TRX-1: DSP Settings

[devicelab]

I know this subject has been beaten to death but up until a couple of weeks ago, I've left the Advanced DSP settings to their defaults. In this case, the default is -2, -4 and 64 for the DSP value. For the most part, the settings have worked fine.

I came across this page by accident: GRE/RS/Whistler based DSP ADC/DAC Adjustments - The RadioReference Wiki

Since my TRX-1 is always attached to an external Diamond D3000N (up at 30ft) it has plenty of signal. I also have a NOAA + FM notch filters inline.

My only complaint about the TRX-1 before was that P25 sometimes sounded a little muddy -- certainly not as clear as radios with AMBE+2 codecs. I don't recall if the TRX has that CODEC or not.

I decided to set my TRX-1 to 48, -1db and -5db this time per the wiki chart. It's been a couple of weeks but the P25 clips I've heard definitely sound better.

Here's just one good example: https://www.dropbox.com/s/hbunuqehdtgyhv7/USFS.mp3?raw=1

(Considering this VHF repeater is about 30 miles away LOS... I'd say this is pretty good.)

Here's a default 'muddy' sample: https://www.dropbox.com/s/c9hhsv83aj62qiu/CBPOMAHA36.mp3?raw=1

(From a helo above a large city only a few miles away... also on VHF.)

 

[eyes00only]

I saw somewhere on this forum to use this but no big difference:
-2 ADC
0 DAC
48 DSP

Which exact settings are working for you?

 

[Wackyracer]

location, is the biggest key to what works for YOU, YMMV using others settings.

 

[eyes00only]

location, is the biggest key to what works for YOU, YMMV using others settings.

That is really true with the TRX1. Nothing like the many scanners I've had in about 45 years.

 

[zerosix]

Do the DSP settings only affect p25 or also DMR and NXDN?

 

[Ubbe]

Only P25.

/Ubbe

 

[zerosix]

Only P25.

/Ubbe

Thought so, thanks for confirming!

 

[dem1]

Do the DSP settings only affect p25 or also DMR and NXDN?

DSP level settings will affect all digital modes. I tested this by switching the DAC (Digital-to-Analog Conversion) level from +2db to -10db (its higher and lower limits) while monitoring a very active DMR talkgroup and feeding the TRX-1 headphone jack output to Audacity. The Audacity waveform shows a notable drop in audio level when I made the DAC switch at about the 1-minute mark.



Audacity's sound activation feature was used to eliminate silence between transmissions.

To hear the difference, I made an short audio file by interspersing dispatcher transmissions recorded using +2db DAC with transmissions using -10db DAC. The volume change between each transmission is quite apparent.

TRX-1 DMR sample.mp3

Since the DAC level adjustment occurs after the digital signal has been decoded, it should only affect output volume and not impact the actual decoding process.

 

[devicelab]

Perhaps I'm wrong but the actual question is whether the DSP Setting value would affect only P25. There's no question that the ADC/DAC settings are global...

 

[DeDawg]

Volume changed, but the audio is still horrible and unintelligible.

 

[dem1]

DSP Level Adapt, ADC Gain, and DAC Gain are all listed together under "Advanced DSP Settings" in EZ Scan and the thread had been discussing all three. So I thought it worth clarifying. But technically you are correct - "DSP Level Adapt" is the only true DSP adjustment.

 

[Ubbe]

The ADC dB level are for the audio level feeding the digital decoder and does nothing for the DMR or NXDN decoding process, it only works for P25. The DAC are the audio output volume from the digital decoder and can be set so it equals the analog audio level. The DSP setting are only for the P25 decoding process and does nothing for DMR and NXDN.

/Ubbe