ON7UN Amateur Radio
 23cm Amplifiers
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23cm HPA
Mosfet Driver



We got a TH327 TV amplifier cavity, we need to get it working on 23cm. First thing was to modifiy the cavity, to work on 1296. Click here to see how it has been done.

The gain of this kind of amps depends on the tube, and the way the DC voltages are set up. We chose for a modern way to set up the different grids, in fact, we wanted to combine 'old' tube technology, with modern solid state devices. Since the expected gain is around 8 dB ( the more the better ), we need around 300 watt of driving power. These days, mosfet devices are available to give this driving power. The housekeeping of the tube amplifier is very important too. We wanted to get a very stable UG2, a well protected amplifier circuit, and complete remote control to the shack. Ian, G3SEK has described these matters in QEX magazine ( December 1997 ) and has made a circuit and board to feed and protect the Tetrode tubes. This board has been implemented in the amplifier. The board does the 600 V UG2 supply using mosfet's, it does the UG1, and all nessesary amplifier housekeeping tasks. The UA supply is the orriginal TV amplifier supply, using a 3 phase HV transformer, and 3 phase rectifiers. The circuit has been changed a bit to meet our needs. The HV supply is also being controlled by Ian's Tetrode Boards.



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