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When listening to our local repeater, which is now a combined P25/analog machine, every once in a while my squelch opens to a blast of digital noise. I've noticed this problem with at least two different Baofeng radios (a UV-3R+ and a UV-82). I have a receive tone set (146.2) so during a digital QSO I should hear nothing, just see a receive light, which is mostly what happens. But when it breaks through it's not just a momentary annoyance, the squelch stays open for the duration of that transmission - and a QSO which breaks squelch once often does it more than once - so the radio just ends up turned off.

Essentially, we can no longer monitor our local repeater.

Are others having the same problem, and if so, is it with P25 specifically or do other digital modes sometimes break tone squelch on analog radios? Is it related to the tone in use, perhaps a harmonic of the audio frequencies P25 modulates, and if so what tones are safe to use with P25? Is it sloppy tone filtering on the part of our ultra-cheapie analog radios or does it affect "quality" analog radios as well? Is it an odd interaction with the Baofeng squelch tail elimination or some other "feature" of the radio that's on by default, or even just a firmware bug affecting just a few radios? Or is it on the transmit side with somebody's P25 radio transmitting out of spec or somehow configured to send an analog tone on a digital transmission (is that even possible?) and the repeater is passing it through?

Or, am I the only one experiencing this (as indicated by the dearth of results in my googling) and I just need to replace these old non-firmware-upgradeable clunkers?

Thanks, and 73

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  • $\begingroup$ Simple: It has a range of FM tones across the whole audio spectrum often including the PL frequency. $\endgroup$
    – AI7OW
    May 16 at 19:47

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It could be a bug in the repeater controller (it's perfectly possible to transmit digital data with a PL tone), but I'd suspect the Baofengs as your problem. They're not the best radios, and they're priced accordingly. Borrow a better HT (ideally Icom, Yaesu or Kenwood, but Alinco makes pretty good handhelds too although they're harder to find) and see if it does the same thing for you.

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  • $\begingroup$ If it is, as I too suspect, mostly a problem with cheapie HTs, well, anything we can do on the repeater end to fix the problem is good, but nothing will fix the flood of cheapie HTs. ;) However, the pattern when it happens makes me think it's related to who's transmitting, thus I'm hoping it might just be someone with a PL turned on on the digital side and the repeater is passing it through. $\endgroup$
    – MoTLD
    Dec 12, 2017 at 19:07
  • $\begingroup$ Also, determining if it's a cheapie HT problem is mostly why I asked here - there are so many Baofengs out there that if it's a Baofeng problem I expected to see it showing up in my googling, and it didn't. So either it's a glitch in just one generation of Baofeng firmware and it's just affecting a few of us - or it's a widespread problem but the digital noise is just commonly mistaken for static. I fear the latter because we also occasionally hear people responding to a digital transmission with an analog "you're not quite holding the repeater" or the like... $\endgroup$
    – MoTLD
    Dec 12, 2017 at 19:23
  • $\begingroup$ @MoTLD The only way to investigate that possibility (PL turned on for P25) would be to do some experiments of your own. I've not used P25, but if you have such a radio, see if you can enable PL tone and do some tests. Also, try to establish what ham(s) are triggering the problem when transmitting, and check their radio configurations. $\endgroup$
    – Jim MacKenzie VE5EV
    Dec 12, 2017 at 22:01
  • $\begingroup$ @MoTLD re: your followup point, I suspect dual analog/P25 repeaters are uncommon, which might explain the rarity of reports of this problem. The only mode I've commonly seen operate in dual analog/digital mode is C4FM/System Fusion. $\endgroup$
    – Jim MacKenzie VE5EV
    Dec 12, 2017 at 22:02
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    $\begingroup$ @MoTLD We don't have the problem you describe, and we have a lot of cheap HTs in our club. $\endgroup$
    – Lance
    Feb 12, 2018 at 15:23

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