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-   -   Can't get channel KCBS 2.1 No idea why (http://forum.tvfool.com/showthread.php?t=1507)

PhayenK 30-Mar-2011 6:51 AM

Can't get channel KCBS 2.1 No idea why
 
Hi all,

So I just moved to a new location, farther from the city. My TVFool thing is here:
http://www.tvfool.com/?option=com_wr...8d176aa21d05df

My problem is I can't get 2.1 anymore. I used to have a small directional indoor amped Trek that I used to use in an apartment about 10 miles away. I got all the basics except for 7.1 and 9.1, but could just shift my antenna to get those specifics.

Since I now own the condo I'm in I decided to get an outdoor antenna (it was annoying to walk in front of the directional antenna and have the picture cut out). I bought a DB4 antenna and installed it outside on my roof. I took down an old satellite dish that was on the property and replaced it with the antenna. I wired it straight to the TV through the basement, no pre-amp of any kind. I used TVfool to orient my antenna (even though its suppposed to be multi-directional) I had all the channels and tons I've never heard of before. I was super happy. But I tried to watch CBS for the first time last night and it didn't come in. I rescanned and still nothing. Today I reoriented the antenna another 5 degrees in the right direction, but still no CBS.

Is there something I'm doing wrong? Do I need to get a new antenna? My wire run is over 100', but no splits and no amps. I can make it shorter, I just haven't cut the cord. Any advice would be appreciated.

Thanks

John Candle 30-Mar-2011 8:19 AM

Tv Antennas and Reception
 
When some one says they are using the satellite Tv mount then I know there will be trouble because the small dish satellite mounts are mounted at odd angles. Here is how to point Tv antennas , http://www.kyes.com/antenna/pointing/pointing.html , is the antenna pointed up at the sky ? is the antenna pointed down at the ground ? is the antenna cocked at odd angles ? is the roof of the house blocking the front of the antenna ? I suggest a Winegard HD7084P antenna on the roof with a tripod antenna mount or a chimney mount or peak of the roof eave mount. No preamp or any other type or kind amp. The Tv transmissions are all strong.

John Candle 30-Mar-2011 8:39 AM

Tv Antennas and Reception
 
Read and understand this about , Real Digital Tv Channels , Virtual Digital Tv Channels , Analog Tv Channels , http://forum.tvfool.com/showthread.php?t=695

Dave Loudin 30-Mar-2011 12:34 PM

I'n not sure why John is suggesting the all-channel antenna. If you are getting 7, 9, 11, and 13, then you have a fine antenna. The issue is local interference of some sort, very likely reflections that add up in the wrong way for KCBS's frequency. Don't forget that KCBS is actually using a UHF channel per the real channel column in your TVFool report.

A very nice resource that helps explain the physics behind the situation in a way that you can use is this site. You seem to have a clear shot at the towers as far as terrain goes (all the paths are LOS, or line-of-sight.) What the prediction model can't tell is what buildings and trees nearby may be doing.

ADTech 30-Mar-2011 3:51 PM

Quote:

I'n not sure why John is suggesting the all-channel antenna.
Seems to be a pattern with that recommendation regardless of the intent of the requester. The only thing on low-VHF in the Los Angeles area is a Spanish language Franken-FM on channel 6. You can listen to it on any FM receiver in the area.

Quote:

very likely reflections that add up in the wrong way for KCBS's frequency.
Bingo! The current location is in a spot where multi-path is clobbering that one frequency. The solution is always one of the following: 1) Relocate the antenna to a different spot and try again or 2) Select a narrower beamwidth antenna and see if it nulls the offending reflection. Advanced users might try combining another antenna to create a steerable null, but we don't offer such assistance in setting up such a project. Ken Nist's HDTVprimer site offers some examples.

The DB4 is classified as "multi-directional" because it has a modestly wide beamwidth which usually allows for a less than accurate aim to work or which may allow adequate reception from towers that are spaced out rather than from a single direction as is the case with Mt Wilson.

PS. I get this situation at least once a week from callers or emailers. The above advice has been correct in every case for which feedback has been provided.

PhayenK 30-Mar-2011 6:22 PM

Thanks for all the quick responses. It was annoying how I get all the channels on the same path.

As for the mount, I'm just using the satellite dish's location. I had a spare piece of medium gauge steel tubing that I drilled some holes in to mount the antenna. Its mounted at a slight angle, but it looks like its supposed to be a little.

I'll try a different spot and see if that helps.

Thanks everyone!

Dave Loudin 30-Mar-2011 8:09 PM

Quote:

Originally Posted by PhayenK (Post 7337)
Its mounted at a slight angle, but it looks like its supposed to be a little.

No, you usually mount that antenna with the screen perpendicular to ground. The first thing I'd try is changing the tilt angle back to exactly vertical before anything else. You should then try raising/lowering the antenna in place before searching out a new location.

GroundUrMast 30-Mar-2011 8:29 PM

Quote:

Originally Posted by Dave Loudin (Post 7340)
... The first thing I'd try is changing the tilt angle back to exactly vertical before anything else. You should then try raising/lowering the antenna in place before searching out a new location.

@ DL: Agreed.

@ PhayenK: If reusing a satellite dish mount, beware of the OTA antenna being so low that it is aimed into the roof, a source of signal reflections and attenuation.

I would expect the dish mount to be on the south side of the building... you are aiming at stations NNW of you. I can't help but wonder if your roof blocks the line of sight toward Mt Wilson.

John Candle 30-Mar-2011 9:08 PM

Tv Antennas and Reception
 
The reasons that I recommend all channel antennas is that longer elements at the back of the antenna reject multipath at the back of the antenna better then a 7 thru 69 antenna , the longer elements toward the back of the antenna increase forward gain , the longer elements toward the back of the antenna reject multipath at the sides of the antenna better , The longer elements toward the back of the antenna make for tighter forward reception. So Yes it is a reacuring theme and pattern and Yes you will be reading it again and Yes you will read the explaination again.

No static at all 30-Mar-2011 9:45 PM

Quote:

Originally Posted by Dave Loudin (Post 7340)
You should then try raising/lowering the antenna in place before searching out a new location.

I agree as well. Just a few inches can make a world of difference, even with a strong signal. UHF can be very fickle.

ADTech 31-Mar-2011 5:50 PM

Quote:

The reasons that I recommend all channel antennas is that longer elements at the back of the antenna reject multipath at the back of the antenna better then a 7 thru 69 antenna ,
A novel (and possibly original) hypothesis. Fortunately, it is easy to test for validity (or lack thereof).

Select the most comparable 7-69 to the 2-69 antenna suggested from Winegard's lineup since you recommended one of their antennas. Compare the polar plots that are available for channels 7-69 between each model. If your theory is correct, the 2-69 variant of the antenna will exhibit both a narrower forward beam width, higher comparable peak gains, and will simultaneously suppress the side and rear lobes to a greater degree.

If this shows that there is narrower beam width with greater suppression of side and rear lobes in the range of channels 7-69 for the 2-69 antenna as compared to the 7-69 antenna, then your hypothesis has merit. If it doesn't, your theory doesn't hold up.

mtownsend 1-Apr-2011 11:19 PM

The interesting technical discussion deserves its own thread, so those posts have been moved here: http://forum.tvfool.com/showthread.php?t=1519


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