P25RX Tips And Tricks

Changes To The Roaming Mode Of Operation

Starting with version 2021-01-08_1810, the P25RX has improved roaming capabilities. Control channels are tracked dynamically and persistently across frequency changes. It will scan up to 16 control channel frequencies defined in the roaming flash memory. Add all frequencies to be scanned (including the "primary") to the roaming flash. This version uses up-to the first 16 entries defined in the roaming records. If you set the "Switch Control Channel After xx Secs Of Inactivity" to 0, then it will use the control-channel IDLE/BUSY bits to determine if it is time to move to the next channel (this results is much faster scanning). If there is voice activity, then it will remain on the current control channel for the defined talk group timeout (default of 2 seconds).

Scanning NXDN Voice Channels

Starting with version 2021-01-08_1810, the P25RX can be used to scan NXDN-4800 voice channels. Follow these steps to start scanning:

1) Install 2021-01-08_1810 or later firmware.
2) Go to the "Search DB For CC" tab. Delete all rows or "erase roaming flash".
3) Add The NXDN voice frequencies, (not the control channels) in the "CC_FREQ" column. Select these rows and press "add selected frequencies to roaming flash".
4) On the P25RX tab,  enter one of the voice channel frequencies in the frequency box  (doesn't matter which one).
5) Select NXDN for the power-on-mode.
6) Enable Roaming and enter 2 in for the "switch control channel after xx secs of inactivity".
7) Change the Talk Group Timeout to 1 secs
8) press "write config to p25rx".
You should now be scanning your NXDN voice channels!

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

Testing version 2020-10-10_0651 (and possibly later) removed the agc command and replaced it with the agc2 command.
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)

Follow Talk-Group
Use the 'f' command:
$ f
following talkgroup 303 (most recent talk group received)
$ f
un-following talkgroup 303
$ f 347
following talkgroup 347
$ f
un-following talkgroup 347

Talk Group Priorities
By default, the talk group priority for each individual talk group is 1. With a value of 0 or 1 (the priority is disabled), the talk group hold function works normally (defined using the the talk group timeout).

If the talk group priority value is 2 or greater for a talk group, then the priority is enabled for that talk group. When there is an incoming voice grant, this priority value will be compared to the currently active talk group priority. If the talk group in the grant has a higher priority, then it will interrupt the current talk group hold period. When this happens, there is a "TALK GROUP PRI" string added for that record in the talk group log.

 The lowest "enabled" priority is a value of 2. A value of 3 would be higher priority, etc.

Starting The BTConfig Software On The Mac OS X

The easiest way for a Mac user to run the BTConfig program is by downloading the BTConfig.exe file from the download section of website and changing the file extension from .exe to .jar. Once the extension has been changed to .jar, you can double click on the BTConfig.jar file to run the program. Alternatively, the software can be started by running the following command in a console window:  'java -jar BTConfig.exe'