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Old 24-Aug-2013, 7:53 PM   #64
Pete Higgins
Pete Higgins's Avatar
Join Date: Apr 2013
Location: California, 58 miles @112 degrees from Mt. Wilson
Posts: 83

I liked your explanation of how uniform daytime heating can produce smaller temperature gradients, limiting how far out a refracted signal travels. I know it happens because I frequently see it but I hadn’t thought it through to that point. Thanks.

Well, I configured my two new amps. for separate inputs & FM trap IN (default) and got outside before it got too hot (only 82 deg. when I finished) to check them. The first one I tried, I lost all the of VHF signals but UHF was fine. I thought I might be experiencing a temporary fade. I pulled it down and tried the second one. VHF & UHF worked great.

Back to the roof to swap them out again & high VHF was gone. I left it in –line and went back up and switched it to “combined”. To my surprise high VHF was restored. Unfortunately, the UHF antenna is my CM-4228 which has been shown to have a fairly good high VHF response. In any case, signal to noise ratio was restored to the same level as with the other two amps. so if I were to guess it was seeing the signal from my Winegard YA1713. Need to explore further to determine if the VHF port is left connected when the amp. is switched to the combined position. Finally, I tried switching back to “separate” and left the switch ~1/16” from the end of its travel. VHF & UHF signals were both restored to the SNR levels I saw with the other two amps. Presumably, this amp has a bad switch. It has enough friction that I think it will hold where I need to set it so I left it there. If it doesn’t hold I think it would be easier to replace the switch with jumpers than to try and send it back. I have a soldering station with a vacuum pump so pulling the switch is easy. I guess I should be happy that only one out of four had a minor problem?
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