APCO 25 Ham Systems

[myspacebarisbroken]

Question: is a P25 repeater absolutely necessary for P25 amateur radio use, or could one get by using an analog repeater beings that the repeater simply needs to repeat the P25 signal?

[MikeOxlong]

No, analog repeaters will not pass a p25 signal.

You need a p25 repeater or a couple of mobiles specially modded to pass the p25 signal.

[n7maq-1]

Originally Posted by myspacebarisbroken

Question: is a P25 repeater absolutely necessary for P25 amateur radio use, or could one get by using an analog repeater beings that the repeater simply needs to repeat the P25 signal?

It can be done (like TPG Tim's Maxtrac setup on Batlabs) if the repeater will pass flat audio. The only thing is there is no FEC, so what goes in is what comes out. Thew first repeater I used with P25 was a Micor that was set up that way. It would pass P25, or DSTAR, or anything else that broke the squelch as the RX has to be in CSQ mode.

Jim

[myspacebarisbroken]

Hey, thanks Jim!
That's what I figured. Although P25 is a digital signal, it still uses FM modulation, as does analog and beings that programs such as DSD can decode the data by using the audio, I figured that simply passing the signal along would also work.

How well would you say the analog repeater worked with P25 as opposed to a true P25 repeater?

Hey Mike,when you said I would need P25 radios to pass the P25 signal, do you mean for full P25 data? I am only interested in passing along P25 voice.

[MikeOxlong]

What exactly are your plans?

You do realize that you just cannot take a regular analog repeater and expect it to pass p25 without some surgery?

You can't just dial up an analog repeater on your p25 radios in digital mode and expect to communicate

You'll either need a proper p25 repeater such as a Quantar or some way of passing flat audio between a receiver and a transmitter for it to work.

[myspacebarisbroken]

I am interested in getting my HAM ticket sometime in the near future and thought it might be cool to play around with P25 voice.

[sledude]

Originally Posted by MikeOxlong

The 147.2850Mhz repeater in Edgar, Ontario (near Barrie) is now linked digitally with the 444.450Mhz machine in Toronto.

There's also a standalone dual mode repeater in Berkely, Ontario (south of Owen Sound) on 145.2900Mhz.

The 146.610 p25 machine will be soon be linked to the 444.450 p25 in Toronto, NAC 293, 103.5hz

[amham]

I have an Icom R2500 receiver with a P25 board. I'm trying to get this to work on receive for local northern NJ repeaters. I've entered the basic receive freq., and NAC. Do I need to enter an analog/digital PL for receive or other info? Obviously I'm clueless here...any help would be appreciated.

Thks

[ef_basham]

Icom's dstar format, as last I heard it on air, was about as garbled as the present day county shreriff apco25 format. In an hour of listening to the sheriff there was constant chatter about "hang on let me get to a good radio place - I could not hear the last dispatch - you were 10-1 please 10-9" Over and Over again. I'll explain why below--

I believe that system has a voting receiver on it and that may be partially to blame for the problem - it was designed for analog and moved to digital on a whim when money was available and interoperability was the buzzword of the day due to earthquakes and fires. Right now it's only digital modulation... sad.

APCO 25 has good value for amateur comms. First, today's apco25 is simply digital modulation - works OK on narrowband, but with 25 khz channels, there is enough dataspace to put two simultaneous talkpaths into one 25khz channel digitally. So while the morning commute buzzes out over the repeater, two hams could ringdown each other for a private qso w/o bothering the morning commute. Further subdivisions are possible on future revisions of apco25 for text messaging, telemetry, gps, basically short, small, bursty data that can be encoded while voice is running on 1 or 2 talkpaths over one frequency allowing 3 uses simultaneously.

I am not aware of any local apco systems using this - however apco does bring with it 2 special NAC codes - they both have lots of 1's - I forgot the actual code numbers - perhaps someone can post them - but they are like NACs FF7 and FF0 - one is an allcall nac for mutual aid (the purpose of apco25 in the first place) and the second was for some other purpose - I forgot the actual use - perhaps mobile ht to police cruiser/fire truck comms repeated out at high power and digitally re-synced, or store and forwarded comms.

As for repeaters - THE MOST IDEAL configuration is two apco radios back to back decoding nac's do turn on the repeater transmitter, however, I have run digital comms through two true DC coupled FM RF decks (no phase modulation) that I alligned with an 8920 radio test set to ensure that 1khz deviation in made 1 khz deviation out, so there was no distortion. These had to be GOOD rf decks, and at that cost you might as well buy apco mobiles, but the NAC from the mobile units would pass through csq or selected pl's that did not bother the nac being passed through (some interefered some did not) and it would make a digital repeater. It's still best practice to use two apco25 mobiles to make a true digital deck since the signal is regenerated and interferance is eliminated in the deck. 2 back to back FM DC coupled decks have the issue that all high frequency hiss comes on through.

Our sheriff's apco25 system is based on an old fm dc coupled voting receiver for the land they are covering - the voting system sends the NAC back to the tranceiver/repeater half (just one tx antenna) which blankets the valley in RF on their output freq. In one hour I counted 10 instances of units calling for 10-1 10-9 repeats from thieir dispatcher - in fact the better trained units knew when the radio was screwed up and how to move it to get a good signal in a hot spot. They would be better served with analog but perhaps they feel secure with digital.

There is alot of QRM locally here - basically too many mom&pop radio shops who are not professional RF engineers are assembling frankenstien systems not realizing what they are doing. A good example was Hewlett-Packard, who had a hangar next to the numbers on the SJC runway approach. They used a 938 mhz trunked system and had to install inside building bi-directional repeaters to yagi's on the roof pointed to their repeater which was installed by the same company with poorly tuned BPFs and notch filters. They used no circulators on the in building bi-dir amped systems to get the signal out.

What their xyzzy radio shop did not realize is that without a circulator, the SUM and DIFFERNCE frequencies are generated in the 1st IF stage, leaked back out the antenna, and they were re-radiating the SUM of the 938 mhz trunked system and the local high power 107 mhz FM wideband broadcast transmitter nearby to create a 1045 mhz broadband signal which interefered with mode-c transponders on aircraft, as well as IFF military systems. SJC airport reported this to the fcc, the fcc sent 1 of 7 engineers (real engineers) out to investigate as all DX altitutde reports were arriving wrong on radar, and the FCC forced HP to shut off ALL of their inbuilding bi-directional amped systems which made their trunked system useless without them due to the improperly tuned bpf's on the front end by the mom&pop radio shop that set them up for failure.

Digital has a place in modern radio - it cuts static and everything above 3800 hz pretty much. It will do amazing things if you treat it right with the propper support equipment, tuned properly. Everyone sounds the same as everyone else on digital. Since APCO 25 is a public standard it really deserves to be included in ALL mfgrs' rigs as we migrate to digital. It's simple modulation is trivial these days, although mom&pop stores don't even know what an eye diagram is. Let's hope they stay far away from digital systems, as a reminder is on the air right now - all 10-1 and 10-9 over and over.

Properly installed and configured with 2 units back to back a good apco25 setup could be made, and since bearcat 996xt scanners can receive it, it is TRULY a non-proprietary (READ: ENCRYPTED) standard, allowing the general public to tune apco25 ham repeaters on digital scanners. Yes, I am biased towards a-25 - mainly because I support a-25 systems done right, and learn from other's mistakes of a-25 done worng. A few ham cluubs have repeater maintainers with the equipment to properly view the emission spectra and tune the master oscillator or install gps based oscillators on the h/w. Digital isn't for billy-joe and bobby-sue ham yet due to complexity. I would like to see the day when the morning commute can happen, my radio is silent, but if someone wanted to call me they could ringdown my HT and use talkpath #2 to communicate over the same system in different time slots. That day will come. Pressure alinco, icom, and yaesu to make apco25 repeaters and radios for the ham community, and make them interoperable. In a few years it could be as common as DPL on ham radios - which was taboo at first due to the word "digital" in ham repeaters. Fortunately the FCC got a clue and caught up with the times. The FCC is the other half of the problem - it's split into two parts, engineers and bureaucrats. Guess which half knows what they are doing to our spectrum!

[ka5lqj]

Hi!

Ok, I don't know one blame thing about digital on the ham bands. I have to think the voice is FM. Now it seems to me that those formats that are "FREE" without any restrictions would want to be done on hf as well a 2, & 70cm. Digital ssb modes: PSK-64, BPSK, and J-65 would leave some area to be QRMed while P-25 would be totally noiseless. That could be used in long distance disaster communications. If I understand right, the "NET Control" station could type in a code and block pest
and profaners out of the system, LOL!! While I would hope that no one did that, the reality can be found on 75 and 40 meters.

If the cost of setting one of these systems up was to prohibitive, then FM, horizontal-polarization could be used. Home stations would have 4 separate quads, each pointing to a different compass point wit a Halo antenna for general reception. Mobiles could be set up on 70cm with halo antennas to report in to the Home station and if necessary, be sent out to the various home stations a long distance off.

Ponder this and get back to me, LOL!

GOD BLESS,
73,

Don/KA5LQJ

[ef_basham]

73's Don.

Yep - I did verify it with an HP audio spectrum analyzer - dc to 20,000 hz and apco has a pretty hard bpf betweeen 400 and 3000 hz, with most repeaters passing 250-4000 hz (-3dB). it sounds muddy as a result.

It also sounds like UDP data packets instead of tcp/ip - UDP packets are sent on a wing and a prayer that the receiver gets them. Drop one along the way, or the checksum fails, and its warble-warp for a few words.

Adjust you antenna for s/n ratio and suddenly its speech alright, but nowhere near toll quality speach

In my quest to go digital I discovered after one of our last earthquakes that the phone lines were out for a few minutes after a sudden jolt. Everyone picked up the receiver at the same time to dial gradma and see if she felt it up there wherever there is.

The one thing that DID NOT go down was the network. I have 24 MBPS downstream and 3MBPS upstream on fiber from at&t and I'm 225 feet from the fiber hub that services my area (2 houses)

So I started playing search on my android google-play store.

There is a program called LOUDTALKS out there that lets you setup a free account, works on pcs and iphones and androids - anything that can connect to tcp/ip. On a pc that runs 24/7 its pretty nice as it runs in the background.

Basically loudtalks emulates nextel/iden but it uses a codec more like a 56kbps toll quality sampler from the phone company. The result is loud and clear audio sent over the data network, be it wireless or wired.

Best part is you can define your users you want to talk to privately, and even define one to many talk channels. The speach is encrypted over tcp/ip, but it has an analog interface where if you have a network link at 64 kbps or more you can tie in a repeater to loudtalks using an old laptop with mic / earphone jacks.

One thing they do not have is a 1004 hz 0 db tone for allignment but those are easy to come by from agilent.

If you want to have a qso on your phone my loudtalks ID is efbasham. You need to setup your phone with the software which is free, then you need to email me here on this thread with YOUR name on loudtalks. Once I add you to my friends list you are able to call me.

Loudtalks uses very little battery (.1%) - it runs when the phone is asleep and a datapacket arrives - but the best part is you can lock it into using tcp/ip mode. Unlike UDP where dropped packets get ignored, tcp/ip allows 8 packets in the buffer between 2 computers. If packet 5 arrives, then packet 7, a retransmit of packet 6 is initiated. Once it reaches 7, the numbers roll over to 00 again. This makes it a high availability system but may have delays in the speach while requesting a retransmit.

That 56K voice codec sure sounds like a wideband FM station compared to apco 25's little tiny channel bandwidth. I'd encourage hams to get their callsign or name on loudtalks for pc or smartphone - the best part is you can do pc to smartphone calls with it and control who you speak to (and I've already setup a county wide emergency channel with doctors, outside county people who will are hams and will come online if we break off and head for catalina island, as well as carpenders and such who monitor the emergency channel. Sorta like our own private 911. And thats how it is meant to be used - not a party line. You can make as many channels as you want - for chewing the fat on the way to work define a party line, just dont use the emergency net - its there for a reason.

[BigEd1314]

Flat Top, WV (outside of Beckley, WV in Raleigh County)

Mixed mode Analog and P-25

146.850 (-) pl. 88.5 hz

NAC - 293

[HECT]

Northern New Jersey, Hopatcong Area N2VUG/R (Exit 28 Route 80 Area)
Recently Installed Quantar Analog/Digital P25 UHF Ham Band Repeater
Output=448.925 InPut=443.925 PL=141.3 NAC 293
Very Quiet Operation, No Courtesy Tone and short hang time.
Most Users are configured for MixedMode operation Analog/Digital P25
If users are in Digital Mode, we will hear you if you ID in Analog Mode, and usually switch Modes

Echo Link is provided by: N1IRL Please connect and join anytime.
Echo Link in in Analog Mode for now as users Transection to Digital P25
If users are in Digital Mode they will hear you and switch to Analog Mode

[EMT911]

Add Midland Texas: 147.82/147.22 NAC 093 to your list.

P25 is allowed in amateur service. Remember, digital modulation is NOT encryption, it is a modulation type. D-STAR is not really ICOM developed, it was developed by the Japan Amateur Radio Group and pushed by ICOM thus leading to the assumption ICOM developed it. It uses AMBE. IDAS is ICOM and is not compatible with D-STAR as IDAS uses AMBE-2 format. Hope this mindless rant clears some of this up.

[nickcarr]

Originally Posted by HECT

Northern New Jersey, Hopatcong Area N2VUG/R (Exit 28 Route 80 Area)
Recently Installed Quantar Analog/Digital P25 UHF Ham Band Repeater
Output=448.925 InPut=443.925 PL=141.3 NAC 293
Very Quiet Operation, No Courtesy Tone and short hang time.
Most Users are configured for MixedMode operation Analog/Digital P25
If users are in Digital Mode, we will hear you if you ID in Analog Mode, and usually switch Modes

Do repeaters that support P25 always have a PL tone? I've noticed that most will provide PLs but don't require one to unlock the repeater to use P25. Is the PL for their analog side?

Also, is there some reason they don't use courtesy tone's on P25? It would be nice to know if I'm actually hitting the repeater or not (without having another radio/scanner nearby.)

[rapidcharger]

Originally Posted by nickcarr

Do repeaters that support P25 always have a PL tone? I've noticed that most will provide PLs but don't require one to unlock the repeater to use P25. Is the PL for their analog side?

Also, is there some reason they don't use courtesy tone's on P25? It would be nice to know if I'm actually hitting the repeater or not (without having another radio/scanner nearby.)

The mixed mode repeaters, that is, the ones that will work in analog and digital, usually have a PL tone for the analog side and a NAC for the digital side. PL tones being subaudible don't get picked up and converted to digital so those are just for analog operation only.

Unfortunately with digital, you don't hear the repeater coming back to you so you really don't know if you're getting in unless someone tells you or you hear yourself on another radio. Dstar has an echo-test feature though.

[W2NJS]

"Unfortunately with digital, you don't hear the repeater coming back to you so you really don't know if you're getting in unless someone tells you or you hear yourself on another radio. Dstar has an echo-test feature though."

This is flat-out not true. Even though you will not hear anything when you let go of the PTT on your radio, you WILL get a signal indication if your radio, such as an XTL or APX7500, has a signal indicator LED, which in the case of those two radios is yellow.

[rapidcharger]

Originally Posted by W2NJS

"Unfortunately with digital, you don't hear the repeater coming back to you so you really don't know if you're getting in unless someone tells you or you hear yourself on another radio. Dstar has an echo-test feature though."

This is flat-out not true. Even though you will not hear anything when you let go of the PTT on your radio, you WILL get a signal indication if your radio, such as an XTL or APX7500, has a signal indicator LED, which in the case of those two radios is yellow.

Well it isn't "flat-out" untrue then, is it?
It's only untrue if your radio has a signal indicator that you might find on those high end mobile radios.

[grem467]

Even the astro saber has a receive indicator in the form of an led on top of the radio. Every p25 radio I have ever seen has this which provides rx indication during the hang time. This is not limited to "high end" radios.

[MikeOxlong]

High end, low end, portable, mobile. Never seen any of them without some sort of busy channel activity indicator.