P25RX Bug in 2022-02-10 10:45 FW

[turnpike61]

I've been playing with this firmware for some time now, and as good as it is, it's got some quirks that have caused me a lot of troubleshooting, and I am beginning to believe that they are related to the firmware itself.

1. When first started, the P25RX will establish a signal level with this new FW, and in most cases, it's a relatively good signal level assuming I have the right antenna connected. But, if I don't shut down the P25RX before changing the antenna or even reorienting it (if using an indoor whip), the device will drop the signal level by 10-20DB, and will never recover. That means that the receiver gets quite deaf until I restart, at which time the expected signal level returns. Sometimes I don't notice this till a day goes by and not a single call is logged.

2. The device no longer plays nice with mixed VHF/UHF control channels. Here in VA, I monitor my local city/county simulcast system, and Virginia's STARS statewide system. The selective modulation (either simulcast or CQPSK/C4FM is unforgiving. If I choose CQSPSK, I might hear only one system, Simulcast, another, but sometimes neither. I've taken to not using roaming at all, and have settled on a single CC on UHF so that I can hear something.

Maybe other's are not having these problems. I could revert, but this version corrected the sped-up audio and I really don't want to lose that.
FYI for the record.

Looking forward to all the good things coming out of the P25RX-II testing.

 

[goldmyne99]

. But, if I don't shut down the P25RX before changing the antenna or even reorienting it (if using an indoor whip), the device will drop the signal level by 10-20DB, and will never recover. That means that the receiver gets quite deaf until I restart, at which time the expected signal level returns. Sometimes I don't notice this till a day goes by and not a single call is logged.

I have been running my P25RX on 02-10 since it was released. I swap antennas and change freqs often during various tests. I have not seen my P25RX fail to recover after a loss of rf due to antenna change or freq change. I do not recall having to restart.

@turnpike61 perhaps your issue could be firmware or something else. I also never use roaming.

FWIW, I change between strong (-70 dBm) and weaker (-95 dBm) 850 p25p1 systems and weak (-115 dBm) 770 p25p2 systems.

 

[btt]

I want to clarify that you are talking about the P25RX model and NOT the P25RX-II model for other readers. I've been shipping this stable version for the P25RX-II for more than a couple of months now. If it working well on the P25RX-II model. The 2nd issue you mentioned can be a problem with this version. For the P25RX-II, I released a later testing version that allows LSM / CQPSK to be specified per roaming table frequency. The advanced software / firmware that I released yesterday will allow fine-grained configuration per frequency. I do plan on getting the ported to the P25RX model. It is a very large change that allows for mixed-mode scanning. Give me some time to get this done. I'm not sure I understand what you mean about the signal level dropping. The gain is automatic. For weak signals, the gain is set the the default maximum. It will back-off on gain as the signal level increases. I'm not aware of an issue with this.

 

[FreqNout]

Fyi. I also hot swap antennas on my original p25rx rig with no issue here in my area.

 

[turnpike61]

Yes, it is the original P25RX.

I'll see if there is any other data I can gather on the gain issue here. I see others do not have this, but that doesn't make it my imagination. Maybe something local is desensing the receiver and causing it to choose the wrong gain. How long after a gain is chosen does the algorithm rescan the other gain values?

 

[btt]

Yes, it is the original P25RX.

I'll see if there is any other data I can gather on the gain issue here. I see others do not have this, but that doesn't make it my imagination. Maybe something local is desensing the receiver and causing it to choose the wrong gain. How long after a gain is chosen does the algorithm rescan the other gain values?

When you say the signal changes by 10-20 dB after changing antennas, is that when monitoring a constant signal like a control channel or is it the noise floor changes by 10-20 dB? The RF AGC is constantly updating the gains if necessary (milliseconds). For weak signals ( < -90 dBm or so), the gain is always at the maximum setting.

 

[turnpike61]

Constant signal - control channel.

 

[btt]

Constant signal - control channel.

The signal power measurement on the P25RX is a measurement of the power level to the RF connector. If you see a 10-20 dB change in power level for the same control channel when you change antennas (that should be similar for the frequency you are monitoring), the issue is most likely a connector or cable issue. If it is the P25RX only (your other receivers are fine when using the same antennas and connectors), then it could be the RF connector is broken on on the P25RX? If you would like me to take a look, please email and I will let you know where to send it.

 

[FreqNout]

I see others do not have this, but that doesn't make it my imagination.

We are trying to recreate your 'bug'. No one has said it is your imagination. Help us help you. Give us more details on your settings, freqs, so we can try to recreate the issue, unless you are leaning to a hardware fault.

 

[turnpike61]

We are trying to recreate your 'bug'. No one has said it is your imagination. Help us help you. Give us more details on your settings, freqs, so we can try to recreate the issue, unless you are leaning to a hardware fault.

I didn't say anyone said it was my imagination. Maybe I should have phrased that differently. The settings and frequencies are of course completely unique to my location and the system I'm listening to. It may be related to a hardware issue as BTT is saying.

Todd, can I open the unit to inspect the SMA female from the other side? I don't need to send it back if it's just a connection that can be fixed by me.

 

[btt]

Todd, can I open the unit to inspect the SMA female from the other side? I don't need to send it back if it's just a connection that can be fixed by me.

Of course you can! It is a T#15 driver for the screws.

 

[turnpike61]

Hey Todd, opened it up, and found nothing wrong. Actually, the soldering at the SMA connector is top notch. Really first class with nary a flow out of place, and no cracks or cold solder joints. My issue seems to have subsided, so am wondering if I wasn't seeing some odd local interference desensing the control channel.

Cheers.

 

[btt]

Hey Todd, opened it up, and found nothing wrong. Actually, the soldering at the SMA connector is top notch. Really first class with nary a flow out of place, and no cracks or cold solder joints. My issue seems to have subsided, so am wondering if I wasn't seeing some odd local interference desensing the control channel.

Cheers.

It is possibly something like that, but the P25RX does have quite a bit of gain control on the front-end for the AGC (> 60dB, 20dB attenuation) and a very high OIP3 LNA (+47 dBM) . The P25RX (original model) IF filter is an analog, low-IF type (followed by digital filtering and NCO) and while the close-in rejection for the band stop is great, there are some spurious and multiples that can come through. I haven't heard of many issues except for some cell "mega towers" can cause issues when in close proximity. I attempted to resolve this with the P25RX-II utilizing an improved 9-element, band pass filter with >90 dB stop band.