I've recently completed a modification to my TenTec Scout to
allow instant QRP operation. It's the one originally suggested
by David, K1OPQ, and it's so easy to do and works so well I
thought others might be interested if they missed the original
description. It allows a change from full 50 watt output to less
than 5 watts at the flip of a switch.
As all Scout owners know, the rig as it comes from the
factory has an arrangement for changing the power output that is
both primitive and frustrating. It involves probing through a
hole in the bottom of the case with a small screwdriver in the
hope of making contact with the power control pot, R21.
Others have suggested complicated modifications, such as
moving the potentiometer to a spot outside the case, but this
involves removing the existing pot from the PC board and running
a ribbon cable.
David's modification is so simple that almost any klutz (me
included) should be able to handle it. It requires a 390 ohm
resistor, a small SPST switch similar to the one on the rear
panel of the Scout that's already used for switching between
power output and SWR readings, and a length of #26 solid
insulated wire, or something close. I found it best to leave the
top cover of the rig in place while working on the bottom side
and to place a towel on the workbench to protect the finish.
The power control potentiometer is not hard to find. The
hole in the bottom of the case points straight to it! However,
it took some headscratching (how to connect? how to connect?)
before I discovered that the pot is mounted an eighth of an inch
or so above the circuit board. This means there's just enough
room, using a fine-tipped soldering iron, to put a little solder
on the wiper of the pot and then loop the pre-tinned end of the
#26 wire around the wiper and solder it, quickly, in place.
(Note: if you don't have a soldering iron with a suitable tip,
don't attempt this project!)
That's the hard part. Now drill a hole for the switch in
the back panel. I found mine fitted nicely just below the SWR
switch and above the power connector. I drilled a small lead
hole, using a hand drill, and then carefully enlarged it, one
size at a time, with an electric variable speed drill, eventually
reaching the quarter-inch size needed for the switch. Be sure to
get rid of all the drill shavings.
The next step is to cut the other end of the wire which you
previously soldered to R21 to a suitable size to reach the switch
when it is mounted, strip a quarter inch or so of insulation and
solder to one terminal of the switch. Solder one end of the 390
ohm resistor to the other switch terminal. Cut the leads to a
suitable length so that the free end of the resistor can be
soldered to a nearby ground lug after you've mounted the switch
on the back panel (a real test of dexterity). Use spaghetti on
the leads, if desired.
That's it. Set the pot so that the rig shows full power on
the "high" position of the switch. When the switch is thrown the
other way, my power output drops to about 4.5 watts.
-- Ron VE3SP
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