Using Homepatrol to monitor GATRRS

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BarryC

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I recently purchased a HP-1. Was in Austin recently and tried to monitor GATRRS. GATRRS appeared on screen but nothing heard. Upgraded frimware to V 2.02 and also updated database from RR, still nothing. Is it possible to monitor GATRRS with the HP-1 or better to use a 396T?
 

chikin

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I recently purchased a HP-1. Was in Austin recently and tried to monitor GATRRS. GATRRS appeared on screen but nothing heard. Upgraded frimware to V 2.02 and also updated database from RR, still nothing. Is it possible to monitor GATRRS with the HP-1 or better to use a 396T?
I've owned an HP-1 for about 15 months now and up until about a week ago, it received the GATRRS about as well as can be expected. Now, it's like the HP-1 has gone silent on the system--not deaf (it's still picking up signals as well as it was before), but it just doesn't seem to get very many transmissions from the GATRRS. I'd say I'm hearing maybe about 10-15% of the transmissions I was a week ago. Maybe they're not transmitting, sure, but I find it hard to believe that not one of the APD sectors would have any traffic for half an hour at a time. I've played around with site selection, locking out Simulcast 1 vs. Simulcast 2 and vice versa to no avail.

The weird thing is that I've noticed this a couple of times in the past where for a day or so transmissions were very sporadic. I figured they were having issues with the system and the traffic did return to normal levels the next day or so. The last week though has been really eerily quiet. I know reception on this system is challenging due to the CQPSK vs. C4FM and the slight phase offsets of the simulcast towers and the HP-1 has been the best of the P25-capable scanners I've had, but that just doesn't seem to be the issue here though. Or maybe it is.

Perhaps I should bust out Unitrunker and see if there's anything weird going on with the system...
 

chikin

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Of course, having posted that, I was listening last night around midnight and everything seemed relatively normal. Definitely a lot more traffic than I'd heard in the last few days. Way to make a liar out of me, HP-1.

Site 1 looks normal.
So one thing I did when I was trying to diagnose the quietness was to active the trunk analyzer activity log and look at the lower-level messages from the tower. I found that I would always see the P25 RSB, NSB and IU for nonVU messages almost instantly (I assume the system sends these continuously). This is what led me to believe that the scanner wasn't deaf. But then I'd see very very few GVCG/GVCGU (channel grant/update) messages and the ones I did see looked like the parameters were crazy--lots of high five-digit GADs. I also assume that the messages that are received and logged in the activity log passed their CRC checks so it's not a matter of poor reception corrupting the data. (PLEASE tell me the HP-1 does error correction and trellis decoding on the TPDU packets instead of deinterleaving the data and leaving it at that!) I don't know enough about the P25 messages yet to know if those kind of GADs are normal or not, so I'd have to do more research to be sure. If I ever notice the system in this state again, I'll hook up the 796D and see if it exhibits the same behavior on the system.

As an aside, the HP-1 is frustrating--great hardware with so much promise, marginal firmware. If only I could rewrite it...
 
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