Converting the Kenwood TKR-820 for use with D-STAR is almost trivial. Here is what you need to do this project.
First you need a TKR-820 (or 720 for VHF) complete with duplexer, antenna, etc., tuned to your repeater pair. These are currently available on E-Bay (repeater and optionally a duplexer) for around $250-500 as pulled from commercial service. This is a nice little repeater which can run 5W for 100% duty cycle up to around 25W at a decreasing duty cycle. (I’m running around 10 Watts.)
Next you need to purchase a node adapter. I use the “Not Quite So Mini Hot Spot” (NQSMHS) board from ENIcommunications. It comes either as a kit for $80 or pre-built for $110. I chose the prebuilt version and this post is based on using this version of node adapter. There are others in the marketplace, but I cannot say if additional work will be required to use them with the TKR-820.
The next order of business is building the cable to go from the NQSMHS to the TKR-820. The NQSMHS uses a DE-9 plug and the TKR-820 has a great accessory jack which is a Molex 1625-15. I had a DE-9 socket in the junk box, and purchased the 1625-15PRT, socket and plug, from the local Fry’s Electronics.
The pinout for the DE-9 is as follows:
1 – Audio to Repeater (Modulator)
2 – Carrier Operated Squelch from Radio (Not actually used with the PA4YBR firmware, but I wire it anyway)
3 – Audio from Repeater (Discriminator Audio)
4 – Key Repeater Transmitter (PTT)
5 – Ground
9 – +12VDC (To power the node adapter, use this instead of USB power for better reliability)
The Molex 1625-15P (plug) pinout:
Jumper pin 1 to pin 11. This tells the Repeater it is being controlled by an external controller via the accessory plug (green wire in photo). Note: if your repeater happens to have an ID-8 module, you will get a CW-ID periodically. You want to remove or disable it.
Pin 2 is used for ground to the NQSMHS board.
Pin 3 is the modulator input (audio from the NQSMHS)
Pin 4 is the discriminator output (audio to the NQSMHS)
Pin 7 is a +12 VDC source (1 AMP – verify fusing when sourcing)
Pin 8 is the external PTT line
Pin 13 is the carrier operated squelch (COS) also documented as RUS by Kenwood.
Check all of your wiring. (DVRPTR added 9 March 2014)
|Jumper||-||-||1 to 11||Green|
Please verify these pinouts against documentation for each device. These work for my configuration, but your repeater may be different. No warranty is expressed or implied. Perform at your own risk.
You will note that no conditioning of lines, such as bypass capacitors, resistors, etc. are included in these instructions. My repeater and board just play together nicely.
This should complete your cable. If you haven’t guessed I used a piece of CAT-5 cable between the connectors. (Shielded/Stranded cable would be better – I also add some clamp on ferrite cores to this and especially the USB cable.)
Plug the DE-9 into the NQSMHS (as above), and the Molex 1625-15P into the repeater.
Attach the antenna (or service monitor) and power, adjust the NQSMHS and the modulator for approximately 1.2 Khz deviation. Adjust power for your use.
Using the firmware tools, insure that transmission is of the proper format (inverted/not inverted) and adjust the NQSMHS for proper detection of data coming from the repeater.
You can now fire up DVAR Hot Spot, with proper configuration. With a properly registered callsign and configuration you should now be able to link to repeaters, reflectors, and other HotSpots. Note: I tried a netbook to run DVAR with this NQSMHS and it would not key PTT, I think it was a USB drive level. switching to a full size computer solved the problem.
Here is the final product for the NW7DR repeater:
My repeater is literally a classic “garage repeater.” The TKR-820 should perform in traditional repeater settings, though for such high RF installations better cabling and packaging of the NQSMHS (shielded) is probably warranted. The NQSMHS could be mounted internally to the case, pushing the Molex socket inside and running the USB cable out the opening to the controlling computer.
My plan is to move this repeater over to G4ULF’s G2 compatible gateway software after release. I have a lovely 1U Linux server just waiting to replace the surplus Windows/XP tower currently attached to the NQSMHS.
You can see the Dashboard at NW7DR
Good luck with your conversion!