When I write about expanding coverage with digipeaters and gateways, I invariably get the "Who's gonna PAY for it?" emails.
It's not particularly expensive to set up a digipeater or gateway. Most hams have a spare dual-band HT, and that can be the RF end of a station, when attached to an exterior antenna. That antenna could be something as basic as a home-spun 1/4-wave ground-plane, or a home-made roll-up J-pole. For a gateway, internet access is required (wi-fi or Ethernet), but if someone didn't have that they probably wouldn't be reading this post. Even in a place without internet, such as a cabin, a digipeater is possible. All that is needed is a TNC (Terminal Node Controller) of some sort. In some cases, a computer is not needed.
The hardware TNC
The three best options for a cheap hardware TNC are the Microsat WX3in1, the Kantronics KPC3, and the Mobilinkd TNC4.
The Microsat TNCs can be found here. They are very reliable, commonly found in use, expandable, and easy to configure. The only downside is that they require an Ethernet connection, rather than wi-fi. Virtually every home router, and even the T-Mobile cellular modems, have an Ethernet connection. If you are setting up a digipeater, you don't even need to worry about Ethernet -- though it would make any digipeater more efficient. Looking at the Microsat website today, I see that the WX3in1 Mini is selling for $106. That's hardly a staggering sum. That device will allow you to run the RF end into it and will operate as a digipeater or gateway without any further hardware. The more advanced WX3in1 Plus 2.0 is $132. If you don't want to make a cable to connect the radio to the TNC, that would cost an extra $10. And you'll need a basic 12v wall-wart power supply, which most of us already have.
If you want a simple all-in-one solution, Microsat sells a 7w WIDE1-1 fill-in digipeater for $200. Just add an antenna and a 2A power supply.
A fancy new Kantronics KPC-3+ will set you back $250. This will allow you to set up a digipeater on APRS or "straight packet". On straight packet, you can run this as a BBS and foward messages to other stations. While the older KPC-3 is no longer available, they can be picked up on EBay for under $100. They will allow you to run an APRS digipeater connected to a radio and a basic 12v wall-wart power supply. No internet connection needed.
The Mobilinkd TNC4 costs $150, and needs to be connected to a computer over Bluetooth. As far as APRS applications are concerned, it's merely a modem. But it does have other capabilities for straight packet and M17, if you have patience. You can, of course, pick up an old Chromebook from Craigslist and install Linux on it. This will let you run YAAC as a client and operate a gateway/digi combo when connected to a radio. Or you can use an old Windows machine and run other APRS clients, such as APRSIS32 and UI-View. Cabling to connect the TNC4 to a radio is around $10. Specialized cabling can cost $50 or more from ham-made parts, if you choose not to make it yourself.
I found it worthwhile to buy a cable from hammadeparts.com to connect a Mobilinkd TNC4 to a Leixen VV-898, even though it was $50. Your mileage my vary, of course.
The radio
If you don't have a spare HT lying around, or you want more power than a 5w HT offers, there are options.
One option that I like particularly is the Leixen VV-898. It's a mobile rig that comes in both 10w and 25w versions. The 25w version will, of course, demand a real PSU. Bear in mind that APRS involves very short transmissions, and a PSU that would be inadequate for voice will be acceptable for APRS. The power demands are small enough that it could run on a battery with solar power to run a digipeater at a cabin.
The VV-898 has a sensitive front-end, even though it's a dual band. It also has SDR architecture. It may be a mediocre choice for areas with intermod, since it has below-average filtering, but it would be a solid option for suburban and rural APRS. While many would look down on their nose on such a rig for voice FM, on APRS this is actually a plus. The narrower audio frequency range makes it much more suitable for packet/APRS.
The 25w version can be bought on Amazon for $73, but can be had on AliExpress for about $55. The 10w version can also be found on AliExpress for the same price.
Certainly, there are better rigs out there. But, if you are looking to set up a TX gateway or digipeater for cheap, you can't beat the value. I used the 10w version for years on my home TX gateway, and it does the job in a suburban condo without creating interference with my neighbors. It can be run off a battery easily for emergency comms, too.
Another good option is the TYT TC-8000. While it's been discontinued, it still remains available on AliExpress for around $50. Make sure you are looking at the VHF option, rather than the UHF, since this is monoband. Avoid the dual-band versions, such as the TYT TC-8000D.
This is another case of a radio most hams would not consider for voice FM, but one that works well for APRS. It's a 10w HT that only has 16 channels, and it's a monoband. The big downside with this rig is that the PA tends to get overheated on long transmissions, and it only has 16 channels. But for APRS, none of this is an issue.
Being a monoband rig, the front end is pretty selective. Transmissions on APRS are under one second, so the PA never gets challenged. Only 16 channels? You only need one. The Kenwood-style connections mean cabling is simple.
While I use this in my car (with a battery eliminator) as a mobile APRS station, it could just as easily be used for a digipeater/gateway with a Microsat TNC. This is another case where the radio and TNC can be run off a battery with solar power indefinitely. In the metro, I've never had a problem reaching digipeaters and gateways with 10w and a trunk-mounted 1/4-wave whip.
Again, I will readily concede that there are better radios out there that can run 50w and that have native APRS. But, for $50, the TYT TC-8000 is a cheap option for a digipeater or TX gateway. We have 5w and 10w stations in the metro that make solid contributions, and a 10w digipeater or gateway in a rural or suburban location can make a big difference for both the network and the local area.
Software solutions
Software such as DireWolf or SoundModem can turn an old laptop into a TNC quite easily. The software is free, and free APRS client software can be installed to turn the station into a TX gateway easily. You can run an old analog scanner or SDR receiver into the audio input and create an RX-only gateway quite easily.
Summary
None of this requires a large cash outlay. If you already have a spare 50w VHF rig-- as many do -- you can just get a TNC like the Microsat and set up a digipeater or gateway for pretty cheap. I would suggest looking at sites like EBay, Craigslist, or various pawn shops for full-powered VHF rigs.
I understand that there are those out there who find a $200 expense to be a hardship. But let's not pretend that setting up an APRS gateway or digipeater requires thousands, and is out the reach of clubs or individual operators. A new PSU for an analog repeater can easily cost more than that, and nobody shrieks "Who's gonna PAY for it?" when one needs to be replaced.
So... $50 plus the spare radio you already have, with free software and cabling you make doesn't add up to an expensive proposition that requires you to screech at me. And you get a Linux laptop that can be used for other amateur radio purposes.
Something is always better than nothing. A cheap solution may not cover an entire county, but it's better than no solution at all.
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