Where we build things and learn stuff.

Winlink RMS Gateway

In February/March 2024, we built and deployed a Winlink RMS gateway.  There was a lack of RMS gateways in San Diego county, and we wanted to use the same TNC we built and install a gateway for everyone to use.  This was fairly easy, but did require a bit of equipment and dedication.  Read up on mail, and get connected!  You don't need a TNC to use Winlink mail, but you will need something like it for doing packet over RF.

We are looking for some members to volunteer on the gateway administration tasks.  You should know some basics about linux, have a good idea what the RMS gateway software does, participate in Winlink mail, and be willing to respond to some requests for service when available.  You will be given a login to this system using a VPN and 2 factor authentication, and will be placed on a mail alias for issues and requests.  We need at least three people for this, and if you are interested in learning how it works... we will teach you!  Spread the work and the knowledge around.  This would also be a great way for you to learn and build your own gateway using RMSGW or BPQ or other ham software of your choosing.  It is possible to integrate the RMS Gateway with AREDN.     

You can see it is possible to build a gateway with a $30 Baofeng radio, a $40 Nino-TNC, and a $35 Raspberry Pi-1 from 2014.  You probably have two of those things in your junk drawer.


WA6BGS-10  on 145.070MHz  click on Tools, zoom into San Diego county and you'll see our dot.  Choose "Packet" at the top of the map.


{12 page recipe document coming - this part takes a while}

WA6BGS-10 is our designation for the Winlink gateway.  I contacted the Winlink team and got the credentials necessary for a server deployment, and with some donated materials from Ray, one of the TNC's we built, and a plastic cutting board, we have a system that is ready for deployment.  This tiny NUC computer runs on 12v, so powering the entire setup from a single battery backup source will be easy.  There was a lot of software development and testing that went into the build, and we're running TWO verisons of Linux on this system using KVM virtualization.  The guest domain needs to run a linux version from 2018 because AX25 kernel development has not been maintained very well. The primary domain OS is the most current and patched release.  This deployment model is very stable (so far) and because we're virtualized, there is room on this little system for even more software projects.  It will take a long time to fill the disk at 1200 baud.

We're on the map for 1200 baud Packet, as an RMS gateway only.  After a while, we'll explore other tools and tasks for this system, and could easily add another radio or TNC, or build a second domain to run more packet protocols.  This is a great foundation for other things.

WA6BGS-10  at 145.070 MHz is where we are NOW!  Here is a picture of the equipment we assembled for the gateway.  Yes, that is a cutting board and the VHF radio is one Ray just had laying around.  The computer is a NUC form factor PC, and the TNC is one of the kits we build as a club.


If you are finishing your TNC solder project and are ready to attach your kit to a radio, use these guides to help you with the cable fabrication.

I suggest you find a 3-4 foot piece of STRANDED Cat5 cable because stranded will tolerate flexing much longer than solid cat5.  The TNC uses four wires from the DE9 connector for communication to your radio.   Pin 6 and 9 are bonded on the PCB as ground, only on version 4 of the boards.  We assembled version 4.  Tying them together in your cable will not hurt and it will make your TNC cable compatible with version 3 of the Nino boards.    For good measure you can tie all the other stripe cables together and ground them.  We are transmitting audio signals, so having a bunch of grounded wires inside shouldn't hurt.

Looking at the solder cups of the DE9 connector,  use the solid color wires according to the color codes in the drawings.  At the radio end, solder the appropriate rings tips and sleeves to your cable - use a multimeter to test the pigtail connectors ensuring you have selected the correct pin.  The supplied DE9 shell comes with several strain relief bushings and one of them fits perfectly around the jacket of a CAT5 cable.    Once the 9 pin shell is assembled, you can begin work on the radio end.

Note the drawings here.  This is what I have assembled and tested personally.    There are some builders who requested a DIN-6 and DIN-10 connector for their radio. Verify your radio DIN6 pinout instructions for connecting this cable.   The TARPN documentation page gives some detailed directions for setting the delay and TX audio levels.  The default settings we used during our assembly event will probably work well for most radios, but for a mobile unit using a dedicated packet port (not speaker and mic) you may need to adjust your TX or even modify the dip switch #1 on the SIGNALS group of switches.  My radio (FTM400) can take a 300mVp-p signal input, and the default settings for a mic only generate about 120mVp-p.  I sound weak.  You'll need a scope to properly measure this and the description is listed here.   Go do section 14-2  SIGNALS switch, and read up on Data vs Mic, and make necessary adjustments using RV1 (the 10k trim pot in step #18  )

Click to see three different hookup diagrams here.  For Baofeng and Yaesu radios, setting the radio volume around 33% to 50% seems to give good results with this TNC.  Setting the volume too high will overdrive the TNC and you may get poor reception.  An easy method for setting the volume on your HT (any of the models) is to slowly turn the volume up until the TNC CRC light begins to flicker, then back down until it stays off.  A volume setting too low means the TNC will have a hard time decoding the audio.  Set too high and the TNC thinks everything is a bad packet as you are overdriving the audio input.

The four ring Yaesu cable can be fabricated with the resistor and capacitor in-line, and shrink-wrapped to protect the junction.  The capacitor and resistor will fit inside some shrink wrap.  Add some hot-melt glue to help bind the small wires together, then shrink the tubing on top.


The Baofeng radios have several menu items you will want to change when using these HT radios for packet.  When you modify these settings for packet use, the radio will need some of them set back if you must field program your radio for a new repeater.  If you have never field programmed your Baofeng radio for a repeater... you should try it.

Some of these settings will be obvious, but others were suggested on various forums and I have collected them here for your convenience.
0 SQL = 0 off
2 TXP = high
3 SAVE = off
4 VOX = off
5 WN = wide
7 TDR = off
10 R-DCS = off
11 R-CTCS = off
12 T-DCS = off
13 T-CTCS = off
14 VOICE = off
25 SFT-D = off
26 OFFSET = 00.000
35 STE = off
36 RP-STE = off
37 RPT-RL = off
39 ROGER = off


The TARPN project has released STL files for 3d prints, based on the most current bill of materials.  This case will work for the TNC kits we are building.

TNC 3d print file TOP    TNC 3d print file BOTTOM 

Link to the assembly instructions for the TNC v4 

Here is another 3d print model for the TNC.  This has larger openings for the LED and USB/Serial and dip switches. 


UPDATE January 11, 2024 - Soldering workshop went really well.  Under the rosin haze of solder smoke and a whole bunch of soldering irons,  only Chuck.W burned himself, and David.K demonstrated his superior vision by assembling a board without needing glasses or a magnifier.  Some day David, you'll be right there with the rest of us, needing readers and bright lights so enjoy!  Three TNC builders successfully completed their boards during our session, tested and validated from a laptop.  The next phase of your build involves creating a TNC cable to interface with the radio.    Working with Rob.H, I was able to send a winlink P2P message across the room using our small HT's and the Nino TNC boards.  Huge success!  I can check that box now.

Thanks everyone for coming and putting your essential skills back to use, building something fun, and laying the groundwork for further packet communications.  For those who want 3d printed cases, these things take a few hours to produce and we will be in touch about getting them fabricated.  Bring your finished kits and laptops and radios back in February and we'll all sit in the same room and try packet communications with each other.  If you are not already connected and using the Winlink network, get started and bring your questions next month. 

If you need help fabricating the cable to your radio... we can help.  For Baofeng/Alinco/Anytone/Wouxon  the pinout is easy.  For Yaesu HT, it is one cable.  For your larger mobile units, you should have received a Mini DIN-6 or DIN-10 cable to go with your DE9 connector.  Stay tuned.

Ray.W and I are going to start the process for building a club RMS gateway, so more hams can use their new TNC's, and to help populate some much needed coverage back into the San Diego area.  

If you want the latest 3.34 firmware on your TNC (you have 3.33 right now), bring it in February.  This takes about 3 minutes to upload.


Bagged and double checked.

Ready for assembly.

DIGIKEY - arrived earlier than I thought, December 23.


Four layer boards and PIC33EP256GP502

December 20, 2023.  Parts begin to appear.

December 2023 - Project Proposal

Build an inexpensive kit TNC for the purpose of connecting your HT and laptop to the Winlink mail system, and explore additional Amateur Radio packet modes.  A project approved by the club members in attendance on November 9, 2023.

The purpose of this project:

The Project Parts:

The Project Plan:

The Other Things: