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Hey folks,


A few details: I live in Salt Lake City, and according to antennaweb I'm 19 miles away from the broadcast towers (which, I believe, are on top of a nearby mountain).


I upgraded from an older monoprice outdoor/indoor antenna to an omnidrectional RCA (amplified) indoor antenna. Upgrading from the monoprice to the RCA gives me consistently better reception except for one channel (Fox). For some reason, that one channel is pretty glitchy. I get OK reception for a while, but then I'll get artifacting and lose the signal for about 10-20 seconds. This happens all the time! I rarely, if ever have this problem with the other channels (excepting the occasional storm, etc).


The broadcast towers for all the stations are in the same location, so it's not a matter of distance or anything. I'd also imagine that Fox would be broadcasting at the same signal strength as the other stations (but I don't have any way to verify that ...)


Any thoughts on why only one channel would have bad reception while the others are all fine?


Thanks!
 

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The spectrum for that one channel has a wavelength different from all other channels, and some of its signal could be bouncing off a reflector that uniquely causes phase cancellation only for that particular frequency at your receiving antenna location. Because it varies periodically, it indicates the reflector is dynamic (in motion) causing the phase cancellation to come and go. (This is actually a huge geometry problem with lots of triangles depicting the direct signal from the station's tower, and the other two sides are paths from a reflecting surface.) In general, the remedy is to move your antenna up/down/left/right to get it out of that blackout zone, except that you may cause cancellations on another station. So, be prepared to look for the sweet spot where your receiving antenna gets great reception from all stations. Usually you only have to go a few inches or feet up/ down.left/right to improve reception. And don't be surprised if lowering the height actually increases strength - which sometimes happens, contrary to what you'd expect. Two caveats, using an omnidirectional antenna greatly increases blackouts due to interference and reflections coming from the wrong direction, especially when used in mountainous terrain. And, at 19 miles from the towers the signal level outdoors should be plentiful, but how much gets indoors depends upon the attenuation from construction materials and other signal blockages.
 

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Discussion Starter #4
Wow, thanks for the responses, guys!


Mikepier - here's my results from tvfool
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d1349fed9fcd163

FYI, I'm only worried about digital channels.


George - that's very interesting. I'll have to play around with the antenna location and see what happens. What types of reflectors might we be talking about here? Cars? People? The antenna is in a location that might get interference from the apartment above ours. I've got the antenna at about 8ft above ground level, and as close to the outside as I can get it (it's right next to the patio).
 

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SLC is an all-UHF city, so VHF isn't a concern


Gorge M.'s explanation is the most probably reason for the problem. I've coined phrase "single-frequency multi-path" to describe it.


His advice to move the antenna is what usually will solve this issue. Otherwise, a more directional antenna may be necessary to reduce those off-axis reflections.
 
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