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Old 25-Oct-2015, 11:36 PM   #1
Studebaker839
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Troposheric Propagation?

So I've noticed that whenever it gets to the heat of the day, we have a terrible time with our reception. I have our antenna mounted on the chimney outside. Our reception is perfect every other time of day except when it starts to get hot out. Now that it's starting to cool off, I've noticed it isn't happening like it used to. My father in law said it could be Troposheric Propagation. If so, how do we get around it? Thanks!
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Old 25-Oct-2015, 11:43 PM   #2
Flint Ridge
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Just to help us along here is your old TVFool report. What is your current setup?

http://www.tvfool.com/?option=com_wr...e1c67867644e86

Which channel(s) are you having difficulty with?

Any chance of going higher?
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Old 26-Oct-2015, 2:00 AM   #3
Studebaker839
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My TV fool report is the same. We are roughly 65 miles give or take from the broadcast stations. I'd say the antenna is about 15 ft up or so. We have an antennacraft HBU44 for antenna along with antennacraft 30db adjustable gain amp. It's split four ways, so roughly 100ft total to each outlet. I'm at the top of the chimney so it's as high as I can get it without going a different route as far as mounting a large pole (not a huge fan). Since I'm a novice especially with the tropospheric concept, would adjusting the angle help? Reception is poor for all channels (4, 5, 9, 25) during the afternoon hours.
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Old 27-Oct-2015, 8:46 PM   #4
Studebaker839
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Bump...any thoughts or suggestions?
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Old 28-Oct-2015, 12:21 AM   #5
rabbit73
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Quote:
Now that it's starting to cool off, I've noticed it isn't happening like it used to. My father in law said it could be Troposheric Propagation.
Your father in law might be correct. Tropospheric Propagation and Temperature Inversion are closely related:
https://www.google.com/?gws_rd=ssl#q...ect+tv+signals
Quote:
If so, how do we get around it?
I don't know how to get around it anymore than I know how to stop the rain, but there might be other factors that are affecting your reception.

The first one that I notice is that there is a very strong FM transmitter, KOFM, in Enid that might be overloading your 30 dB preamp. See attachment 1.

Quote:
It's split four ways, so roughly 100ft total to each outlet.
Is the reception any better if you feed just one TV without the splitter?

Are there any trees or other buildings in the signal path?

Is the antenna aimed at 153 degrees magnetic?

There isn't much signal left from Fox by the time it reaches your antenna:



and the curvature of the earth causes the signal to skim the terrain that has been heated by the sun:



1Edge and 2Edge signals aren't as stable as LOS signals.
Attached Images
File Type: jpg Studebaker839TVF FM est.JPG (107.7 KB, 185 views)
File Type: jpg Studebaker839TVFcovKOKH.JPG (115.6 KB, 506 views)
File Type: jpg Studebaker839TVFp2KOKH.JPG (119.5 KB, 469 views)
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Last edited by rabbit73; 28-Oct-2015 at 1:47 AM.
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Old 28-Oct-2015, 11:30 AM   #6
ADTech
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Might be something as mundane as electrical interference from power lines or A/C equipment. You'd really need to hook up a spectrum analyzer and view the signals in order to do anything more than guess. My guess is that it's a combination of factors, neither of which specifically include what is most commonly referred to as tropospheric propagation although the underlying mechanism is closely related.

During the sun-heated hours, the atmosphere's noise level increases from the temperature increase. The increase in the noise floor will eventually swamp out the very weak signals that are just at or above the noise floor of the atmosphere when it's closer to quiescent levels.

The other possible factor is due to the same effect that causes visual mirages. The atmosphere just above the ground, when heated by the sun's energy, can form localized inversion layers that distort the signal path for the incoming signals, causing those signals to refracted or reflected elsewhere than your antenna's location.

Countermeasures for both are the same. A high gain antenna mounted as high as possible away from local noise sources along with a low-noise amp to preserve the system noise figure as seen from the antenna's terminals. That's about as good as it can possibly get.
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Last edited by ADTech; 28-Oct-2015 at 11:36 AM.
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