2× GS-35B HF Amplifier with GU-72 Driver
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A two-stage HF amplifier: a GU-72 driver sits in front of a pair of GS-35B, so 20–25 W of drive is enough to open the output stage fully.
Specifications
- Output stage: 2 × GS-35B (ГС-35Б)
- Driver: GU-72 (ГУ-72)
- Bands: 1.8–28 MHz
- Drive: 20–25 W
- Anode voltage: 3 kV
- Anode current: up to 1.4 A
- Power transformer: taken from an R-140 radio station
Circuit and build
The driver adds gain, so the amplifier runs from a low-power rig or from a regular one turned down. The price of any two-stage design is harder tuning and more work keeping it stable on the upper bands.
The transformer comes from an R-140 station. With up to 1.4 A on the anodes the supply has to carry a long, heavy load without a noticeable voltage sag.
About the GS-35B
Both output tubes are metal-ceramic triodes and need forced-air cooling.