SDRTrunk SDRTrunk RTL-SDR skipping over P25 transmissions
The sdr dongles have their own gain and ppm settings. Your gain to be to high or too low, and your ppm could be slightly off. Both can cause decoding issues.
Everything is set to auto except the PPM, I have that set to -3.9 as recommended from a YouTube video.
Dongle with control channel:
So i see no signal on your waterfall.....control should be active all the time. What are you using for an antenna ?
I'm confused on what you mean by no signal on my waterfall, did you not look at the second image?? there is a control channel active you can see the waterfall is constant.
If your talking about the signal all the way to the right then its not a good signal to me. If its not showing control channel and showing idle its not decoding the channel at all.
Take the gain off of auto. It is too much. Your want the noise floor to be lower.
This is mine.
Here's a bigger image, it ALWAYS shows CONTROL active. I'm not sure if you understand.
What should I set the gain to? For now I am going to try 296.
Drop it real low. Look at the signal peak and the noise floor. Keep bumping up the gain to where the signal reaches its highest point. The noise floor will also then start to rise at that point. Then just back it off a little.
Also, 3.9 ppm via youtube? I would set the ppm to 0.0 and then turn on auto adjust. It will give you the ppm needed. Then add that value to the ppm box and turn of auto adjust.
Roger that, I've done both and will update you with the results.
So far listening for a week it has definitely decreased the frequency of this happening, but it hasn’t fully diminished the problem.
I'm going to open this thread again looking for any solutions to fix this, over the past couple days it has gotten worse and I'm out of ideas trying to fix this and I'm getting sick of it. I'm open to ANY suggestions.
Try restarting the program or the entire box.
I don't leave my PC always running, so I'm always turning it on and off. Restarting doesn't help.
Describe your setup and resources available on your PC.
I have a high-end PC with 32gb of ram, 4070Ti, and an Intel i7-13700F. I believe this is the Best Buy link to it if I'm missing anything.
chrismol1
P25 TruCking!
- Joined
- Mar 15, 2008
- Messages
- 1,300
Yea, that PPM adjust should have helped, its clear its visibly off in the above screenshots. Just checking, the modulation should be on LSM if it is not. Other thing I suggest throwing anything out there is testing, User Preferences, Source, Tuner and see if changing it may help
Dom are there any cell towers and/or sites very near you? In my experience that can cause a high noise floor and resultant signal quality issues, which can lead to dropouts. This, in practice can be a frustrating problem to diagnose because the level of received interference can vary a lot, depending on how the cell site is working at a given moment.
If cell site interference is the problem you have a few options, including:
1. Move your antenna(s) a few feet around to try to find the “sweet” spot where your Rx works.
2. Install filtering to restrict reception to the band(s) you want and reduce the cell bands
3. Use.a diretional antenna (such as a yagi) pointed at the tower you want to RX (assuming the cell site isn’t along that path.
4. Use a higher quality receiver with a lower noise floor, like an Airspy (in your case a mini has enough bandwidth)
5. Try OP25 (I have decoded trunked systems under very high cell site noise conditions) with an ordinary dongle, where almost nothing else worked
Depending on the location and site I have successfully done all of the above.
If cell site interference is the problem you have a few options, including:
1. Move your antenna(s) a few feet around to try to find the “sweet” spot where your Rx works.
2. Install filtering to restrict reception to the band(s) you want and reduce the cell bands
3. Use.a diretional antenna (such as a yagi) pointed at the tower you want to RX (assuming the cell site isn’t along that path.
4. Use a higher quality receiver with a lower noise floor, like an Airspy (in your case a mini has enough bandwidth)
5. Try OP25 (I have decoded trunked systems under very high cell site noise conditions) with an ordinary dongle, where almost nothing else worked
Depending on the location and site I have successfully done all of the above.
Yeah I just leave the PPM on 0 and turned auto adjust on, haven't touched it.
As far as cell towers, I'm not sure. I made a map showing the closest cell towers to me. Red dots are cell towers, the line is showing my home area to the P25 towers that I'm guessing I would use that are on top of a mountain.
