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Discussion Starter · #1 ·
I've been experiencing some strange signal drops on UHF 21 and would like some help identifying potential causes. Antenna is a ClearStream 2V pointed in between the two antenna farms in my area about 75 degrees apart. No pre-amp, using Philips LTE/5G filter.

I use the Signals GH iOS app hooked up to a HDHomeRun tuner, which charts signal quality over time. Since I have two tuners, one chart is orange (channel 10 - can be ignored) and white for Channel 21.

First type of signal drop - signal quality has quick drops and recoveries of 20-30% or more for a few minutes, then signal quality issue disappears.
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Second type of drop - signal gradually drops and recovers over time (20-30+ minutes). While not captured, I have seen it go from 98% signal quality, all the way down to the 50s, then back up to 98%
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The first looks like some kind of intermittent RF interference. It could be from electrical or electronic equipment, or a nearby transmitter.

Second type of drop is most likely due to atmospheric conditions, AKA tropo. Signals that are 1-2 edge or more often suffer from signal drops, degradation or interference due to tropo, or lack of it.

It would be nice is a RabbitEars report was posted.
 

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Discussion Starter · #3 ·
Sorry about that. RabbitEars.Info

Any tips on identifying the source of the RF interference? I thought low VHF (and to a lesser extent high VHF) was most susceptible to interference, what's common to cause issues for UHF? There's two nearby low power FM stations on 96.5 and 88.7, but I do have a channel master FM trap in place that pretty much nukes those signals.

Tower is 17.1 miles away, direct line of sight. I am having a hard time understanding what power they are transmitting at. On RabbitEars, I see a special temporary authority for 0.25 kW and a license for 1000 kW. And also a construction permit for 100 kW. Not sure why they would want a STA for 0.25 kW when their license is for 1000 kW.
 

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Interference sources, especially intermittent issues, can be very difficult to find. Common nearby sources can be things like motors, high efficiency lamps or electronics, especially PC computers, or nearby two way radio transmitters. The best way is with a directional signal detector. A portable AM radio tuned to a quiet spot on the dial will sometimes be useful to detect smaller sources in the house or nearby. I agree that UHF is less sensitive to RF interference. To interfere with a 90% signal it's probably fairly powerful or very close.
 

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For locating interfering signals on UHF, I would suggest a cheap SDR dongle and have a listen on RF21. If you hear interfering signals, build or buy a small directional antenna and try to track them down.

I've purchased two of the cheap blue R820T2/RTL2832U ebay dongles and they work fine, but rtl-sdr.com sells a modded dongle that is good-to-go right out of the box, with an SMA connector...
 

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Discussion Starter · #6 ·
For locating interfering signals on UHF, I would suggest a cheap SDR dongle and have a listen on RF21. If you hear interfering signals, build or buy a small directional antenna and try to track them down.

I've purchased two of the cheap blue R820T2/RTL2832U ebay dongles and they work fine, but rtl-sdr.com sells a modded dongle that is good-to-go right out of the box, with an SMA connector...
I already have a cheapie RTL-SDR dongle, hooked up to my TV antenna, usually for running spectrum scans.

Do you mean just hook it up without an antenna and listen/look for interfering signals on RF21? Then if I find something, add a directional antenna? Which software do you recommend?
 

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A few years ago, I used a program called SDRSharp with a RTL2832 SDR dongle for a similar issue. The software is still maintained. It worked well enough but not for the issue I was experiencing. Provided some interference is visible, I'd guess that a laptop and a small directional antenna would work to triangulate the source.
 

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