I have built a couple of amplifiers mainly for the VHF-UHF. The largest project was the famous W6PO 8877 amplifier. However I sold that amp many years ago.
K2RIW/W2GN's stripline kw for 2m is an other amp I made that has been working well and still is.
Eimac tubes are good however also expensive. Russian tubes like the GS-31b, GS-35b, GU-74b or GI-7b are much more value for the money. However the GU74 has moved to the west due to ACOM (ACOM-1000) and other amplifiers (Alpha91B) and are not seen cheap anymore.
Link to an ongoing projectwww.sm6why.n.nu/ldmos-hf-pa
Links to other ongoing PA projects
. Water Cooled 23cm Pa www.sm6why.n.nu/water-cooled-23cm-amp
. HV on wheels www.sm6why.n.nu/HV-on-wheel
. Future projects www.sm6why.n.nu/future-projects
This amp is built by an Ukrainian radio amateur (Alex). I have done some "face lift"
Here some face lift done.
Testning the amp on 20M 600W to a dummy load. Also looking at the spectrum which looks clean. 10W of drive about 450mA Ia and 2.3kV Ua. 1kW input which means about 60% efficiency. The meter will also be replaced later.
I replaced the meter and custom made a new scale.
The scale is made with GALVA, a free software.
On the Air test.
First I put out 10W and bypass the Amp and look at the spectrum analyzer.
10W to the antenna tuner is equal to -44db on the SA.
100W is -34 db. Make sense, should be 10db gain.
PA on generates -26db. Which also makes sence, 100W to 650W is about 8db. This means that the the power meter on my antenna tuner is accurate compared to the spectrun analyzer.
This is how a W6PO design looks like. This one built by 9Q1EK, in mine was all parts silver plated.
70cm Pre Amp (3SK97)
2m Pre Amp (3SK97)