Here are some pictures of my GS35b amplifier for 6 meters I built back in 2005. 90W drive delivers about 1500W output. This amplifier was designed to run 24/7 key down for heavy contesting and high duty cycle WSJT modes. The output network is a Pi-L to suppress the second harmonic and a T-network is used for the input. I based it on K8CU’s 6m amplifier and pulled some ideas from other places like the ND2X QRO site. It was very easy to build using a drill press and hand shears. Cutting metal was 90% of the work. There are a lot of pictures on this page. Please allow time for them to load.
This is not a SMALL amplifier! It’s built for continuous duty.
plate transformer is a Peter Dahl unit rated for 2750VAC at 1.5A
Control logic is from the triode control board. The HV supply cannot turn on until the filament has been on for three minutes. After the time has expired, the control circuit turns on the HV supply.
strap and screws are used for the anode connections. A Teflon chimney not shown
here is held in place with a hose clamp. Layout was not critical since a lot of
room was available. Connections were made as short as possible. The
Tuned Input Setup Notes
Setting up the tuned input without powering up the amplifier is easy. With the tube in the socket, solder a temporary 110 ohm non-inductive resistor with an 18pF capacitor in parallel to the tab where the input connects to the tube cathode. Hold the other end to ground. Hook up a MFJ 259 analyzer or equivalent to the input. Adjust the input variable capacitor and squeeze/spread the inductors to obtain a 1.1:1 VSWR. This should not be a sharp dip. Remove the temporary resistor. The input impedance of the tube is higher on 50MHz than the published value of 35 ohms for an HF amplifier.. It’s closer to 90-100 ohms. This may take some experimentation to get it right.
Plate Voltage 3800V
Plate Current 850mA
Grid Current 260mA
Idle Current 150mA
Inside the Anode Compartment
Bottom of the RF Deck showing the G3SEK Triode Board and Tuned Input Box
Inside the tuned input enclosure. The filament choke is near the bottom.
Another view of the bottom showing input cover in place and HV wiring attached
Close up of the G3SEK triode board and associated wiring