Yaesu FIF-MX
This page was last modified 19:20, 9 July 2021 by Mars2000you.




The Yaesu FIF-MX is a digital CAT interface unit released in 1986. CAT means 'Computer Aided Transceiver'.

It can be used to control some radio-communication devices (receivers and transceivers), especially these models: Yaesu FRG-965, FRG-9600, FT-736R, FT-767.

The connection is made with a cable between the 6-pin DIN CAT output at the top of the cartridge and the 6-pin CAT input of the device, whose internal interface uses the RS-232C protocol.

This cartridge can be used with MSX1 and higher computers. It includes

  • a 16kB ROM that adds new instructions to MSX-BASIC - see Yaesu BASIC
  • a 16kB RAM (from 8000h to BFFFh)
  • an analog-to-digital converter (S-METER) that allows the computer to measure the relative strength of received signals (AGC voltage), for interactive operation between the computer and the receiver, when so programmed

The interface RAM is for RAM files on which you can memorize the program to control the receiver. By doing so, you can instantly run without starting the program each time you start the MSX, because the RAM is battery backed up so does not lose its contents.

The computer RAM from E900h to F0FFh is used by the communication data. The 7FF0h address is used in sending mode of the receiver.

Official price: ¥19,500


A software on tape is provided with the interface: the Yaesu CAT System. It uses the Yaesu BASIC instructions.

The content of the function keys is modified as follows when you launch this utility:

  • F1 - READ to read and display a previously selected channel
  • F2 - MODE to toggle between 6 receiver modes: LSB - USB - AM-N - AM-W - FM-N - FM-W
  • F3 - FSET to choose manually a frequency
  • F4 - STEP to toggle between 4 tuning steps when changing frequency in AM-W or FM-N mode: 5 - 10 - 12.5 - 25 kHz
  • F5 - PAGE to toggle between the 2 pages of the application
  • F6 - WRIT to add a channel (with title) in the RAM channel memory list
  • F7 - SLCT to select a channel (with select mark) in the RAM channel memory list
  • F8 - MSET to choose a channel from the RAM channel memory list, then switch to dial mode with the memory data
  • F9 - LIST to display the RAM channel memory list
  • F10 - SCAN to toggle between 4 scan modes: NON-STOP - FIND-EXIT - 10SEC STAY - STAY STILL

The data for 100 channels can be kept in the interface RAM from address B100h. 16 bits are used for each channel: mark (1 bit) - receiver mode (1 bit) - frequency (4 bits) - title (10 bits).



Yaesu FIF-MX
Yaesu FIF-MX top connector
Yaesu FIF-MX
Yaesu FIF-MX PCB underside
Yaesu FIF-MX underside


Yaesu CAT System
Yaesu CAT System