SSR-III Hot Rod
Front Panel Machining
The panel after milling the 4 meter holes, the digital display hole, and drilling all the holes for the controls and
switches. For the notebook, some of the standard hole sizes are 3/8" (.375") for full-size rotary switches and
pots, with approx. 1" dia. bodies. Miniature toggle switches are 1/4" dia. Mini-pots are 6mm, about 17/64".
After machining, I stuck some of the components into their respective holes to check for interference. Note the
6:1 reduction drive at bottom-center. This is for the 50k ohm coarse frequency control. To the left of it is the
fine tune (or Delta Tune) control which is 10% of the overall R-value needed by the SR-III's oscillator. The black
control above that is a wire wound rheostat for the display (LED) brightness. The pot to the right of that, directly
under the circuit board, (with wires attached) controls the contrast of the LCD frequency display. All other
control functions can be seen on the front layout page.
Even though this panel was carefully laid out, and is a full-size 19" rack panel, it sure gets crowded awfully fast.
Next is to fabricate the meter clamps, the chassis pan, and cover. The preselector variable capacitor and
coarse tuning pot will be bracket-mounted to the chassis floor due to the requirements of their shaft and drive
systems. These details are the time consuming parts of the project - I'd rather be wiring the darn thing.
More mock assembly with the meters and digital display brackets fabricated and mounted ... more time
consuming details. I really want to start wiring before Christmas!!!
Here, I'm checking out the clearances for the potentiometers behind the panel and "finger room" between the
knobs. I wear a XXL glove and my wedding ring is a (US) size 15, the point being that this is as tight as I want
the controls to be. For obvious reasons, I detest micro-mini devices ... and at my age I can't read the little,
weeny legends and nomenclature (is that "RF GAIN" or "AF GAIN"?). See what I mean ... no pun intended.
Again, this panel is 19" long. The knobs are about 5/8" diameter and the Tuning and Delta Tune are 1" dia.
That should work out nice for my mitts.