I have the 500Hz CW filter installed so I modified the
J29(SSB/SSB) location to provide selectable fast/slow AGC.
If you do not have the optional CW filter then the following
instructions will have to be adapted for your installation.
Remove D31 & D32.
CUT trace from pin 2 J29(SSB/SSB) to pin 2 J29(SSB/CW).
ADD wire from pin 1 of J28 to pin 1 of J29(SSB/SSB).
ADD a SP/ST switch to the top panel near the VOX
controls. There are several slots that can be used for
mounting a small slide switch.
Connect a pair of wires from J29(SSB/SSB) to the switch.
With both pins of J29(SSB/SSB) connected together SLOW
AGC is selected. When both pins are open, FAST AGC is
selected.
The Japanese have a power limit on 10 meters. In most rigs
from Kenwood there is a low power circuit connected to the
10 meter logic line. In the TS-120S that signal is labelled
B.
Somewhere in the unit there should be a splice block
connecting the B signal to the FILTER board. Locate the
wire going to pin 6 of the FILTER board connector and cut
that wire away from the splice block.
Add a SP/DT switch to
the top panel of the unit as above.
Connect the wire going
to pin 6 of the FILTER board connector to the center of the
switch.
Connect one side of the switch to 9v (can use pin 1
of J29(SSB/SSB) from mod above).
Connect the other side of
the switch to ground (speaker ground is OK).
Set the switch
to apply 9v and adjust VR2 for power output desired in low
power mode. I adjusted mine to minimum power, 35 watts.
A SP/DT switch can be added to the top panel of the unit to
provide WIDE/NARROW filter selection independent of
operating mode. For SSB operators who want the narrow SSB
filter and RTTY (and Packet DJB/90) operators who want the
CW filter in LSB connect each pin of J29(SSB/CW) to each
side of the switch. Connect 9v (from AGC mod) to center of
switch. Leave original J29 connector from mode switch
disconnected.
Here is one way to achieve full break-in CW with the TS-
120S:
Instead of connecting your key to the CW key input, connect
your key to the PTT line. Then use the external relay
contacts normally designed to key an external linear
amplifier to key the CW key line. If your keyer has a
weighting control you will want to set it somewhat heavier
than normal to overcome the keying delays through the relay.
I used this setup briefly and experienced no difficulties
but got tied of hearing the relays clakety-clack.