Follow @bluetail

P25RX Tips And Tricks

 Reference Frequency

The reference frequency is the frequency of the internal reference. This determines frequency accuracy of the frequency synth and the A/D converters. You can use the ref freq value printed on the labels that the device came with or if you are currently monitoring a P25 Control Channel and the device has had some time to warm up, you can use the "Estimated Reference Frequency" shown on the "Signal Insights" page.

Talk-group Auto-Flash

By default, the configuration software has two options "auto flash" and "auto disable encrypted" in the talk-group editor tab enabled.  As new talk groups start coming in, the "auto flash" will write each new talk group to the P25RX flash memory.  As it is writing to flash, there is a brief interruption to the voice audio output.  If you have a system with many talk groups,  you might find it preferable to disable the "auto flash" in the beginning and just manually write the entire list of newly discovered talk groups when you are ready using the "Write Talk Groups" button.  This will prevent the audio from being interrupted every time a new talk group is added to the list.  Once you have a near complete list, you can re-enable the option so that any new talk groups that come in get captured to flash automatically.

List Alternate / Adjacent Control Channels

$ ls altcc     (list the 'learned' alternate channels)

P25 Alt Control Channels
SYS bee00-34a, PRIMARY 859.962500, ADJACENT 858.987500, Site 2, RFSS 1
SYS bee00-34a, PRIMARY 859.962500, ALTERNATE 859.937500, Site 1, RFSS 1
SYS bee00-34a, PRIMARY 859.962500, ALTERNATE 858.962500, Site 1, RFSS 1
SYS bee00-34a, PRIMARY 859.962500, PRIMARY 859.962500, Site 1, RFSS 1
SYS bee00-34a, PRIMARY 859.962500, ALTERNATE 858.937500, Site 1, RFSS 1

$ <space>  (hitting space stops scrolling display, hit return to resume)


Reset Configuration To Default Values

If you decided to experiment changing various things with console commands and used the 'save' to write non-default values to the flash memory,  you can always reset to factory values with the

$ factory

command in the console.  This will reset configuration to default values and reset the device.

Troubleshooting - BTConfig will not start in Windows

This isn't happening for most people.  If this happens on your system, this is very likely due to Windows Defender blocking the application.  It is reported that Windows Defender may not even warn you that this is happening.  You may have to start the software manually on the command line in order to see the reponse from Windows Defender.  At this point, you will be able to verify that the application is ok for Windows to open.


Bluetooth Enable With The Button
If you leave the Bluetooth disabled in the P25RX Configuration tab, you can still enable the Bluetooth module without having to use the configuration software.  A double-click press of the TG button will always enable the Bluetooth module and start the pairing process.  After the pairing process times out, the module will attempt to connect to previously paired devices.

Decode ACARS transmissions Over AM Narrow Band
(available starting with firmware version 2020-07-26_1320)
$ is_control 0  (this will turn off trunking mode)
$ rssi 0 (this will stop the scrolling text)
$ acars 1  (enable AM demodulation and the ACARS decoder)
$ freq 131.55  (tune to a frequency with ACARS transmissions)
$ squelch -130  (set the squelch in dBm)
Then monitor the decoded messages on the Console tab.
Note:  You will probably need a good VHF (130 MHz) antenna for good performance (reception for hundreds of miles).  Audio output is enabled for the line-out and Bluetooth.  This can also be used to monitor other AM narrowband output. Use the freq command to change the frequency.
Temporary Manual RF Gain Adjustment (will be reset to automatic on power cycle)  -starting with version 2020-09-18_0929
$ rfgain 0
invalid rf gain. setting agc to automatic.

RF Gains:
0 to enable automatic gain control
-1,8,14,20,23,26,29,32,35,38,41,44,47 dB
Over-ride Talk Group Timeout Feature  - starting with version 2020-09-20_0844
$ pri_always 1   (enable talk group timeout over-ride,  default 0)
When set to 1, the talk group timeout will be ignored.  On grants with multiple talk groups, the talk group with the higher priority will be used.
Bluetooth Audio Gain
It is best to set this value as high as possible without distortion in order to maintain maximum dynamic range over the Bluetooth wireless link.
$ bt_gain gain_value  (gain_value range is 0.01 to 4.0, default 1.5)
$ save
AGC (audio leveler) command
agc max_gain compressor_thresh rate

max_gain - max gain to be applied to original P25 signal audio levels.
compressor_thresh - the 16-bit audio level threshold that compression will start at.
rate - how fast the gain will change toward the optimal target level.
default: agc 3.5 12000.0 0.05
----
Testing version 2020-10-10_0651 (and possibly later) removed the agc command and replaced it with the agc2 command.
usage:
agc2  target_level   rate
target_level range 0.1 to 1.0  (audio level for agc to target.  default is 0.7)
rate  (the rate that audio levels are adjusted toward the target)