50MHz (6m) Linear Amplifier for FT690, 2.5W in 25W out. Made in Dorset UK

  

This amplifier is supplied in a plain diecast aluminium box 120x92x56mm with a black heatsink. The amplifier circuit and layout was created by me, Antony Nailer G4CFY of Spectrum Communications, in November 1991 and continued with the original PCB until mid 2020 when a new PCB was laid out. It was originally designed for use as a single stage amplifier for 2m or 4m or 6m with devices to give 25W output.

This 25W versions is the ideal. It uses an SD1229 device with a forward bias of 40mA and is tuned for peak power output consistent with an input SWR better that 1.2:1. It comes with a 1 metre 32/0.2mm red/black twin power lead and runs from a 13.5V 5A supply and usually draws 3A continuous on DATA or FM, or peak in the case of SSB or CW. This is NOT a wideband amplifier but is tuned input and output followed by a low pass filter to reduce harmonic outputs to -60dB or better. It is RF sensed including the unique Spectrum communications monostable RF switching circuit giving fast attack and 500ms hang time to avoid relay chatter when on SSB. The item "50MHz (6m) Linear Amplifier for FT690, 2.5W in 25W out.