After a long hiatus from ham radio and Allstar Link, I'm thinking about building a node again. I'm looking for collective knowledge on inexpensive modern radios and which ones can be hacked to support a discriminator output.
Back in the early 2000's when I was working with Jim Dixon to develop Allstar Link. I used Motorola Mitrek radios for a couple of my repeaters. These were bulletproof but were rockbound.
Nowadays, these radios are too bulky, and being rockbound are not very useful any more.
With the wide availability of inexpensive Asian radios (even though their front ends are crap), coupled with the fact that a lot of Allstar installations seem to be installed as home hot spots alleviates some of this requirement.
From what I've been reading about these inexpensive radios, they are so tightly integrated that a discriminator output is no longer available.
I have been reading that a lot of people no longer use the discriminator output, and instead use the COR/COS or vox RX signal detection modes. The problem with that is you lose flexibility in configuring the device.
What I want to know is, are there any inexpensive radios available which can be hacked to have a discriminator output, and, which ones seem to have the best RF performance.
Steve,
I thought all radios could be hacked for the output.
Perhaps you mean 'easily'.
Yea, I'm with you on those old Mitrek and Micor's.
Mitrek especially. Have you ever considered a crystal-plexer ?
I guess us old school folks have a hard time accepting some of this new stuff.
I happened to like Hamtronics rock radios. Simple. Those are all gone as well.
Many nodes anymore don't even have a radio. Stark compare to most being repeaters.
Sorry I did not directly answer that except in the first line.
EDIT: Perhaps look at the mobile units. Not HT's.
I looked into modifying my Mitreks, but that would be a very involved project as the TX channel element uses direct FM. Using something like the SI5351 and appropriate filtering would mean replacing the direct FM with phase modulator. Additionally there are triplers in the channel elements, and the RX channel element output is around 146 MHz or so. Careful RF design would be necessary to ensure that there are no additional spurs generated by the synthesizer.
I don't mind tearing into a radio to get the discriminator output. I have a complete setup to work on SMT boards. What would stop me however, is if the level of integration is so high that the discriminator output is contained within a custom integrated circuit and is processed within that IC and not available on a pin to be picked off with a coupling capacitor.
Yea, I get ya, those SOC chips. That is where the mobile suggestion came from, but I think some of those Chinese models may well use the same. I really have not look at any of the more recent diagrams.
I went looking on the web, where there use to be plenty of info on the subject 10-15 years ago, and only found this related.
Perhaps I used a outdated term in my search.
But in all honesty, you can build a hamtronics rock bound or synthesis unit as easy as many of these mod's. The diagrams are out there. I have them if you can't locate them.
Wish someone would make the circuit boards as I tossed my old etching kits.
As far as I know, these were a open source design. And I think they were published in some old QST.
I saw the progrock previously. It would work great with vintage phase modulated radios, but not with the Mitrek unfortunately. Maybe one of these days I may pursue the Si5351/phase modulator/filtering approach to make a frequency agile Mitrek (but no promises) I have designed built HF radios from scratch (see my QRZ page), but VHF design is much more demanding.
Research into newer vintage mobile might be the best approach as you indicated.
Edit: Oh, and by the way, I can design circuit boards as well. The HF radios have circuit boards designed with KiCad and fabricated at well known Chinese PCB fabs.
It's not a space I've spent a lot of time looking at, but the problem with the cheap radios - especially the 888s which used to be "the thing" to mod - is that the boards change wildly on the internals without any outside change in a model, revision, etc. And, of course, there's no official service manual or anything for them.
That's why most solutions I've seen at least in the "like an HT space" are using SA818 modules. Much easier to deal with and build reasonable audio around rather than hacking up the innards of an HT.
Otherwise, I'm still clinging to things like Motorola Radius/GM300s, CDM-1250s, etc. when I'm not using real repeater hardware.
Most any radio capable of 9600 baud packet is a good candidate. Icom ID800, 2830, several Kenwoods (including TKR820 repeater). I have used the Yaesu DR1X and GE Mastr 3. Also Quantar (I don't have first hand experience with the Quantar).. de nu5d
Yep. The 9600 packet RX output is essentially discriminator audio.
I'm gravitating towards the Motorola CDM1250 because there's a connector with flat TX and RX audio similar to what was on the Maxtrac series. The Maxtracs had a time out timer which couldn't be disabled if I recall. I need to find out if the CDM1250's can have the time out timer disabled in them.
Define "inexpensive modern" - make and model examples?
I anticipate...
Depending on the radio - 'top' of analog squelch control potentiometer - should be coming 'raw' from the discriminator (few radios actually have such now, mostly product detectors - close enough in some case.)
Radios with 'data' audio output for 9600 baud packet modems - that might provide adequate "white noise" level in the 4-6 Khz range noise detectors typically 'look' at.
I think I'm going to choose a couple of the Motorola CDM1250's for 403-470MHz. These seem inexpensive on the used market. Just have to avoid the narrowband only models. They have a nice 0.1 in. pitch connector on the back, and I know someone who can help with programming them.
Unless they released some at the very last dying breath of the Waris line, I've never seen a physically narrow restricted CDM radio; all you should need to do is revert to a slightly earlier version of the software from the final. This line doesn't restrict backtracking software versions like the public safety stuff (Astro/Astro25/APX, etc.). Of course, I could be in error but I've never heard of one...
WOW! Welcome back. I assume you’ve seen there has been work on app_rpt in the last couple of years. I hope you’ll take a look of the work that has been done over in GitHub and comment.
And yes, CDMs have a real discriminator output and make fine Allstar nodes, full ( 2 radios) or half duplex.
Thank you. I've been looking at all the work since I was gone, and you guys have made tremendous progress during my hiatus.
I retired in February of 2022. I scratch built some of my own HF rigs. (You can see them on my QRZ page). But now with the tariffs on electronic parts and PCB's from Asia, I had to find something else to do That's when I decided to take a look at where Allstar was, and if it would be worthwhile to get back in the game.
When Jim Dixon passed, it was at a really rough time in my life. I needed to find some people who would continue to maintain and support Allstar because I just didn't have the bandwidth to do it. I had to chose between making a living and supporting Allstar.
I'm afraid I'm seriously behind the eight ball when in comes to all of the changes that have been made to the code. I'll need some time to come up to speed again.
I'm really, really amazed at how Allstar has grown in the last couple of years.
That's when I decided to take a look at where Allstar was, and if it would be worthwhile to get back in the game.