Controllers
Here controller projects are described that were mostly developed for a specific application but are may easily be used in another context.
- Control unit with attenuator for automatic surplus ATUs using modern transceivers:
→ The KG-415 controller project, text, pictures and diagrams
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!
- LM335 Precision Temperature Sensor based analog Controller:
→ E311 2nd LO temperature controller: text, pictures and diagram.
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.
- A Switch-Mode Power Supply Module with EMI Suppression:
→ 28VDC Power from 230VAC for the BV83 Amplifier: text, pictures and diagram (see pages 7+8)
The unit described here supplies a single 28V 50ies tube audio amplifier module but can be used for similar purposes such as feeding a 671U-4 receiver/exciter.
- 400Hz inverters for airborne radios - an experiment:
(an extract from Signal 49 magazine published by VMARS)
→ 400Hz inverters for airborne radios. Part 1
This article describes some existing units and explores the use of a low-cost pre-assembled inverter PCB to generate single-phase 115V 400Hz power.
A hardware breadboard was built and the results analyzed and documented showing that one should strive for a better solution!
There was supposed to be a Part 2 describing such a more appropriate method, but so far it has not been written. Sorry!
The BV83 28VDC power supply. → click on picture to read about this project.
