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Author Topic: P25NX - Repeater Linking for the P25 Digital Mode, from the DCC on HamRadioNow  (Read 13497 times)

Posts: 22


« on: November 23, 2016, 05:58:08 AM »

There is life left in P25, perhaps the first somewhat popular digital voice mode on Amateur Radio VHF/UHF. The life comes from a linking system that David Krauss NX4Y introduces at the 2016 ARRL/TAPR Digital Communications Conference. He calls it P25NX - Network Exchange.

The P25 mode started in Public Safety radio in the mid '80's. After about 10 years, those guys say their radios are due for replacement. Hams bought the trade-ins and put them on the ham bands (and eBay). But the repeaters were isolated islands. D-STAR became more popular because were linked, bringing in traffic from around the country or world. P-25 is about to have even more cheap equipment on the market as they migrate to Phase 2, and David's link system could make P25 a competitive mode in ham radio again.

Here's the YouTube link to the complete talk:

Gary Pearce KN4AQ

Posts: 1

« Reply #1 on: April 10, 2017, 09:15:22 AM »

The P25 coalition was created in October of 1989, with the first radios arriving in the early 1990's. Initially Motorola put its money on the VSELP codec, but the P25 steering group chose the DVSI IMBE codec instead, resulting in the Motorola gear having to be upgraded for P25 compatibility.

Major, wide-spread use of P25 didn't begin until the late 1990's and early 2000's.

So it isn't quite as old as you imply.

As far as "life left in P25", you imply this is a bygone standard to a degree, far from the truth. Project 25 Phase II systems are being deployed daily in the United States, the protocol is alive and well in the public safety arena.

Sorry for resurrecting a dead thread, but with the reference to P25NX, I wanted to try and clarify a few things.

Posts: 1

« Reply #2 on: April 17, 2017, 04:40:51 PM »

"As far as "life left in P25", you imply this is a bygone standard to a degree, far from the truth."

I think he may have been implying P-25 in ham radio still has life left.  We all know P-25 in P.S. is here to stay.

There isn't a whole lot of P-25 amateur repeaters compared to the other modes and every time I've tried to make contact on a P-25 amateur repeater, I get no reply, except for once someone tried to respond but couldn't make the repeater.  I run Kenwood P-25 equipment as well as Motorola, and in 10 years of traveling from Pennsylvania to Texas/Oklahoma, and trying P-25 repeaters, still no P-25 ham contact as of yet.  With the P25NX network, might have better luck, but I'm not sure which repeaters have that.  I'll be in Midland, TX in a few days and there is a P25 repeater there, maybe I can finally make a P-25 contact.

Speaking of P25NX, has anyone been able to bring up the website?  I've tried for about 2 weeks now and I can't access the site.


Posts: 29

« Reply #3 on: April 23, 2017, 12:46:09 PM »

Most digital repeaters without a network are dead.  This is mostly Yaesu Fusion (though they may have plenty of FM traffic) machines but there are a few DMR as well.  The Fusion repeaters that are active much of the time are on Wires-X.  P25 has a lot of repeaters given the few hams with the radios to use them.  Much of this is because most are mixed mode like most Fusion machines are.  Adding the network will generate digital traffic.  This might chase off analog users but would get more P25 users on.  I use the DV4mini to make P25 contacts.  I have had a few contacts on local machines but not that many.  I monitor 146.86 (NAC 455) in Arlington, TX for P25 and rarely ever hear anything.  I've also thrown my call out from time to time.  Twice I've been answered. 

The largest problem with P25 for new ham gear is the IMBE vocoder.  It adds hundreds of dollars to each radio equipped with it.  The patent for it has expired.  You can therefore write your own (or download an open source) vocoder to work with it.  However, a manufacturer of radios that has a contract with DVSI for AMBE/+2 like Yaesu, Icom, Kenwood, etc. cannot.  It would violate their contract to do so as DVSI words their license to prohibit doing so.  They must charge the end user a HUGE fee for IMBE because DVSI milks public safety for it.  The patent expired but their vocoder code that's licensed is copyrighted so never in our lifetime.  You need a true open radio platform (SDR is a good opportunity here) that you could load an open source vocoder yourself would make this mode feasible outside of the surplus radios many of us have.  You are never going to find a P25 rig out of the box at HRO. 
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