During RTTY/AMTOR operation it is usefull to have an narrow filter
to reduce QRM from other stations. It is possible to use the
narrow CW filter of the FT 757 for SSB, because of the shift/width
For the SPDT switch I am using the MOX switch on the front panel.
It is a 2 pole toggle switch and you habe to cut the PCB between
the contacts. Further you have to remove all wires from the MOX
Cut the connection between cathode of diode D 102 and a 150
OHM resistor on RF UNIT. This resistor is not shown in service
manual,but it exists on all rigs later LOT 4.
Take a new diode (1N914 or similar) and solder the cathode to
the open end of the 150 Ohm resistor. Connect the anode to middle
contact of a double pole toggle switch.
Connect the OFF contact to pin 5 of J10 (SSB 8V) and ON
contact to pin 8 of J10 (TX 8V).
Take another Diode of the same type and solder it's cathode to
pin 1 of J09 and the anode to ON contact of the second pole of
Connect the switching (middle) contact of second pole to
pin 7 of J10 (RX 8V). The OFF contact will be let free.
Attention : There are some errors in the Service Manual. F.e the
filter connection is shown wrong. If you want to have a corrected
circuit diagramm and complete modification diagramm together with
some other modifications, write to Roland Robic OE6RCD, Augasse
15, A-8430 Leibnitz, Austria.
Please enclose 3 IRC (Europe) or 5 IRC (outside Europe Airmail)
for covering postage.
Best 73's de Roland OE6RCD @ OE3XBS.AUT.EU