[amsat-bb] Foxtelem and FT-736R

kb2m at arrl.net kb2m at arrl.net
Wed Oct 14 22:04:01 UTC 2015

 Tom, you're really testing my memory, but I just can't remember the mod
exactly. I did this mod 15 years ago to a 736 I owned at the time. All I can
say is it does work at 9k6 when done. I'm sure the mod is out there


 I did find this and I'm 100% sure it's what I did. What a great blast from
the past. Good luck...

                       by James Miller G3RUH

These notes tell you where to get FM RX audio direct from the
discriminator, and where to modulate the FM TX varactor directly. 
These mods are non-destructive and take no more than a few
minutes.  The signals bypass the "DATA SOCKET" for high grade FM

The RX mod is suitable for:

 *  UOSAT-D 9600 baud downlink and terrestrial links
 *  1200 baud AFSK/FM Standard Packet - BUT IT'S UNSQUELCHED.

The TX mod is suitable for:

 *  FO-20/PACSAT uplink (1200 bps Manchester FM)
 *  UOSAT-D 9600 baud uplink direct FSK and terrestrial links
 *  1200 baud AFSK/FM Standard Packet.


FT736 -  FM Direct from Discriminator
Detected FM direct from the receiver discriminator is available
from the RX UNIT at the junction of R91 and C83.  These
components are shown in the top right-hand corner of the

Proceed thus:
 1. Disconnect FT736 from the mains electricity. (Safety).
 2. Remove top cover only.
 3. RX Unit is the vertical module on the left.
 4. Locate R91 which is about 25mm from the top, 50mm from the
radio rear. 
    the resistor is "on-end", and near a couple of glass diodes.
 5. Scrape any paint off R91's free end and wet with solder.
 6. Your RXaudio lead should be a fine screened cable;  connect  
  the inner to R91, and the outer braid to a ground point (e.g.  
  can of TO09)
 7. Route the cable out though any convenient aperture in the case.
 8. The discriminator sensitivity (FM Normal) as about 6 kHz/volt.

The link....


73 Jeff kb2m

-----Original Message-----
From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Tom
Sent: Wednesday, October 14, 2015 14:02 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Foxtelem and FT-736R

The manual for Foxtelem refers to pulling the discriminator signal out of
the Yaesu FT-736R for decoding.
However, it does not suggest a point on the circuit.
I'm thinking to try between Q20 and Q21 on the RX unit.  perhaps a 0.1 uf
cap to the collector of Q20?
Has anybody else tried this?
Thanks, Tom, NH6Y

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