Controllers

Here controller projects are described that were mostly developed for a specific application but are may easily be used in another context.

Surplus military and avionics ATUs from earlier decades are analog machines - despite their digital control circuits. They require “constant” RF power during tuning while presenting wild SWR excursions to the source. Modern transceivers - except perhaps units with a "tuner" output - will cut back power at high SWR to protect their finals. As the tuning ATU measures reflected power and looks for a minimum or a dip, it might stop and think to have found a match - of course it did not. Quite to the contrary: it found a high SWR! A temporary attenuator of 4-6dB switched into the transmit path will suffice to please the transceiver and to allow correct operation. This is shown on a sample project. With the setup described, or something similar, just apply power in CW or FM and turn on “tune” - it will work!

This project describes a controller for the heater coil of a local oscillator in a high performance classical receiver to replace a failed unobtainable proprietary thermostat.

 

Power Supplies

Here power supply projects are described that were mostly developed for a specific application but may easily be used in another context.