10 GHz amplifiers
Sep 6, 2024
Since conducting the receive tests on 10GHz during the ARRL EME Contest last month I’ve been busy finalising the sequencer and control circuits and started testing the amplifiers on the bench. I’m hoping to have transmit capability for the second leg of the contest in two weeks time.
Microwave amplifiers for amateur use, especially solid state ones, are a lot more expensive than HF and VHF amplifiers, a combination of lack of demand and high device prices. The W1GHZ transverter only outputs around +10dBm (1mW) so I need two stages to get to the +40dBm (10-12W) level, considered to be the minimum for EME when using a 1m dish. After considering whether to buy or build and a lot of searching I eventually settled on a driver amplifier from Rob, PA3GIE and a second-hand Kuhne unit for the final stage, purchased from Jac, PA3DZL.
I have limited test equipment for use at 10GHz, especially for accurate RF power measurements, but I do have a USB power sensor rated up to 6GHz. To establish how far off the power sensor was at 10GHz I took some initial measurements of the transverter on it’s own, then with the driver amplifier. Based on the specification of the PA3GIE amplifier I came to the conclusion that the sensor was reading around 3dB low at 10GHz.
The chart shows power output from the Kuhne MKU 3cm PA for different drive levels from the PA3GIE unit. Optimum drive level is around +21dBm (150mW), outputting +41dBm (13W) from the final stage. The input and output power measurements shown are after adjusting for the low reading in the sensor. When I have access to some suitable test equipment I’ll get it calibrated for 10GHz.