Too strong of a signal
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-73 dBm, aka "S9", is a pretty strong signal, but it shouldn't be too strong and shouldn't overload the receiver. I run some of my RTL dongles at -50 dBm or higher on strong local signals, and have no issues with them being overloaded.
Your I/Q symbol plot looks pretty good. Here's what a -40 LSM signal looks like in Unitrunker.
Your I/Q symbol plot looks pretty good. Here's what a -40 LSM signal looks like in Unitrunker.
FreqNout
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I see -70 rx on my p25rx rig here with no issues. As mentioned your I/Q looks solid.
SMA attenuator kits and some step attenuators are on the market for less than $50.
Edit: If you want to do a quick test - disconnect your antenna to reduce your signal or try a paper clip as a poor antenna.
SMA attenuator kits and some step attenuators are on the market for less than $50.
Edit: If you want to do a quick test - disconnect your antenna to reduce your signal or try a paper clip as a poor antenna.
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I am within 2.0 miles and line of sight to a 700 P25 II LSM site.
My signal level is -60 to -65 dBm. EVM 2-4%
I get some chop, however it is minimal. My advanced tab settings are all on default.
This has been my issue with P25RXII - the traffic channels RSSI are pretty hot compared to the control channel RSSI, resulting in poor audio. The latest firmware has attenuated the signal somewhat, which results in better voice reproduction. Not sure if that is the best approach to the issue. BTW, I would die for that tight I/Q plot.
With the default settings and gains on auto, the P25RX-II should handle any signal you throw at it. It looks great with +22 dBm from an HP signal generator. It works great parked next to a mega tower. The reason the IQ plot is tighter on the P25RX is that the channel filter is very linear. The small distortion on the P25RX-II because of the insane analog IF filter on the P25RX-II. Some of the distortion caused by the filter is equalized out digitally, but not completely. The benefit is that cell phone towers don't cause issues. The price to be paid is a little bit worse EVM. We'll get it figured out. You shouldn't be having issues with "too strong of a signal".
That plot looks great!
All I can say is that with the current firmware, my indicated signal strength is significantly less than it was before, and markedly less than what is shown by other devices connected to the same antenna system. The result is, wrt to P25RX-II, is better decode of the traffic channel audio: much more intelligible than previous iterations of the fw. Perhaps there is another reason for why there has been an improvement, but nothing has changed on my end.
I'll double check the RSSI readings for accuracy. There may be an offset in the experimental version or something like that. The reason for the improvement in the recent experimental version is changes to the ADC rates, decimation filters, and channel filter. Does your other software display RSSI in dBm? Has it been checked for accuracy with an analyzer?
One shows dBm; another in dBFS, and another in *I'm not sure what units (UT2).* Several receivers running different software that pretty much agree with each other as far as relative signal strength is concerned, and the P25RXII is the outlier currently showing lower power from a site not far away. I'm not complaining because the audio is improved over previous versions; but I'm not sure the actual signal is being represented accurately. But the I/Q in OP25 and UT2 show a fairly tight pattern, and P25RXII less so. It is a simulcast site and there are two other member sites within 4 and 8 miles, so...
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Here is a short video of the P25RX-II monitoring a CC using baudline. The input signal strength is -96 dBm. As you can see the AGC is maintaining the signal peak at -20 dBFS before passing on the samples to the symbol synchronizer / decoder. dBm is decibels relative to a mW. dBFS is a relative measurement that is decibels relative to full-scale.
I'm going to post some baseline non-calibrated data to what I see for reference's sake. The control channel, which indicates -65 dBm in this shot, is variable by +/- 3 or so db. As you can see, pretty strong. This is SDR Console using a RTL device, same antenna system.
The P25RX-II fw 12-20-2147 tuned to the same cch, using the same antenna system as above examples. Previous fw versions indicated a much more powerful signal, in line with the other programs. Indicating -90dBm, varying between -100 and -85 at times. This version indicated a significantly weaker signal than previous fw. All Gains are set to AUTO, Model 5.
Thanks for posting the screen captures. I don't know about the absolute accuracy of the other systems, but I understand that you saw a relative change in the readings from the P25RX-II since the radical changes to the ADC rates, filters, etc. That makes complete sense. I'm in the middle of doing some tests with a signal generator now. You are correct! There is definitely a new issue with signal-strength-indication in the latest experimental versions. I'm on it.
If you would like a similar response to this, try RX Model 1 in the latest. Here is a plot of RX Model1 with an input signal of -93 dBm.
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