TRX-1: DMR squelch gate open on P25 system?

[kc5igh]

Greetings:

I recently downloaded the RadioReference data for New Mexico's Dept of Public Safety 700 MHz P25 system and noticed something interesting in the TRX-1's display.

In addition to seeing the usual flashing "T" that indicates the radio is receiving the control channel, I'm seeing an intermittent flashing "S" that, according to the manual, means the "Squelch circuit (or gate) is open DMR". Does anyone know what that means?

The signal strength meter appears to momentarily drop all bars but one when the "S" flashes and picks them all up again when it locks back onto the control channel, so I'm guessing that I may be briefly missing transmissions on the system. A closer look at the RadioReference site information in Sentinel revealed that several of the sites were identified as "P25 700" while others were "Auto". I guessed that the radio may have been spending time looking for DMR signals on the "Auto" sites, so I locked them out to see if that made a difference . . . well, it didn't.

The overall performance of the TRX-1 on this system seems very good, so this may be a cosmetic issue, but I'd appreciate anyone's input about what might be going on.

Thanks in advance!

-Johnnie (KC5IGH)

 

[devicelab]

No the flashing S is just referring to open squelch. Check your squelch knob at the top and make sure it's 'in the zone' -- if you're close to a site then set it on the high side. If you're farther away then leave it lower -- but keep it in that zone as printed on the scanner.

This has nothing to do with DMR.

 

[Ubbe]

The S means that the scanner stopped decoding the data but still detects a carrier.

That could happen if it is a simulcast system as TRX scanners have problem to always decode the datasignal due to interference from other sites on the same frequency that a standard FM detector have problems to solve but detectors using I/Q can handle it much better.

/Ubbe

 

[kc5igh]

No the flashing S is just referring to open squelch. Check your squelch knob at the top and make sure it's 'in the zone' -- if you're close to a site then set it on the high side. If you're farther away then leave it lower -- but keep it in that zone as printed on the scanner.

This has nothing to do with DMR.

Thanks, devicelab! I'm back in the "zone"!

 

[kc5igh]

The S means that the scanner stopped decoding the data but still detects a carrier.

That could happen if it is a simulcast system as TRX scanners have problem to always decode the datasignal due to interference from other sites on the same frequency that a standard FM detector have problems to solve but detectors using I/Q can handle it much better.

/Ubbe

Thanks, Ubbe!

 

[mountainrider]

I'm seeing an intermittent flashing "S"

Please specify. The black S in the upper left corner to the left of the signal bars indicates squelch open, and the white S in the black box to the right of the signal bars indicates squelch open on DMR.

 

[kc5igh]

Please specify. The black S in the upper left corner to the left of the signal bars indicates squelch open, and the white S in the black box to the right of the signal bars indicates squelch open on DMR.

Hi, mountainrider.

I was seeing a white S in a black box that, according to the manual, means the squelch is open on DMR. That was a mystery because I was only monitoring a P25 system at the time.

I took devicelab's advice (see the message string above) and turned up the squelch knob, which caused the symbol to disappear.

Still a mystery why a DMR symbol like that would come up on a P25 system . . .

Thanks.