FT-7 Mod

Yaesu FT-7. Modification on the rear shows connectors for proper key-jack, RX and TX BNC connectors for transverter,
and RCA phono jack for audio output.
 

FT-7. Behind the VFO is some free room, it is used for
(1) a switch to disable the power amplifier when transverter is used (0.005-5mW RF out on transverter connector)
(2) SSB/CW agc derived squelch board
 

FT-7
 

Some of the modifications done for this rig (1982-1985):
1. CW transmit modification
2a. variable drive level using negative bias oscillator
2b. variable drive level, copying how it is done in FT-7B
3. 10M coverage: 28.0-29.0MHz
4. SSB squelch
5. Transverter facility, separate connections for RX and TX
-"- this also makes antenna connection for external RX (Drake R-4C or 2-B).
6. Normal key jack installed on the rear with KEY/PTT-connections
7. Changed CW xtal so that I can use USB for CW reception
Unfortunately no documents are available since somebody borrowed my book 3 years ago

                                      

Active CW key-filter
The ideal key filter is shown here. But application of this is only possible when you build the
transmitter yourself, normally you cannot decide to have the so easy task......
 

                                   

FT-7 key-filter.
Unfortunately the documents are not available and I am unable to provide the
cmponent values. It is important that the two stages have same threshold voltages or as
close as possible and this is found experimentally. The voltage swing is just somewhat more
than needed for perfect on and off state. In some cases the IF amplifier transistors should be
changed for better RF types with better keying (FT-221/FT-225). The problem with FT-7 and
FT-726 is that a germanium device is needed in the key-filter. It may be difficult to find
a type with sufficient high current gain, hfe=50 or more, so LA9DL used a silicon device in
his FT-726. This is difficult to tell whether it will work or not, particularly since I don't
have the rig and will prefer never have it in my house.

When writing FT-7, I receive several letters requesting info for FT-7B. They are completely different
styles and very little is directly similar. I haven't the faintest idea of FT-7B, only know that LA7XK
had one and I modified the FT-7B noiseblanker according to notes from LA7XK, Yaesu managed
to make a useful NB in FT-7B, while not in FT-7 and several later rigs, so one may still wonder
if they really understood when they succeeded or not.........
 

Clean CW signal from FT-7.
Wrote an article and it is published in SM-QTC nr 3/1983. The circuit diagram is shown below.
 

             

It is important that Q1004 is a high gain germanium PNP transistor like AC126 or it is not possible to get low enough
saturation voltage over this device. LA9DL used a silicon transistor in his modification for FT-727, but it requires some
changes, and I am not sure if it is possible here, since all voltages will be somewhat higher