EMRFD Message Archive 8636

Message Date From Subject
8636 2013-05-07 05:10:10 VU3AUZ FT950 to Furuno Amplifier Interface
Hello All,

If someone has interfaced a Furuno Amplifier (PA2500) to FT950 Yaesu, do let me know. I am totally clueless about the Band data o/p of FT950. Neither the user manual nor the service manual mentions about the band data output. Somewhere in the net, i read that the band data output of FT950 is similar to that of the Ele K3.

After preliminary investigation I understood that FT950 gives a 4bit BCD data O/P, meanwhile the Furuno Amp accepts only 3 bit BCD band data. Is there some converter which can be used for this particular use case.?

Any idea about the ALC o/p levels from the PA2500 furuno Amp.?

Thanks in Advance,
8639 2013-05-07 13:44:01 ha5rxz Re: FT950 to Furuno Amplifier Interface
OK, I admit defeat, I've found the information
8643 2013-05-08 10:57:14 wb6tpu Re: FT950 to Furuno Amplifier Interface
The PA2500 takes in band select data on the DataA, DataB, and DataC pins (#'s 8,7 and 6 respectively on J804). Those 3-bits go to a TC4028 BCD to Decimal decoder chip and become the Band Select 1 thru Band Select 6 signals.

It looks like the bands in the PA2500 are mapped as follows"
Band1: 1.6 to 2.4 MHz
Band2: 2.4 to 3.6 MHz
Band3: 3.6 to 6.0 MHz
Band4: 6.0 to 10.0 MHz
Band5: 10 to 18 MHz
Band6: 18 to 30 MHz

You can snag a copy of the service manual which contains all the relevant schematics at the following URL:


In particular see pages 39 (switched LPF) and 40 (decoding logic).

With the above and the info for the FT-950 you should be able to figure out the mapping.



8644 2013-05-09 05:22:54 ha5rxz Re: FT950 to Furuno Amplifier Interface
OK, now I have the amplifier information it's easy. Your schematic is saved in the Files area as 'Amplifier Band Decoder.jpg

The IC is a common BCD to Decimal decoder and the outputs drive a diode matrix which gives you the correct band information. Each vertical line is a wired OR, easier to make modifications than using OR gates. Any diode will do but don't forget the 1K ohm pulldown resistors.

Take care