I want to discuss the technical possibility of using an ASL3 hotspot in a very atypical manner.
Please stick to the technical aspects and do not wander off into in FCC rules etc... You will see why if you read on.
Background
A US based Medical Missionary group has an older VHF repeater in Honduras that they own/operate. It is licensed through the local authorities there.
Establishing AllStarLink access to the repeater could be very useful.
Use case scenario
Medical staff in the city where the repeater is located have VHF radios to communicate within their team.
Remote medical teams venture out into the country and set up clinics. There is little to no infrastructure (commercial power/comms) in these remote locations.
The remote teams are equipped with small generators and HF radio equipment which is primarily used for WinLink. A Starlink system was recently added to the team portfolio for internet access. An HT and a mobile hotspot would be useful to these remote teams as it would allow them to connect to the repeater in the city and talk to the medical staff there.
Problem Statement
The roadblock in this scenario is establishing AllStarLink access to the repeater. The repeater is very old, there is no manual, there is no programming cable, and there is no local knowledge to program the repeater even if the manual and cable were available. In the long term the repeater needs to be replaced and there is an effort underway to seek a grant for that purpose.
A short term HACK has been proposed:
Set up a hotspot in very close proximity to the repeater - most likely in the building where the repeater is housed and where there is internet and commercial power available.
Program the hotspot to look just like any other HT accessing the repeater.
Frequency/offset/CTCSS etc...
Access the repeater from anywhere in AllStarLink (including the Honduran jungle) by connecting to the node of the simulated HT. Think of it as functioning as an HT extender...
In theory this should work, shouldn't it? If not, why not?
What are the potential pitfalls?
Might the HOTSPOT front end become overloaded by the strong repeater signal?
Should DTMF control of the hotspot be disabled in order to only allow incoming connections?
Are there other technical or security concerns you can think of?
Thanks for any constructive feedback you are able to provide.
Yes, You can set up an ASL node to act like any other user of the repeater. (a half-duplex/simplex radio node setup) You are basically creating an internet connected remote base radio tuned to the repeater’s frequencies.
Overload of the hotspot radio’s front end should not be an issue, as long as you you don’t put its antenna parallel with the repeater antenna. (thus feeding WATTS of power into the receiver) If it were me, I’d put the node radio on low power and use a simple ground plane antenna (mag mount) on top of a file cabinet or similar. If you don’t have internet at the repeater site, the remote node could be anywhere in the nearby area where internet may be more available.
You say the current repeater is “old”. That is a matter of perception. Do you know the manufacturer and/or model number? Unless it’s something homebrew with two mobiles or something kluged together, there may be an easy way to interface ASL to the current machine.
The biggest pitfall I can think of with a simplex link into a repeater is that if the link is transmitting, there is no way to shut it down via DTMF remotely. (Half duplex) This may or may not be an issue.
As far as security goes, I would use private node numbers. That should keep all but the determined folks off the frequency.
As far as the remote end goes, you can most definitely use another simplex node/hotspot. If you have folks in the remote areas with cellphones on their hips, you can use an IAX app on the phone and remote into the link node without using HTs.
+1 with the idea of just interfacing with the repeater even if it’s “old”. The ham community has done a fantastic job (IMO) of making old manuals and schematics available for all types of strange, hard to find stuff relatively quickly. If it is too old or hard to figure out, maybe just replace it for the time being with some cheaper commercial radios (dare I say maxtracs?) that are well documented and can be found on local places like marketplace for less than a lunch in the US, just be sure to vet anything with a little due diligence. Even swapping the radios seems like the same amount of work as the remote HT idea and has less stuff to break.
Just seems wrong to put something generating RF in the same facility as the repeater to merely get audio and signaling across the room/building.
This subject comes up more often than you may think. Take a look around here with the search tool for topics such as "in-band" or "in band linking" or maybe "no internet at repeater".
You'll probably find my comments on the subject in a number of places and why I think is a really bad idea for a number of reasons. But hey, it's ham radio. We learn, in part, by trying things. So have at, keep asking questions and enjoy the journey.