APX digital quickcall tone length

[ffexpCP]

Anyone know tone length requirements for APX radios to decode P25 tones? I don't currently have any units with the digital tone firmware. The CPS help file was no help.

Is it forgiving on length or does it have to be exact? I've experienced unications being picky about length.

 

[GTR8000]

It's pretty forgiving as long as it receives at least half a second of the A tone, it should start alerting immediately upon receiving the B tone. Very similar to a Minitor. Of course the spec is for 1+3, standard QCII timing.

 

[ffexpCP]

Half second? Are you saying at least 500ms or just generalizing? I have a admin that wants to run 400ms/800ms tone lengths. It works on Unications, I'm just trying to see if it will work on APX with the same timing. They're not receptive to change, so I'm looking for evidential support. This is the time to do it as it's not deployed yet.

 

[GTR8000]

I'm speaking anecdotally, not in absolutes. We don't setup any tones less than the standard 1000ms+3000ms, because it's not good practice to do so. 400ms+800ms is cutting it very close, especially that short of an A tone.

You really need to get ahold of an APX with Tone Signaling so you can extensively test those short tones before committing to that scheme.

 

[ffexpCP]

I agree. They say a consultant told them any tone longer will effect grade of service. I get not wanting to waste airtime, but if that increase in tone length will tie up the trunk so much it will be unusable, I think there's bigger issues.

 

[GTR8000]

I could not agree more! Wow, if the difference of 2.8 seconds is going to make or break you, you've got much bigger issues. Is that a TDMA system, or still FDMA? For whatever it's worth, the tones are actually more robust over TDMA vs FDMA, and more tones to choose from (narrower normalization window with TDMA). Make sure they're referencing the APX Tone Signaling FDMA/TDMA charts when coming up with the tone plan so they don't accidentally set both the A and B tones within the same normalization window.

 

[a417]

say a consultant told them any tone longer will effect grade of service.

Time for this consultant to show their work, if it's something they're willing to hang their hat on.