Repeater

443.500 MHz + 5 MHz / CTCSS 146.2 / YSF
(Not currently coordinated or operating)

This homebrew repeater project has been a good learning experience, and rewarding because it contributes to the hobby and to the enjoyment of other area hams. So if you have a couple of old packet-capable analog FM radios laying around, maybe you will find a project like this as rewarding as I have.

With the ZUM Radio MMDVM controller, the repeater can operate in YSF, DMR, D-Star, P25, NXDN, or FM analog modes. The end goal of this project is to run YSF digital with FM analog for backup.

Components

• Yaesu FT-7800R transmitter
• Yaesu FT-7900R receiver
• Yaesu SMB-201 cooling fan
• ZUM Radio MMDVM repeater controller board v1.0 (F4 chip)
• Raspberry Pi model 3 B plus
• HighPi Pro case
• 16 GB or larger SD card
• WPSD controller software
• Home-brew wire harness, two mini DIN-6 cables run directly out of the case
• Bridgecom Systems BCD-440U duplexer
• Diamond MX-72H duplexer (the APRS digipeater iGate shares the repeater antenna)
• LMR-400 coax
• Diamond X-200A antenna at 42 feet, or Diamond X-50A antenna at 29 feet
  
  

Controller Wiring

Conduct a simple ohms test on your mini-DIN cable pins and wires to determine what color goes to what pin, just to be sure. In the Yaesu FT-7900R user manual, the pins are identified by both number and function. That, combined with the pin information from the ZUM Radio, the connections in the chart below will work properly for a duplex repeater and two radios, or a simplex hotspot and one radio. These are identified by TX (transmitter), RX (receiver), and TRX (transmitter/receiver) 

I cut the mini DIN cables to 18", passed them through holes I made in the case, and connected them to the controller board wire harness as indicated below.

Pin 1 (top left) PKD; Pin 2 (top right) GND; Pin 3 (mid left) PTT; Pin 4 (mid right) RX9600; Pin 5 (low left) RX1200; Pin 6 (low right) PKS (SQL)

Software

The WPSD MMDVM software image was provided by WPSD and is easy to load on a micro SD card with Raspberry Pi Imager, configured for your setup. Not much to explain here. Once WPSD is up and running, just fill out the fields with your data and save your configuration. 

I'm not covering the basic software setup, so if you need more information regarding this, comment below and I will add in whatever you ask for.

Frequency calibration adjustments are not needed in the WPSD software because no transmitter is directly tied in with the software, unlike hotspot transmitters such as the ZUMspot, and others. This is handled by the radios, and they were tuned at the factory to be FCC compliant.

If you are running Pi-Star, one extra thing you can add is a line in the "system cron" file to have the system reboot itself every Monday at 05:15. Below is a screenshot of the cron file with the added line,

15 5 * * 1 root reboot >/dev/null 2>&1 

This file is accessed by the Configuration/Expert/System Cron menu selections in the Pi-Star software. It's very easy to do, but be careful doing so, as everything in the file means something, even spaces. 

Using the highlighted text above, and the picture below as a reference for the cron file in Pi-Star,

1. Select all the text highlighted in blue above, and COPY
2. Place the cursor after the word "command" in the line "# m h dom mon dow user  command"
3. Hit ENTER to make a new line
4. PASTE the text in, as in the picture below
5. Click "Apply Changes" and it should now look like this

Edited Pi-Star system cron file

Transceivers

Setting up the radios is probably the easiest part. In this case, the Yaesu FT-7800R and FT-7900R radios are set to VFO simplex with packet mode enabled at 9600 bps so it is recognized by the MMDVM as a digital signal. The mode the MMDVM will recognize and repeat is determined by the mode selected in the controller's WPSD or Pi-Star software, so any of the digital modes supported by the MMDVM board can be used. The K9KMS repeater is set to YSF mode. When users' radios are in the "DN" setting, other data like DG-ID, distance, bearing, and their call sign are sent with each transmission. 

Antennas

A Bridgecom mobile duplexer and Diamond X-200A antenna serve in balance with the rest of the repeater's components. This low budget home-brew repeater, running 10 watts output, should have a good coverage radius. Further testing will find if this holds true with the area's terrain and obstacles where the repeater is located.

Cooling

Using this setup in simplex or duplex mode will cause the transmitting radio to transmit far more often than normal; the duty cycle will increase significantly. Limit the transmitter power to 20 watts or less, to extend the life of the transmitter.

Even so, the transmitter will get too hot, so a good cooling system such as the Yaesu SMB-201 or similar home-brew is recommended. A low-power relay placed in the SMB-201's switch wiring, and connected with the transmitter's fan wiring as a trigger, can be used to activate the SMB-201 fan when the transmitter's fan cycles on, if you're up to the challenge.

That's it. Need more information? Just ask.

updated: 05/14/2026