I have built a 60W 1.2GHz amplifier some years back, and I thought I might share what I did……

This unit is based on the Kuhne MKU 23cm 60W Kit. 4W in, 60W out. The quality of the kit is outstanding, and the price is very reasonable. If you have a 23cm radio, but want some more grunt, then this is the kit for you.

Here is a picture of mine once put together.

You will notice on the left of the picture above, I have a 6dB SMA attenuator at the input, so I can safely drive the amplifier with a TS2000X (or any 23cm rig <=10W output). The blue cable you see is 50 ohm semi rigid cable, which is very low loss on 23cm. It is important to use quality cable at these frequencies, otherwise you are wasting your time.

Below is a picture of the frequency response curve of the amplifier – notice that I have tuned it for more gain at the top end of the band, where the repeaters are.

The T/R switching in the amplifier is handled by a mini-kits sequencer, that is triggered by the active low PTT output of the radio. I didn’t worry about trying to use RF sensing at this frequency, as it is not so simple to implement. (It can be done though) Here is the link to the website where you can buy the sequencer. Below is a photo of mine.

And finally, here is a shot of the amplifier all built up (but with the top cover removed)

I have since added a calibrated power meter to the front panel – see below…

This is based on the LM3915 logarithmic meter IC, and the reference is adjusted to calibrate the display to show actual watts into 50 ohms.

73 and keep building.