You can see quite a few here:
Originally Posted by K5UOS
I know of at least two hollow-state direct-conversion receivers in QST:
May, 1961 (more than 50 years ago!) W2WBI described a "T.R.F. Receiver" for 80 and 40 with a balanced detector. RF stage, pair of pentagrids, VFO, audio amp. Nice job, but for that many tubes you could have a small band-imaging superhet. Although the term "direct conversion" is not used in the article, it is clearly that kind of receiver.
July, 1973, shows "The 80 Meter Pebble Pulverizer" by W1CER and W1NPG. A complete QRP CW transceiver for 80 using tubes. 6GX6 is the detector.
73 de Jim, N2EY
Originally Posted by N2EY
I subscribe to the HBR site and the email reflector, too. It is a fine site for anyone interested in researching tube receiver design. Kee's has most of the HBR circuits available for download.
I also remember your tuning mechanism made with a bowl.
That said, I would not build a tube receiver based on the HBR series for obvious reasons. It is not a very good performer above 40 and 80M.
But I have used circuits like the audio stages and IF stages from the HBR. The HBR14 is a good candidate for a DDS (like Pat, WA6MHZ is designing) but the RX's still need improvement in selectivity.
I knew there were other DC tube receivers. There are some others on the web and I know we have discussed ideas about them on the glowbugs site.
But Galen, WB0RIO, has a unique design, all his own. It is pretty cool! There are not many folks scratch building tube receivers (or any type receiver) and a unique design is nice to see.
There were reasons the tube DC receiver didn't catch on. You mention one above. For all the work you could build a really great entry level superhet. There are lots of other caveats.
Since effectively all the gain is at audio (often > 100dB) the difficulty increases in tubes over solid state.
I like pointing out your station: It is unique, too. Tubes are fun.
My (older) brother and i built the pebble pulverizer ( thats actually a stretch, he did most of it, i just made a mess) i do remember that the thing was really prone to microphonics (an understatment) and common mode overload, wls came in like gangbusters everywhere and all of the time. And the selectivity was pretty bad. The regen he built didn't suffer from any of that stuff.... at least not as badly anyway.
40 years later i've forgotten all of that and think that a tube DC rx is a good idea.
That's really cool. I LOVE the cabinets!
Originally Posted by WB0RIO
"A minute of measurement trumps a decade of debate."
I second Erics statement Galen, very clever use of the electrical boxes as chassis. I'm curious, why a DC receiver and not a regen?
I'm sorry you don't have the experience or understanding to realize that others possess a skill set that you seem to dismiss as fantastical.