Hello and welcome,
The galaxyhf.pdf file (download) is a review article by w2aef, of the Galaxy 2000+ HF Amateur Linear Amplifier found in a 1967 issue of CQ Magazine. While this amplifier never really caught on in the amateur radio market place, the circuit has some interesting items covered in the review. The file download are Adobe PDF copies of the gif format pictures you see on this description page.
The amplifier is a classic sweep tube circuit, using ten 6HF5 beam power tubes in parallel. Pretty close to a record in the real Amateur Radio (not CB) amplifier market!
Amplifier Builders often question the practical application of so many small tubes vs. one or two larger tubes, but that's not why I put the article up here. There's a very interesting Linearity Control section described and shown on the second page. The control grid bias is "shifted toward operation in the Class-A Region, ...when non linearity tends to occur." I get real nervous around dynamic bias circuits like these in classic tube amplifier applications, but the design of this circuit is worth study and it has other uses. The Collins Brand of HF Amplifiers contain a center tune meter indication using a similar circuit. I'll keep my control grid bias potentials constant for now thank you, but a linearity indication (meter?) would be a very interesting addition to your amplifier project.
Another point of interest is the capacitive voltage divider tank circuit. Used to deal with the typical low output impedance of sweep tube amplifiers, it's also described in some detail. So, if you were around in 1967 and thumbing through a CQ Magazine to these pages... would you have been impressed enough to buy the amplifier? Alas, Galaxy Electronics fell by the wayside some time later as did World Radio Labs; both were found in Council Bluffs, Iowa.
Enjoy the article
Cheers,
Skipp
enjoy
skipp
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