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College Campus M17 Repeater Ideas

 

Hello all:

Up front, I will not be “leading” or organizing this project (if it gains any momentum). I tend to be lousy at that in general, and at the moment I don’t have the bandwidth to do so. I’m hoping this can be “crowd” project here, and once all of the elements have been identified, maybe then I can come in and do a consolidation writeup. I’m guessing that enough of the pieces are out there (that I don’t know about) that it’s largely a light integration project of figuring out how to put all of the existing pieces together.

In Zero Retries 0165, I said: ()

I can easily imagine setting up localized M17 repeaters that cover perhaps a college campus, that will probably get more use with data / messaging than digital voice. How to set up such an M17 repeater will be a big focus of the M17 book that I’m working on.

I should have added in that mention that one mental model for this idea is that I’m absolutely confident that there a lot of students showing up on campus that will be using Meshtastic… and that it will grow very quickly if one person in a dorm is doing it and shows others how easy and inexpensive it is to get going.

Why focus on M17? I think there’s a good story that can be told to students about the virtues of M17 in large part because it’s open source, it’s hackable, and there’s now a large enough ecosystem of options for accessing M17 on RF for those that want to experiment, for example doing their own mods on inexpensive radios such as what OpenRTX is doing -?.

One of the touchstones of what resonates* with students about Amateur Radio was this informative talk at DCC 2018 -?Maintaining Student Interest in Amateur Radio by?Skyler Fennell KG0SKY -?. He describes with some enthusiasm the use of DMR because the radios are cheap.

One example is that there is no Amateur Radio club (there used to be) Western Washington University (WWU) -??here in Bellingham Washington. There used to be, and perhaps a project like this might serve to rekindle some interest in Amateur Radio.

WWU is an example of a small campus, small student body. But it should be able to scale to something bigger like this potential site for such a repeater is this from my time living near the Ohio State University campus -?.

One of the things KG0SKY said was that whatever a student wants to get involved with, it has to be cheap, Cheap, and CHEAP!

So… as much as I love the Connect Systems CS7000 M17, a $300 portable radio for a college student to use isn’t going to pass the “cheap, Cheap, CHEAP” test for large numbers of students getting involved in M17 over radio.

Some additional points to potentially support this idea:
  • The Open Source nature of this should play well not just with the students, but with the faculty.
  • The local M17 system could be incorporated into EE curriculum.
  • The local M17 system might even be able to be a project of the campus chapter of IEEE for students, which (perhaps some deeper pockets among the local IEEE community to help finance it) and it would be a great IEEE project.
  • While this project shouldn’t depend on the CS7000 M17 @ $300, it shouldn’t preclude it either for those students that want one and consider it a reasonable purchase.

So, here is the challenge to the M17 brain trust assembled here. To create interest about M17 on a college campus, I think we need to develop a couple of reference implementations for…
  • A minimalist repeater to do M17. This doesn’t have to be "cheap, Cheap, CHEAP”, because as a shared resource / infrastructure, it can probably be funded with perhaps a “quick” ARDC grant (especially if it can be semi-standardized) - we’d like to do the “Reference 1.0” M17 Repeater, here’s the cost that our facilities folks quote for installation at the high point on campus, please send money. I’m being a big flip about this, but it shouldn’t be complicated.
    • Of course, the Remote Radio Unit that Woj SP5WWP has been working on would be idea, but as far as I'm aware, that is still a project in development with only a few prototypes actually built. Since Woj isn’t seeking additional grants from ARDC, it doesn’t seem likely that the RRU will advance to the point where it’s available as a product, which is a key requirement to this idea.
    • What I’m aiming for is a low-power repeater sufficient to provide penetration coverage of a campus and not much beyond. The target user is a student in a dorm or nearby apartment or sorority with a tabletop system (see below) that can be put near a window.
    • The repeater should be all new parts; I understand the temptation is to say “Take two Motorola CDM-xxxx and…” and that instantly stalls things because those units are easy when you know how and have programming gear and documentation, but not easy if you don’t
      • UNLESS, there is a source of Motorola CDM conversions for Amateur Radio that has a reliable supply and a reasonable cost for turnkey conversion.
      • The expensive part is the duplexer - Any way around this? Perhaps cross-band like Repeater TX is on 222-225 MHz and Repeater RX is on 440-450 MHz?
      • Kenwood surplus commercial mobiles might be more easily hackable and thus more feasible?
    • Needs to be reliable, thus the quest for all new parts. Nothing will kill enthusiasm than a flaky repeater.
    • Should be compact so specify an available 5-10U rack that can be hung on a wall in an elevator room - or something.
    • Might need to have a repeater grade antenna with down tilt.
    • As tempting as it would be to make it “more accessible” by allowing all modes built into an MMDVM, I think that to encourage use of M17, the repeater should be generally designed to “lock in” M17 only. Otherwise the temptation is to go with all of the above, and at the moment, we don’t have a decent way to do transcoding, and I can’t think how this would be a unifying thing.
  • A minimalist M17 user unit.
    • Inspiration 1 for such a system is the G1LRO Amateur Radio Data Appliance -?
    • Inspiration 2 for such a system is the DigiPi -??(which, as far as I’m aware, does not do M17, or MMDVM)?
    • Fixed installation, not portable.
    • Low power, but at least 5 watts. There are embeddable radios out there that have flat audio I/O and at least 5 watts, I just don’t know what they are and don’t want to chase down the rabbit hole to find them - I have Zero Retries to write.
    • The antenna can be a simple one something like the Ed Fong DBJ-2 -??for which there are instructions online -?.
    • Not opposed to this being a “project” based on, say an MMDVM HAT on a Raspberry Pi, but again, all the parts have to be available off the shelf.
    • Should support data and voice.
    • DroidStar might be the right software for this idea, but it seems to only reference voice, not data.
  • Should have the ability to connect this repeater to any other repeaters that make sense. For example, in Boston it might be cool to connect all of the M17 repeaters together for Saturday Night chat (for the geeks that aren’t out partying).
  • To get around IT issues such as firewalls, I’m assuming that the ARDC 44Net VPN will be up and running to provide a publicly routable IPv4 address for such a repeater’s Internet connectivity (for example, BrandMeister).
  • I’m assuming that testing and licensing won’t be a major issue. My favorite model for Volunteer Examiner sessions is Laurel VEC -?.

I’m not imagining doing “coordination” of this activity, only to develop a reference implementation for the repeater and the user station targeted at a repeater scaled to a college campus, and inexpensive user terminals scaled (and cost-targeted) at students in dorms, etc.

There would be some evangelism of this idea, perhaps even a dedicated website.

Thanks for your ideas on this fantasy of mine!

Steve N8GNJ


*?Yeah, deliberate ?
 

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On 20/8/24 7:35 am, Steve Stroh N8GNJ via groups.io wrote:
Hello all:

Up front, I will not be “leading” or organizing this project (if it gains any momentum). I tend to be lousy at that in general, and at the moment I don’t have the bandwidth to do so. I’m hoping this can be “crowd” project here, and once all of the elements have been identified, maybe then I can come in and do a consolidation writeup. I’m guessing that enough of the pieces are out there (that I don’t know about) that it’s largely a light integration project of figuring out how to put all of the existing pieces together.

I'll have a stab at thinking out loud.

So, here is the challenge to the M17 brain trust assembled here. To create interest about M17 on a college campus, I think we need to develop a couple of reference implementations for…
  • A minimalist repeater to do M17. This doesn’t have to be "cheap, Cheap, CHEAP”, because as a shared resource / infrastructure, it can probably be funded with perhaps a “quick” ARDC grant (especially if it can be semi-standardized) - we’d like to do the “Reference 1.0” M17 Repeater, here’s the cost that our facilities folks quote for installation at the high point on campus, please send money. I’m being a big flip about this, but it shouldn’t be complicated.
    • Of course, the Remote Radio Unit that Woj SP5WWP has been working on would be idea, but as far as I'm aware, that is still a project in development with only a few prototypes actually built. Since Woj isn’t seeking additional grants from ARDC, it doesn’t seem likely that the RRU will advance to the point where it’s available as a product, which is a key requirement to this idea.
    • What I’m aiming for is a low-power repeater sufficient to provide penetration coverage of a campus and not much beyond. The target user is a student in a dorm or nearby apartment or sorority with a tabletop system (see below) that can be put near a window.
Currently, the best candidate would be a couple of FM data radios.? I'm not sure what's available these days, but there used to be units on the market in the 5-10W range.? The obvious choice for a controller is a MMDVM (like the one from Repeater Builder).
    • The repeater should be all new parts; I understand the temptation is to say “Take two Motorola CDM-xxxx and…” and that instantly stalls things because those units are easy when you know how and have programming gear and documentation, but not easy if you don’t
      • UNLESS, there is a source of Motorola CDM conversions for Amateur Radio that has a reliable supply and a reasonable cost for turnkey conversion.
      • The expensive part is the duplexer - Any way around this? Perhaps cross-band like Repeater TX is on 222-225 MHz and Repeater RX is on 440-450 MHz?
BI7JTA has some inexpensive (< $100 USD) notch duplexers that might do the trick on 440 MHz, available new on his website.? I've seen similar from other sources as well, they're still being made, and they'll easily handle the 5 MHz split.
    • As tempting as it would be to make it “more accessible” by allowing all modes built into an MMDVM, I think that to encourage use of M17, the repeater should be generally designed to “lock in” M17 only. Otherwise the temptation is to go with all of the above, and at the moment, we don’t have a decent way to do transcoding, and I can’t think how this would be a unifying thing.
That's just a matter of configuration.? It's up to the administrator of the system to configure the system, and all one needs to do is enable M17 and disable all other modes.? Job done.? Besides the RRU, I'm not aware of any other controllers that can do M17.? The host software can be run on a Pi or a PC (so using an industrial embedded PC is an option for reliability, there's USB versions of the MMDVM on the market).
  • A minimalist M17 user unit.
    • Inspiration 1 for such a system is the G1LRO Amateur Radio Data Appliance -?
    • Inspiration 2 for such a system is the DigiPi -??(which, as far as I’m aware, does not do M17, or MMDVM)?
    • Fixed installation, not portable.
    • Low power, but at least 5 watts. There are embeddable radios out there that have flat audio I/O and at least 5 watts, I just don’t know what they are and don’t want to chase down the rabbit hole to find them - I have Zero Retries to write.
    • The antenna can be a simple one something like the Ed Fong DBJ-2 -??for which there are instructions online -?.
    • Not opposed to this being a “project” based on, say an MMDVM HAT on a Raspberry Pi, but again, all the parts have to be available off the shelf.
    • Should support data and voice.
    • DroidStar might be the right software for this idea, but it seems to only reference voice, not data.

I'm not as good on this side, but I do have an idea what bits are out there currently, and all being open source, there's room for derivative works.

Client side implementations that I know of.? I'm sure most are voice focused, though it's all open source.

M17Client (turns a MMDVM+radio or a hotspot into a client modem).? Needs a host (PC or Pi) and MMDVM/MMDVM_HS board.? Interface is either X based (local HDMI monitor, keyboard, mouse and audio device) or Nextion touchscreen.? For the requited power, a suitable data capable radio would be needed with an MMDVM modem board.

Module17 (hardware based modem running OpenRTX).

TNC4 - not cheap, but mentioned because this a platform that's relatively easy to do data on, and an example of M17 over KISS.

M17tools - software only implementation, uses sound device to interface to radio (Digirig is a common choice of interface used here).

Just to name a few.? However, in general, voice support is more mature than data support.? This is where the universities might be able to contribute.

Anyway here's where the student body (EE/CS) might get involved in creating their own in house terminal that meets their needs - demonstrating the power of open source for customisation and coming up with something that meets their needs better than some outside party could produce.

  • Should have the ability to connect this repeater to any other repeaters that make sense. For example, in Boston it might be cool to connect all of the M17 repeaters together for Saturday Night chat (for the geeks that aren’t out partying).
M17-UNI ;)?? If that reference wasn't obvious, someone setup a reflector on one of the campuses, at a site the other campuses can access it, which can be used for inter campus hookups.? An RF based interconnection protocol hasn't yet been defined (excluding anything that can carry IP of course ;) ).
  • To get around IT issues such as firewalls, I’m assuming that the ARDC 44Net VPN will be up and running to provide a publicly routable IPv4 address for such a repeater’s Internet connectivity (for example, BrandMeister).

The Brandmeister reference here makes no sense.? BM is a DMR network, no relevance.? The VPN would route all Internet traffic via UCSD, not goof for high performance applications, but perfectly fine for intra VPN traffic.

Anyway just a few thoughts that come to mind.


-- 
73 de Tony VK3JED/VK3IRL

 

  • UNLESS, there is a source of Motorola CDM conversions for Amateur Radio that has a reliable supply and a reasonable cost for turnkey conversion.
AAM25RKC9AA1AN (CDM750)
AAM25RKD9AA2AN (CDM1250)
AAM25RKF9DP6AN (CDM1550)
?
All can be had for a range of price from $150 - $300 each. Not that terrible for a pair, and they're really good radios. The important parts are the R in the 6th position, and the 9 in the 9th position in the model number. Those radios should be 403-450MHz and still be wideband (25kHz) capable. Programming them is simple, if you have a cable - I'm sure lots of local clubs would have one to spare and would be helpful in programming.
?
  • The expensive part is the duplexer - Any way around this? Perhaps cross-band like Repeater TX is on 222-225 MHz and Repeater RX is on 440-450 MHz?
You can get a 50 watt duplexer for $120-$150 on eBay. Some sellers will also tune it for you before shipping, though testing it with a specan, tracking generator, and a VSWR bridge might need to be done after shipment. Again, check with your local club. I can pretty much guarantee that any club running a repeater themselves would have the tools. Crossbanding would need a radio that covers both bands, or two radios that cover one band each.
?
  • Kenwood surplus commercial mobiles might be more easily hackable and thus more feasible?
Maybe. But the price would be about the same as the Motorola radios I think.
?
RE: Radios (CS7000-M17) - a grant for a few should be easy to come by, if included with a DIY repeater. Loan the radios out to students, like a library book. Let them hack at it, maybe provide firmware help to OpenRTX.
?
Some other options that I didn't see (or maybe glossed over) for data: TNC4 or NucleoTNC. The latter would be a fun build-it-yourself project, and possibly garner interest in the software side too.
--

Steve KC1AWV
M17 Project
 

I ran across the Retevis RT97s, which seems to check most of Steve's boxes:
?
It seems to be a packaged low power (5-10w) UHF repeater including a duplexer. The RT97S model includes a DB9 that *should* allow interfacing an MMDVM modem. Of course, I haven't tried it so YMMV. Supposedly Retevis will set it up for your frequencies and tune the duplexer before shipping. The best part is the price, less than $500. The offer a DMR variant, the RT97P, for a couple of hundred bucks more, so perhaps they could be convinced to come up with an M17 version, especially if there was a clear market, e.g. a bunch of colleges with ARDC funding.
?
Jim
N1ADJ
 

I've got a 40w UHF Motorola GR1225 with a duplexer that I'll donate to the project.? I know that the MMDVM board can be fitted to it.? Let me know if you want it, Steve.? -Joe
gr1225-case-f-and-r.jpg


On Mon, Aug 19, 2024 at 2:35?PM Steve Stroh N8GNJ via <steve.stroh=[email protected]> wrote:
Hello all:

Up front, I will not be “leading” or organizing this project (if it gains any momentum). I tend to be lousy at that in general, and at the moment I don’t have the bandwidth to do so. I’m hoping this can be “crowd” project here, and once all of the elements have been identified, maybe then I can come in and do a consolidation writeup. I’m guessing that enough of the pieces are out there (that I don’t know about) that it’s largely a light integration project of figuring out how to put all of the existing pieces together.

In Zero Retries 0165, I said: ()

I can easily imagine setting up localized M17 repeaters that cover perhaps a college campus, that will probably get more use with data / messaging than digital voice. How to set up such an M17 repeater will be a big focus of the M17 book that I’m working on.

I should have added in that mention that one mental model for this idea is that I’m absolutely confident that there a lot of students showing up on campus that will be using Meshtastic… and that it will grow very quickly if one person in a dorm is doing it and shows others how easy and inexpensive it is to get going.

Why focus on M17? I think there’s a good story that can be told to students about the virtues of M17 in large part because it’s open source, it’s hackable, and there’s now a large enough ecosystem of options for accessing M17 on RF for those that want to experiment, for example doing their own mods on inexpensive radios such as what OpenRTX is doing -?.

One of the touchstones of what resonates* with students about Amateur Radio was this informative talk at DCC 2018 -?Maintaining Student Interest in Amateur Radio by?Skyler Fennell KG0SKY -?. He describes with some enthusiasm the use of DMR because the radios are cheap.

One example is that there is no Amateur Radio club (there used to be) Western Washington University (WWU) -??here in Bellingham Washington. There used to be, and perhaps a project like this might serve to rekindle some interest in Amateur Radio.

WWU is an example of a small campus, small student body. But it should be able to scale to something bigger like this potential site for such a repeater is this from my time living near the Ohio State University campus -?.

One of the things KG0SKY said was that whatever a student wants to get involved with, it has to be cheap, Cheap, and CHEAP!

So… as much as I love the Connect Systems CS7000 M17, a $300 portable radio for a college student to use isn’t going to pass the “cheap, Cheap, CHEAP” test for large numbers of students getting involved in M17 over radio.

Some additional points to potentially support this idea:
  • The Open Source nature of this should play well not just with the students, but with the faculty.
  • The local M17 system could be incorporated into EE curriculum.
  • The local M17 system might even be able to be a project of the campus chapter of IEEE for students, which (perhaps some deeper pockets among the local IEEE community to help finance it) and it would be a great IEEE project.
  • While this project shouldn’t depend on the CS7000 M17 @ $300, it shouldn’t preclude it either for those students that want one and consider it a reasonable purchase.

So, here is the challenge to the M17 brain trust assembled here. To create interest about M17 on a college campus, I think we need to develop a couple of reference implementations for…
  • A minimalist repeater to do M17. This doesn’t have to be "cheap, Cheap, CHEAP”, because as a shared resource / infrastructure, it can probably be funded with perhaps a “quick” ARDC grant (especially if it can be semi-standardized) - we’d like to do the “Reference 1.0” M17 Repeater, here’s the cost that our facilities folks quote for installation at the high point on campus, please send money. I’m being a big flip about this, but it shouldn’t be complicated.
    • Of course, the Remote Radio Unit that Woj SP5WWP has been working on would be idea, but as far as I'm aware, that is still a project in development with only a few prototypes actually built. Since Woj isn’t seeking additional grants from ARDC, it doesn’t seem likely that the RRU will advance to the point where it’s available as a product, which is a key requirement to this idea.
    • What I’m aiming for is a low-power repeater sufficient to provide penetration coverage of a campus and not much beyond. The target user is a student in a dorm or nearby apartment or sorority with a tabletop system (see below) that can be put near a window.
    • The repeater should be all new parts; I understand the temptation is to say “Take two Motorola CDM-xxxx and…” and that instantly stalls things because those units are easy when you know how and have programming gear and documentation, but not easy if you don’t
      • UNLESS, there is a source of Motorola CDM conversions for Amateur Radio that has a reliable supply and a reasonable cost for turnkey conversion.
      • The expensive part is the duplexer - Any way around this? Perhaps cross-band like Repeater TX is on 222-225 MHz and Repeater RX is on 440-450 MHz?
      • Kenwood surplus commercial mobiles might be more easily hackable and thus more feasible?
    • Needs to be reliable, thus the quest for all new parts. Nothing will kill enthusiasm than a flaky repeater.
    • Should be compact so specify an available 5-10U rack that can be hung on a wall in an elevator room - or something.
    • Might need to have a repeater grade antenna with down tilt.
    • As tempting as it would be to make it “more accessible” by allowing all modes built into an MMDVM, I think that to encourage use of M17, the repeater should be generally designed to “lock in” M17 only. Otherwise the temptation is to go with all of the above, and at the moment, we don’t have a decent way to do transcoding, and I can’t think how this would be a unifying thing.
  • A minimalist M17 user unit.
    • Inspiration 1 for such a system is the G1LRO Amateur Radio Data Appliance -?
    • Inspiration 2 for such a system is the DigiPi -??(which, as far as I’m aware, does not do M17, or MMDVM)?
    • Fixed installation, not portable.
    • Low power, but at least 5 watts. There are embeddable radios out there that have flat audio I/O and at least 5 watts, I just don’t know what they are and don’t want to chase down the rabbit hole to find them - I have Zero Retries to write.
    • The antenna can be a simple one something like the Ed Fong DBJ-2 -??for which there are instructions online -?.
    • Not opposed to this being a “project” based on, say an MMDVM HAT on a Raspberry Pi, but again, all the parts have to be available off the shelf.
    • Should support data and voice.
    • DroidStar might be the right software for this idea, but it seems to only reference voice, not data.
  • Should have the ability to connect this repeater to any other repeaters that make sense. For example, in Boston it might be cool to connect all of the M17 repeaters together for Saturday Night chat (for the geeks that aren’t out partying).
  • To get around IT issues such as firewalls, I’m assuming that the ARDC 44Net VPN will be up and running to provide a publicly routable IPv4 address for such a repeater’s Internet connectivity (for example, BrandMeister).
  • I’m assuming that testing and licensing won’t be a major issue. My favorite model for Volunteer Examiner sessions is Laurel VEC -?.

I’m not imagining doing “coordination” of this activity, only to develop a reference implementation for the repeater and the user station targeted at a repeater scaled to a college campus, and inexpensive user terminals scaled (and cost-targeted) at students in dorms, etc.

There would be some evangelism of this idea, perhaps even a dedicated website.

Thanks for your ideas on this fantasy of mine!

Steve N8GNJ


*?Yeah, deliberate ?



--
Joe Hamelin, W7COM,?Portland, OR, +1 360 474 7474
 

Just gonna drop this here (regarding M17 as a curricular tool):

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