normal. I haven't cross-checked all of the stations but I am receiving much more now and the duplicate channels are gone for the most part. I am receiving duplicates on channel 11 (WTZT, 11.1 through 11.4) with somewhat spotty reception, but this looks to be coming in on VHF high from ~320 degrees. I am picking up Ch 14 (15.1, WHDF) from ~310 degrees with very good reception.


I'm wondering if maybe I could get better results with a 360 degree omni-directional antenna for my area, installed outside at the top of the mast. Something like this: http://www.solidsignal.com/pview.asp...sku=1579830649

Do you think it would be worth the $50 to try out?
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Old 21-Dec-2014, 8:22 PM   #5
ADTech
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Unlikely. Digital signals and omnidirectional antennas don't play well together.

WTZT applied to move to Monte Sano last year but I don't see anything in their FCC file that approved the request. If that station is important to you, add a small high-VHF antenna aimed in the direction of Ardmore.
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Old 22-Dec-2014, 12:35 AM   #6
l3uddha
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Quote:
Originally Posted by ADTech View Post
Unlikely. Digital signals and omnidirectional antennas don't play well together.

WTZT applied to move to Monte Sano last year but I don't see anything in their FCC file that approved the request. If that station is important to you, add a small high-VHF antenna aimed in the direction of Ardmore.
I will do that. thanks again
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