Universal triode input board

To build another tube amplifier, I needed a matching to the 50 Ohm output of my solid state transceiver. It had to be universal and applicable in a normal tube amplifier. I did not bother do make it perfect on the first attempt. It should be easy to experiment with variable mica capacitors and any form of inductor, on a toroid or an air inductor. If a good match is found the mica compression trimmers can be replaced by fixed capacitors mica / ATC100B or whatever.

The schematic can be seen below:


Note that there are no capacitors in the circuit, those capacitor values should be set experimentally. There are 6 bands and one loop-through.

For initial testing there is a loop-through (the most left in the circuit diagram), this enables me to test the output and use my antenna tuner as a temporary match on the input.

As relays I use most of the times the Fujitsu FTR K1CK012W relay. The relay has proven to be very sturdy. These relays are very affordable and reliable For €1,75 it is hard to find a better one. The datasheet is HERE :  ftr-k1

The board is double sided and designed in a way the the RF part is on the top and the DC part is on the bottom. As much as possible ground-plane is on both sides. Connected with uncountable vias to provide good grounding. The top section has no solder mask, this ensures easy experimentation.

The board is 15 x 15 cm in size. If you are interested in this board you can ask if I have some boards left.



A friend of mine saw this page and informed me about the W7DS website. He offers a similar board a bit smaller than mine and without the direct connection to the input. He has a manual with some suggestions for values of the matching components for several amplifiers. He did a lot of work to sort that out. He also offers complete kits. A link is HERE