G4AKW

The specification and base pin out left is for an 813 Power Pentode in class C. Photos of my twin 813 amp are shown below. Its little brother amplifier shown is a 3 x 807 beam tetrode HF power amplifier which has evolved over the last couple of decades. In fact I'm pretty sure that one of the three 807 valves is out of my first transmitter, a No 19 set, purchased from G3WQN in 1970. Output power is about 150 watts on 160m, 80 and 40m. The 813 linear is currently configured as per G2DAF design with step up and rectified input for the screen supply. One pic shows the 813 beam power pentodes next to a 5u4 rectifier - for size comparison. Between 2kV and 2.5kV is needed on the anode and 400V for grid 2. The pentode construction gives very high gain and in class C (CW) 4 watts input should result in nearly 400W output (each). (ICAS conditions - not current bias cndx). So one in a box could be a nice add on to the FT 817ND. .

The first photo shows the two 1u shelves of the transverter sitting on top of the h/b 3u 80m qrp (3 w) cw tx/rx. The transverting (mixing) functions were turned off and the only modules used from the transverter were the Norton broadband receive amplifier and the linear amplifier. The linear produces 170 watts output on 80m (it gave 130 watts on 20m) and the next picture shows the linear amplifier splitter, high power combiner, 2 x dual Mosfet amplifiers and dual switch mode power supplies. The third photo shows a close-up of the 170 watt combiner and the input circuit of one the linear amplifiers. The 4 x IRF510 mosfets have proved very reliable (at a lower power level). The antenna (capable of handling up to 3 amps peak) and an 80m dipole was built using 300 ohm ribbon with the two conductors connected together. The 4th photo shows the dipole centre piece made from a chopping board. The DC rx in the QRP rig makes it difficult to copy cw in any but the best conditions for a DC rece...