Symek IFD & FT-847
Created 2 February 2001
Some notes I made installing the Symek IFD on an FT-847...
First thing to say is be very, very, careful!! It's the most heart stopping surgery I've ever done on my FT-847: and I've done the INRAD filter, the headphone volume mod, fitted a new power switch, and a TX expansion mod. The IFD mod makes the other mods look like an walk in the park.
On the face of it it doesn't seem a very big deal - all you're doing is tapping into the radio's IF, just a couple of bits of miniature coax.
It took me six hours plus a night's rest from start to finish. Here's my list of caveats:
o One of the coils' ferrites lost its thread. Fixed this by disassembling the coil and wedging in a tiny bit of plastic wire insulation. Seems OK for now.
o The radio started showing S meter readings about 60dB down although sensitivity still seemed fine - I undid _everything_ and it still didn't work properly. A good night's sleep and magically everything worked fine again - I think maybe some damp got in from the soldering iron sponge (or I'm starting to dribble) and it evaporated away by the morning.
o Calibrating was a nightmare. I didn't find instructions the best for me as I couldn't seem to get the voltages mentioned. And as you can't tune the RX to the FM broadcast band there's not much to try it on other than wait for a live satellite unless you have WBFM TX too. Of course all my passes have been either in the middle of the night or during the day when I'm at work for the past week!
So as a true ham I made do with what I had...
In the end I did two things: fed the 10.7MHz IF of a real FM broadcast band radio into the HF antenna and made sure all was OK by listening to the AF out on the IFD. Sounded nice and crisp. Then I switched to sat mode, TXing 38.4kbps on the 2m band and RXing it simultaneously on 3rd harmonic on the 70cm band to give just enough deviation to make it work. There doesn't seem to be too much AF filtering on TX on the FT-847, allowing this feature to work.
The IFD fits on the outside of the radio fairly neatly at the rear in a small metal box (not supplied). Trouble is it's a struggle getting the normal PKT and RS232 cables in now as the new box gets in the way somewhat.
I believe someone's managed to get the unit inside the FT-847 by removing the speaker as an alternative.
In conclusion be very very careful! Seems to work a treat now. Haven't used it much on the sat as there's hardly been a convenient time yet! Talking to myself at 38,400 is very nice (I really should get out more). Netmeeting with video works a treat at this speeed! I'd be interested in others' experiences of course. My experience is likely not indicative of a general concensus.
73 Howard G6LVB
Position of C3371 (underside of IF board)
Installation of miniature coax #1 (underside of IF board)
Installation of miniature coax #2 (top of IF board)
Position of DC power tapping point on relay board on top of IF board
Location and insides of mounted IFD
Finished product mounted
Not much room for plugging in RS232 & PKT etc
Mail Howard, G6LVB