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Sunday, November 21, 2021

KG7TR's Magnificent 75S-2B Receiver -- Tubes, an Si5351, an Arduino, a Bit of Collins, and a Bit of a Drake 2-B


Oh man, I share this with much trepidation because the last time I posted something about the work of Mike KG7TR,  Pete N6QW said he felt like putting all of his own work in the dumpster, so much better was the artistry of KG7TR.  This receiver is so cool and so well-done that we now  might have to post a guard outside the N6QW shack -- heck Mike even has an Arduino Uno and an Si5351 in there!  Don't do it Pete!

I was led to this magnificent receiver by the very humble 6U8 tube.  Scott  WA9WFA and I have been learning (mostly from Grayson KJ7UM) that the much used and sometimes loved 6U8s (three of them in our "Mates for the Mighty Midget")  might be a bit long in the tooth, old even by Thermatron standards.  I was worried when I remembered that my Drake 2-B has a 6U8 in it -- V2, the first mixer.   So I Googled for more info and was led to this amazing receiver, a 2018 creation by KG7TR.  How did we NOT see this for almost four years?

Here is more info and pictures: 


Here is Mike's write-up of the project: 


Mike KG7TR's web site:


As for the 6U8s, well Grayson says the tube has been getting something of a bum rap.  And  KG7TR has two of them in this receiver, so I will obviously have to give the 6U8 another chance.  


I didn't know that Lew McCoy had his own crystal and crystal filter company: 



  1. Mike built this awhile back and 1st published it in Electric Radio. Actually I think you commented on it before. Mike is truly a "master homebrewer". His stuff is always a pleasure to drewel over. He swears he only uses a hack-saw and files. No power tools, CNC, etc. It always looks professional.
    I remember the filters, but had no idea the company was created by Lew McCoy. Wish I could find one of those filter packages!

  2. This has to be wishful thinking. I never saw anything connecting the two McCoys, and a serch now turns up his obituary but no mention.

    Lew McCoy started work at the ARRL in 1949. How does that explain a company started in 1952 in PA? He originally had a W9 callsign, so it's not likely even family in PA started the company with his help. If there'd been a connection, surely more McCoy filters in ARRL publications; instead, KVG was almost the house brand.

    McCoy Electronics was a subsidiary of another company, not sure when that happened.

    McCoy was an early source of HF crystal filters, at least for hobbyists. I can't remember when they were first available, but they were on the cover of 73 in 1968.

  3. Michael: I think you are right. I remember Lew wrote a series of memoir articles for Electric Radio -- I don't remember him mentioning a crystal company. Also, Google shows the founder of the crystal company as Luther McCoy. Close, but not the real McCoy, right? 73 Bill


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