|The Thermistor can be seen attached to the FET|
The breadboard FAN circuit has be running for several hour - working as expected, it cycles the FAN ON and OFF (with speed control) as the Beacon Exciter transmits on its six minute schedule. The RF output is connected to a dummy load, as I have not looked at the PA signal on a Spectrum Analyzer yet.
|The Chaos of the Bench|
Testing in Progress
My goal was to build the new PA with the additional FAN Control circuit small enough that it would fit the same 1 x 1.5 inch layout of the current PA-47. I had to rearrange a few parts to make it all fit.
While doing some experiments with a new layout with DipTrace, I tried laying it out as a four layer board. Four layers makes the circuit layout much easier. but it would be a lot more expensive ( about 3 to 4X ).
New two layer PA-47 boards with Fan Control are now on order.