12 volt TV for motor home
- Thread starter Jerrygroah
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Lou Schneider
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It's not snow, etc. that gives ATSC problems - it's multipath. At our house in WA, the problem is wind blowing through the trees that surround our property. When the air is still, ATSC reception is perfect. But when there's even a little breeze that makes the branches move back and forth, ATSC becomes useless, pixellating and disappearing (blue screen) for seconds at a time. Meanwhile, the analog picture gets a slight amount of ghosting - not enough to be objectionable, hardly noticeable unless you're looking closely.
Same thing happens if you're in a city near the flight path for an airport - as the airplanes go overhead you'll get some ghosting flutter on the analog signal as it's reflected off of the airplane. That's enough to kill the ATSC signal. Or in a moving vehicle as you get reflections off of passing objects.
Same thing happens if you're in a city near the flight path for an airport - as the airplanes go overhead you'll get some ghosting flutter on the analog signal as it's reflected off of the airplane. That's enough to kill the ATSC signal. Or in a moving vehicle as you get reflections off of passing objects.
carson
Well-known member
Interesting, Lou.
Unexpected (?) consequences; I wonder if the engineers ever looked at that phenomenon yet pressed ahead with that design change.
For every action there is a reaction... seems to be a true adage.
My first TV was in 1952, vacuum tube, mechanical tuner. The only station worth watching (Ch4 Seattle) was 100 miles away, talk about a "snowy" picture, even in the Summer. ;D
carson FL
Unexpected (?) consequences; I wonder if the engineers ever looked at that phenomenon yet pressed ahead with that design change.
For every action there is a reaction... seems to be a true adage.
My first TV was in 1952, vacuum tube, mechanical tuner. The only station worth watching (Ch4 Seattle) was 100 miles away, talk about a "snowy" picture, even in the Summer. ;D
carson FL
Jim Godward
Well-known member
carson said:
Carson,
The phemomena was well known for at least 30 years or so. It has been a problem for Law enforcement and other users of digital radio for at least that long so it was and is no surprise. Digital is great when it works and the pits when it doesn't.
carson
Well-known member
Us hams used to call it the "Picket Fence" effect on VHF and UHF.
Ever stop at a stop light and your FM radio quits? Move a few inches and it will come back. Usually in fringe area reception situations.
carson
Ever stop at a stop light and your FM radio quits? Move a few inches and it will come back. Usually in fringe area reception situations.
carson
Jim Godward
Well-known member
carson said:
Know the problem well. Solved most of the problem here though, most of our repeaters are on mountain tops and have a clear shot of the valley.
Jim - AC7PO
scottydl
Site Team
James Godward said:It has been a problem for Law enforcement and other users of digital radio for at least that long so it was and is no surprise. Digital is great when it works and the pits when it doesn't.
Amen to that. There's no in between, like modern cell phones (the same way newer digital radios work). If the signal gets too weak, you just lose the call. And usually there's little to no warning. Rather than at least hearing *something* through the static on older systems, which would indicate that the signal is getting weak (but still readable).
