ONE P25 Channel Only Randomly Decoding

[PeterGV]

I have a VHF Astro Saber and a VHF XTS-3000, both monitoring several conventional systems.

In comparing their performance, I notice that they're pretty much the same (duh!)... EXCEPT, there's ONE (and only one) IMBE-encoded channel that the XTS-3000 only sporadically receives and that the Astro Saber receives 100% of the time. This is driving me nuts.

While the Astro Saber will decode all transmissions on the channel, I only hear about 60% of these transmissions on the XTS. In other words, the XTS will not decode some transmissions... but will decode others (from the same radio). The Astro Saber will successfully decode every transmission.

The lack of decoding does not appear to be a matter of signal strength. I say this because I can connect the XTS to an external antenna, and have the Astro Saber use its internal antenna (or vice versa) and this doesn't seem to change whether the XTS will decode a particular transmission. The lack of decoding doesn't appear related to scanning delays. I get the same behavior

The XTS decodes other IMBE encoded channels without any problems.

Both radios are programmed identically as far as I can tell -- I did a top-node drag/drop between the two in CPS and verified the parameters are identical.

Besides the model numbers, the differences between the radios are that the Astro Saber is a Model I (basic flashcode), and the XTS is a Model III with a slightly more fancy flashcode (590001-001800-9... includes Digital ID Display and APCO Packet Data).

The channel in question is all P25 encoded, and also transmits P25 data (from MDCs) on the same channel.

I'd appreciate any ideas or help you can provide. I've spent quite a bit of time on this now and need some expert advice at this point,

PeterGV
K1PGV

[Pj]

If all settings are truley identical, I would still check the squelch levels of the channel in question. Beyond that, the radio may just need to be benched checked. I would have suggested swapping antenna's to be sure, but since you mentioned you tried an external antenna, that kinda rules that out.

On the XTS, is that channel set to Digital CSQ? Are ASTRO Talkgroups enabled? Any encyption being used (if so, are both radios keyed the same?)

My vote would be for squelch and bench checks.

[PeterGV]

Thanks very much for the reply.

I've been turning the squelch down a little at a time, and I was wondering if the squelch even does anything for digital-only channels. Think I'll try setting is down to 1 (or whatever is the lowest) and see what that does. Thanks for the idea.

>> On the XTS, is that channel set to Digital CSQ?

The problem happens whether the channel's set to Digital CSQ or to use the (correct) NAC.

>>> Are ASTRO Talkgroups enabled?

No.

>>> Any encyption being used (if so, are both radios keyed the same?)

None.

ONE thought I had after posting... Could the DSP version have an affect? The XTS is DSP version N07.03.20 and the Astro is DSP version N08.03.03.

I should probably get the radio bench tested (and Host/DSP upgraded) in any case...

Thanks, and I'll look forward to any other comments/ideas/suggestions you all may have,

Peter
K1PGV

[jmr061]

Host/DSP is the brains that controls the radio. If a bench check shows the radio is properly tuned I would get it upgraded.

Jason

[PeterGV]

Time to revive this thread from a couple of months back... The radio has come back from being bench tested and aligned. I'm still having strange issues. I'm looking for guidance from those who know more than me. Please??

To review: I have an XTS3000, VHF, Flash 590001-001800-9, with Host 07.07.00 and DSP 07.03.20

This radio appears to work fine, EXCEPT... when monitoring ONE particular full-time P25 channel the radio misses about 40% of the audio transmissions. I know this, because if I can sit another radio right next to it (or attach both radios to the same external antenna) the second radio will receive all the transmissions just fine.

The missed messages are not specific to the unit transmitting. Sometimes the missed messages are from the base, sometimes from a field radio.

When a message is in the process of being "missed", if I press the monitor button, I get silence. I never hear a garbled message, or hear audio starting from the middle of a message.

This happens during scanning or when I'm just sitting monitoring this single channel.

I've "dragged and dropped" the personality and ASTRO System parameters between the two radios, so I *think* the programming is the same.

There's no encryption being used.

The radio's recently been benched and fully aligned by my local MSS.

The problem appears to be with this one radio on this one channel. I haven't notice the radio missing transmissions on any OTHER P25 (or analog) channels. And I do think I would have noticed, but I can't be sure.

The ONLY thing that makes this one channel on which the radio fails unique is that it has a lot of data being transmitted on the same channel as the P25 audio.

Any suggestions about what I should do next? I'm at a loss...

Peter
K1PGV