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Old 13-Sep-2010, 7:59 PM   #1
slmoore
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Join Date: Sep 2010
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Help please - not getting 2 channels

Hello. I'm a newbie to this forum (and also to over-the-air HDTV).

Of the major channels I can currently receive the following and they look great:

NBC - 4.1/27
CBS - 9.1/39
FOX - 25.1/24

However I am not getting anything on the following, which are pretty important to us for college football & kids programming:

ABC - 5.1/7
PBS - 13.1/13

It's weird because the channels I am not getting are in the same direction as the channels that I am getting.

I have an antenna in the attic, w/ RG6 coax going to a Tivo Premier by way of a female-to-female adapter in a wiring closet. No splitters at this time, just joining the antenna coax wire to the TV coax wire. I want the flexibility to move it to other parts of the house. The antenna is about 8 years old - I picked it up from Lowes or Home Depot. The antenna is just sitting in the attic, not mounted or anything. I have tried holding it higher by myself w/ my wife watching the TV and still no reception.

Any suggestions would be appreciated.

Pic of the antenna: http://twitpic.com/2o4tx8

TVFool report: http://www.tvfool.com/?option=com_wr...a362e351d0b480
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Old 13-Sep-2010, 9:00 PM   #2
ADTech
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I would expect that your antenna is appropriate (although not ideal) for your local stations.

Several tips:

Verify the antenna is pointed to the north-west.

Get it up off floor, away from the electrical wiring and ducting. A simple 1X2, broomstick, plastic pipe, etc will suffice.

Don't forget to rescan when making adjustments. The receiver will not automatically do that for you when the antenna is changed unless the channel's info is already stored in the tuner.

Run a temporary cable straight from the antenna to the Tivo for testing purposes. Cables do go bad.

Replace the existing balun (matching transformer) on the antenna with a new one that is rated for UHF and VHF. Baluns go bad..
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Old 13-Sep-2010, 9:19 PM   #3
slmoore
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Thanks for your reply. Yes the antenna is pointed northwest. I used the compass on my iphone to confirm the right heading.

I don't mind putting the antenna off the floor of the attic but I tried holding it 5-6 feet off the ground and the reception didn't improve.

I actually have 4 coax cables from wiring closet to the Tivo location and I tried another one there. Although I suppose it could be a problem in the cable from the antenna to the wiring closet.

Didn't know what a balun was until Googling it but it looks like that's the piece where my coax ties into the antenna. That should be easy enough to replace.

Just noticed that all of the channels I am getting are in the UHF range and the two I'm not getting are in the high VHF range (7 & 13).

Thanks again for the reply!
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Old 13-Sep-2010, 11:28 PM   #4
John Candle
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Tv Reception

I recommend putting the antenna on the roof. Having the antenna in the attic will lose 50% of signal. . Radio Shack has a well made Balun/Matching Transformer , Model 15-1140. . If the house has the flat composition type shingles most people use the tripod antenna mount. Also can use eave mount or chimney mount. . Also read and watch the video about the double rescan at http://www.dtv.gov
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Old 14-Sep-2010, 2:24 AM   #5
mtownsend
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Quote:
Originally Posted by slmoore View Post
Just noticed that all of the channels I am getting are in the UHF range and the two I'm not getting are in the high VHF range (7 & 13).
I think you hit the nail right on the head. Your two problem channels are in VHF while all your other channels are on UHF. This is a good indication that there may be something wrong with the VHF pickup of your antenna.

The short elements and "V" shaped reflectors at the front of your antenna are designed to pick up UHF frequencies. That part seems to be working fine.

The very long elements at the back of the antenna are the ones responsible for picking up VHF. Are there any "phasing lines" connected between those VHF elements? They are usually comprised of two stiff wires that criss-cross as they go between each of the antenna element pairs. This connects the elements on alternating sides of the boom. If you find these, make sure that are not electrically shorted to each other (there should be a gap each time they criss-cross).

On some antenna designs, the phasing lines also get connected forward to a place either directly connected to the antenna terminals (where the balun is usually connected) or somewhere close (allowing the signals to couple-in wirelessly).

If the phasing lines are shorted to each other or if they are connected to the wrong places, it might be causing your VHF elements to be "tuned" incorrectly and thus be ineffective at picking up VHF frequencies.
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Old 14-Sep-2010, 3:48 PM   #6
slmoore
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Last night I didn't get home until late, but I did check the phasing lines and they were not touching at any point they crossed. I also replaced the balun. Neither of these fixed the problem.

Stuff I haven't tried yet:

- double-rescan
- run a single new cable from antenna to Tivo to see whether something in the wiring could be causing a problem
- trying a new antenna
- convincing my wife we need to move to a new neighborhood :-)

Thanks for your help everybody. If you have any other suggestions I would still be grateful!
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Old 14-Sep-2010, 4:51 PM   #7
mtownsend
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It seems unlikely that any wiring problem would be affecting your VHF channels but not your UHF channels. Both of your missing channels seem to be quite strong.

A couple of other things you might try:

1) Try rotating the antenna in a few different directions. Since your antenna is indoors, it's hard to say if there are any signal reflections (a.k.a., multipath) that is affecting your signal. Since your antenna appears to be fairly directional, aiming it in different directions might help it pick out one of the "cleaner" signal paths and allow your tuner to lock on to it. I believe the TiVo has an antenna signal meter function that can help you seek out the best antenna position.

2) If that doesn't work, you might want to test a simple set of rabbit ears into your TV. Since your signals are pretty strong, you can probably pick them up with a simple set of set-top rabbit ears with the elements extended. If the rabbit ears work for the VHF channels and the attic antenna does not, then it's a clear sign that something is wrong/broken on the VHF capabilities of the bigger antenna.
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Old 14-Sep-2010, 5:31 PM   #8
Tower Guy
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Location: Delmar, NY
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Quote:
Originally Posted by slmoore View Post
I am not getting anything on the following, which are pretty important to us for college football & kids programming:

ABC - 5.1/7
PBS - 13.1/13
Poor reception of only VHF stations occur for three primary reasons;

1. Incorrect antenna
2. Interference
3. UHF works better than VHF with indoor antennas.

Assuming that you've rescanned properly, your antenna is fine for VHF, so interference must be considered.

Where could interference be coming from?

Strong FM stations
Power Lines
Electronic equipment in your home

It seems that your FM stations arrive from the same antenna farm as the TV stations. That is a good thing. Verify it using FMfool. If any FM stations are 30 db or more stronger than the TV stations, it's worth trying a filter.

To look for bad power lines, tune the AM radio in your car to 530 KHz. If you hear loud buzzing near your house, call the power company to have it fixed.

To rule out your own equipment, turn off every circuit breaker in the house except the one feeding the TV set. Turn off everything but the equipment needed to watch TV. Then do the double rescan. If VHF reception works, turn things back on one at a time until the interference recurs.

If you find that you need to relocate the antenna outdoors to pick up VHF, the homeowners association can't prevent you from installing a TV antenna on your own property.
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Old 15-Sep-2010, 4:25 PM   #9
slmoore
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Update from last night: I tried an old pair of rabbit ears in the living room attached directly to the Tivo and they work great for both VHF & UHF reception. In fact even the UHF signal is stronger, which was surprising to me. I'd rather not have the rabbit ears in the living room (to keep the wife happy) so I'm going to test reception if I hook the rabbit ears in the wiring closet & in the attic. That will make me feel better about knowing where the problem is too (VHF on antenna, attic location, wiring/interference).

I really appreciate everyone helping a stranger! Thank you!
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