Best Conditions for OTA reception ??

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bhelms

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Hi, all! This question has been in my mind for some time. Less-than-optimal reception last evening prompted my lazy butt to finally put it out there. My usually rock-solid PBS digital channel was weak, pixelating, audio drops. I'm wondering if the hazy/hot/humid conditions had anything to do with that.

I know what precipitation can do to any signal. But in otherwise clear air, what are "ideal" conditions for best OTA signal strength? I recall as a youth when my dad and I were DXing on a home built shortwave radio, we got the best results on crystal clear cold nights. That was dense air with very low humidity. The H/H/H conditions are just the opposite. So I would expect worse reception then. Is this true? Any difference by frequency? Analog vs. digital?

I hope the braintrust here can help me understand this better, not that I plan to try to do anything about this weather other than jump in the pool...!

TIA and BRgds...
 
Fgsilva

Fgsilva

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Jul 10, 2004
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Vallejo, CA
well, I am not going to add anything in terms of the causes of that but I share similar experience with my PBS station (Sacramento). The darn thing only acts up when it's recording something!!! IN my case I think it's recording it during the day and I normally double check the signal strength at night when it normally shows the intensity between 88-95%. Now, I have heard that the sun may influence the signal strength but I'm not sure on why.

bhelms said:
Hi, all! This question has been in my mind for some time. Less-than-optimal reception last evening prompted my lazy butt to finally put it out there. My usually rock-solid PBS digital channel was weak, pixelating, audio drops. I'm wondering if the hazy/hot/humid conditions had anything to do with that.

I know what precipitation can do to any signal. But in otherwise clear air, what are "ideal" conditions for best OTA signal strength? I recall as a youth when my dad and I were DXing on a home built shortwave radio, we got the best results on crystal clear cold nights. That was dense air with very low humidity. The H/H/H conditions are just the opposite. So I would expect worse reception then. Is this true? Any difference by frequency? Analog vs. digital?

I hope the braintrust here can help me understand this better, not that I plan to try to do anything about this weather other than jump in the pool...!

TIA and BRgds...
 
H

HDTVFanAtic

SatelliteGuys Pro
May 23, 2005
1,973
0
bhelms said:
Hi, all! This question has been in my mind for some time. Less-than-optimal reception last evening prompted my lazy butt to finally put it out there. My usually rock-solid PBS digital channel was weak, pixelating, audio drops. I'm wondering if the hazy/hot/humid conditions had anything to do with that.

I know what precipitation can do to any signal. But in otherwise clear air, what are "ideal" conditions for best OTA signal strength? I recall as a youth when my dad and I were DXing on a home built shortwave radio, we got the best results on crystal clear cold nights. That was dense air with very low humidity. The H/H/H conditions are just the opposite. So I would expect worse reception then. Is this true? Any difference by frequency? Analog vs. digital?

I hope the braintrust here can help me understand this better, not that I plan to try to do anything about this weather other than jump in the pool...!

TIA and BRgds...


For signal such as OTA that don't require direct line of sight to like satellites, Cold is better than Hot. Cold the molecules are less active and packed closer together (think ice) for better conductivity. Hot, the molecules are bouncing all around and very active - thus less conductivity. As they bounce the hit objects producing heat - and releasing more energy instead of carrying it from the transmitter to you antenna.

Temp inversions are bad for reception as well. If you live near big bodies of water the signal has to go over, that is usually bad as well. That is because the water is usually at a different temp than the rest of than solid ground around it (Note the gulf around florida never falls out the 60s (maybe 58-59 degrees) even when the lows can fall well below this. That acts as a big radiator and can cause temperature inversions when you shoot a signal over it. Tampabay and San Francisco are famous for issue. Houston is horrendous as it moves in OFF THE GULF.

Dry is not necessarily better than damp. It's a mixed bag. Wet conducts better. Notice that some of the best skip-DX weather is when there is a storm in the area.

However, with wet, you have more chances for temperature inversions - see above - and that doesn't help long term stability.
 
Jim5506

Jim5506

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Oct 19, 2004
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Lubbock, Texas
Another thing that may cause digital signal pixellation is if you get skip (long distance channel interference) from a distant station on the same frequency.

The conditions you describe may be conducive to skip. There is really NOTHING that can be done if that is the problem.
 
datwell

datwell

Supporting Founder
Supporting Founder
Jul 25, 2004
654
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Falls Church, VA
Our only gripe with the CM4228 is wind - the 4228 is like a sail in wind.
A breezy evening = not-so-hot HD locals from E*.

--Doug
 
K

KML0224

Active SatelliteGuys Member
Sep 13, 2003
22
2
New Britain, CT
Wind seems to affect UHF signals for me, especially with analog channels. Is this because the wind, which is usually stronger at higher levels, is moving the transmitter around?
 
N

NightHawk

SatelliteGuys Pro
Jan 20, 2005
506
0
Atmospheric absorbtion from water vapor (humidity) and oxygen amounts to less than .01 dB in 80 miles at any frequency less than 1 GHz (any UHF frequency). IOW it's not the humidity. Even a hard rain (100 mm/H) will only account for about .002 dB /KM at UHF.

Most of the fading experienced at UHF is due to one or more of the different types of atmosphereic multipaths that can impact UHF.

Additionally, higher temperatures always raise the noise figure and decrease the gain of any outdoor amplifier.
 
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