P25 and AUTO mode

[nanZor]

On my TRX-1 and also a 1040, when setting up for P25, I leave the "RX-Mode" in AUTO.

On weaker signals, I find that -auto- has better decoding than manually tweaking it to FM or FMN. As much as I'd like to tweak, auto is my goto for the Whistlers.

Which makes me wonder about imports from RR and if they leave the rx-mode setting to default of auto, or if they change it. I hand-program for the most part, so I'm not really aware if importing data from RR tweaks this setting, which may not be best for the Whistlers.

 

[Ubbe]

Auto means that it uses the value that are set in the bandplan, either AM, FM or NFM. It should be the same as setting it manually to FM or NFM but I have an ongoing discussion with Whistler about the correct use of NFM mode. As it stands now you might be better off using only FM and not manually setting it to NFM. Unidens support guy suggested that for their scanners FM mode might be better for digital modes even if they actually where NFM channels.

/Ubbe

 

[nanZor]

That is VERY interesting. Yes, on the face of it, AUTO is pretty self explanatory. But many of us regardless of brand, end up manually tweaking to either FM or FMN depending, and it seems possible that AUTO for Whistlers, and FM for Uniden might be better for P25 and each manufacturer's algorithm vs. bandwidth.

Interesting stuff - I'll be watching and hope they get back to you.

I can see the issue being something a manufacturer may want to avoid recommending in order not to introduce any confusion. Glad you brought that up.

 

[Ubbe]

It might be that the narrow filter in the scanner for 12,5KHz channels introduce some distorsion to the high frequency component in the data signal and the wider filter for 25KHz channels have less distorsion, but then you also are more prone to get interference from an adjacent channel.

A narrow channel modulates with a less frequency span and have a lower audio volume from the disciminator that then are sent to the DSP for the digital process. At least the TRX models have a ADC setting of -2dB to +2dB that can be used to compensate for the different levels between 12,5KHz and 25KHz channels but the setting are global and affects all channels. If you think that you do not get optimum decoding of a digital signal then try to change that ADC setting. Using -2, 0 and +2 are sufficient as 1dB steps doesn't make much change to the signal level.

/Ubbe

 

[nanZor]

Yep, that's what I've noticed empirically over the years on the Unidens. And just recently with the Whistlers when the rx-mode is left to the AUTO position for both digital, and for allowing the audio dsp to perform well in regards to analog squelch tails. Which in the Whistler's case, is good since I have less to program when doing it by hand.

I think the general tendency is for those of us who deal with real commercial radios, to naturally want to set the FM/NFM settings to what they should be - yet for scanners we sometimes compromise to get the best performance from consumer-level scanners straying from what is shown in official listings.

 

[dpm3]

I am using a 1080 and have been experiencing somewhat garbled and erratic reception of my local (WA State) P25 Phase 2 system (Tacoma PSRS). I am curious as to whether or not the "Auto" setting might improve my recpetion, but am unable to find an "Auto" setting in the EZ Scan software. Am I missing a setting somewhere or might the "Auto" feture not be available to the 1080 as opposed to the TRX1 & 2 models?

 

[nanZor]

Made me fire up the latest software, even though I normally hand-program...

Ah, it is more easily seen when programming conventional non-trunked P25. I'm still evaluating it.

That being said, I fired up the most recent software, and in trunking sure enough - no option for auto, and it properly defaults to NFM as it should. Still, these are scanners, and not commercial radios, so try the FM option. It *may* help somewhat, even though by most standards, that is the wrong setting. Again, scanners vs real two-way radios.

Worth trying without going totally global with it. Just try it on this system only. If it doesn't help, put it back to what it should be NFM.

Interesting - Talkgroup AGC: I see something interesting - if you have individually checked desired talkgroup agc boxes, but not all of them, if you go into Site Options tab, the dropdown default is still OFF. Makes me wonder if despite seemingly activating agc for a few talkgroups, those settings might not take effect until until the Digital AGC option is set for "Per Talkgroup".

Fun stuff!

 

[Wackyracer]

I am using a 1080 and have been experiencing somewhat garbled and erratic reception of my local (WA State) P25 Phase 2 system (Tacoma PSRS). I am curious as to whether or not the "Auto" setting might improve my recpetion, but am unable to find an "Auto" setting in the EZ Scan software. Am I missing a setting somewhere or might the "Auto" feture not be available to the 1080 as opposed to the TRX1 & 2 models?

Try moving the scanner as little as a inch or turning it sideways can sometimes help.

 

[budevans]

I am using a 1080 and have been experiencing somewhat garbled and erratic reception of my local (WA State) P25 Phase 2 system (Tacoma PSRS). I am curious as to whether or not the "Auto" setting might improve my recpetion, but am unable to find an "Auto" setting in the EZ Scan software. Am I missing a setting somewhere or might the "Auto" feture not be available to the 1080 as opposed to the TRX1 & 2 models?

Tacoma PSRS is a P25 Simulcast Phase II system. Simulcast systems are a collection of towers that act as one. Which means they all send the same traffic. What happens is, if your scanner receives the same signal from multiple towers, the signals arrive at your scanner out of sync. Your scanner processes those out of sync signals which makes it sound garbled. Today there are only two scanners that can reliably receive a Simulcast system. The Uniden SDS 100 and SDS 200.

Bottom line there are no settings in your scanner that can properly decode the (out of sync) Simulcast signals. The only thing that might work with your scanner is to get a directional antenna (yagi). With some trial and error, you point the yagi in various directions to see if you can get a clear signal.

FYI, AGC, FM, NFM and Auto won't have any affect with regards to Simulcast. Regarding the Auto setting, it's only available for Conventional (single) frequency transmissions. It isn't available on P25 Trunk systems.

 

[nanZor]

Bud's exactly right. So, one tries to fudge it on a Whistler with either a directional antenna (to null or peak), using the attenuator in the hopes of knocking down the offending tower in strength, or using a purposely inefficient bullet-antenna and the like. Or a combo of the above. Yeah, PITA.

Also, it's not *supposed* to make a difference switching from the proper NFM to FM, but is worth a *try* when all the variables of consumer-grade scanners and other location dependent variables are involved if it helps decode. Like IF filters that may have a funky slope factor, ripple etc.

Most likely it won't, and certainly wouldn't be a problem on a commercial radio. Like I said, worth a shot even if not the textbook answer, due to scanner tolerances.

 

[dem1]

There's no harm in trying. An earlier thread postulated that local oscillator (LO) drift appeared to diminish P25 reception in Whistler scanners. Under such circumstances in particular, the FM mode's wider IF filter might better pass the slightly mis-tuned P25 signal than the NFM mode.