APCO-25: AKA P25
I just recently started messing with this protocol. I picked up a Motorola XTS5000, which supports analog usage as well as P25 Phase 1, called Astro25 in the Motorola world. This mode is supported by multiple hardware configurations, Motorola Quantar repeaters as well as PiStar based repeaters and hotspots. I currently have a hotspot and 1 multimode repeater to do my testing with.
My initial observation of P25 operations note that the traffic level is very low. I also am having the following issues, which I am trying to determine if they are normal, or hardware issues:
1) Even when not in use, the first call takes multiple tries to get in.
2) BER is all over the place, from perfect to not great, even with a strong signal (-43dbm)
3) There is often ridiculous packet loss coming back into pistar (80%+), even with excellent internet connections (hardwired 400Mbps)
4) Often I notice it can take up to 3 seconds for pistar to accept the call
5) none of these happen with DMR, D-Star or YSF on the same hardware
Below are observations of the BER and packet loss traffic.
I started with a Motorola XTS5000 which is a handheld UHF radio. My initial impressions and observations are as follows:
1) Software does work well. It is in fact a bit like DMR, but the way things are linked is different.
2) instead of one channel for each talkgroups, it is one channel you change talkgroups used on. Limit of 16 TG per list.
3) you have to assign a personality to each channel, this is where you designate if it's P25 or analog (ASTRO or non-ASTRO). Also, each personality is where you designate the talkgroups list.
4) there isn't much P25 traffic at all, about 1/3 of DMR
5) the XTS portables are heavy, about twice the XPR.
6) I don't like the PTT button feel. It's very soft and shallow with almost no feedback.
7) audio quality is on par with DMR, no real improvement or reason to switch if it were my commercial frequency set.
8) I forgot, we have 2 repeaters down at the moment, leaving me with only 1 repeater, and my hotspots. I can get into both, but P25 seems a bit more finicky than any other mode.
9) its a good backup UHF radio, with what I'm guessing is decent battery life, but I wouldn't run out and get another one.
Update February 9th:
I used a dummy load, power/swr meter with frequency counter, and a TinySA to determine that the frequency stability is adequate, and the P25 wave form appears to be identical to the anticipated. Without sending the radio in for calibration, I can't tell if it is truly off-frequency or needs an alignment.