GS-34 PA for 23cm
Watercooled version, designed and built by
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This page details the GS-34 design shown on the previous page, repackaged in a water-cooled version. He uses it at home at the 200W output level. He tested it at home in St. Petersburg, and in Estonia at the XXXIX VHF/UHF/SHF festival, 28-29 June 2002. The picture below shows the PA after the demonstration at the festival. It does 400W out for low duty cycle transmissions like SSB, with minimal thermal drift!

From the left, Slava ES1AJ, Alex RW1AW, the PA, Ants ES6RQ & Stan ES4BW

Click on pictures for zoom

The GS-34 PA as it appears in the RW1AW shack. Driven by the barefoot TS-2000X (Note the TS-2000X is reading 1296.05000 MHz), with a little over 13dB gain, it provides 200W drift-free output. With 18 to 22W drive, one could achieve 400W output, or more, at 48 to 50% efficiency. At low duty cycles (such as SSB), there is little thermal drift!

All three modules, with top of cabinets removed. From left to right, the cooling resevoir, the PA and the power supply. All connections are in place between the modules.

The coolant module, with the 2.5 liter reservoir and showing the rear panel. This module includes an automatic mechanism for PA shutdown if water flow stops for any reason. The pump is also in this enclosure. The tank, pump and water tubing for this module are shown at right.

The PA with views of both front and rear panels. It is the same as the original design except water cooled. The vacuum relay removes B+ if water flow stops.

The power supply, showing front and rear panels. Output is 2250 VDC at 400 mA, approx. 12.6 VAC for the heater, + 12 VDC and +24 VDC.

Another look at the original GS-34 PA design. As noted above, this amplifier can do approximately 400W to 450W output at very low duty cycles without significant drift caused by thermal problems. The cooling module is capable of cooling two such PAs, and if two were paralleled using proper combiners, 800W of low duty cycle RF from 40W drive should be attainable.

The completed water cooled PA is shown at right. Click HERE for construction details of PA cavity.

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