[Milsurplus] BC-659 Fun and Games and now the EF50

[Ray Fantini]

AI Told me the Sylvania interduce Loctals in 1939.  Don't know when RCA brought out the seven pin tube but can see where the seven-pin tube is better in terms of size.  I have a Philips EF50 tube that I have been told was interduce in 1938 that looks like a loctal to me that was used in the WS-19, legend has it that the tube was some sort of secret weapon and smuggled out of Holland and critical to British Radar sets?  Wiki tells me that Prof. Dr. Jonker was working on developing the tube in 1934/35 way before Sylvania and has a good description of how it works in terms of removal.
I have a EF50 on my desk in the shop just to look at.
You can read the Wiki thing about the EF50 at:

https://en.wikipedia.org/wiki/EF50

If maybe Sylvania/Philips had a patten on the base structure maybe RCA was reluctant to deal with them and just out produced that technology until it was dead? Don't know myself but you see way more Octal, seven and later nine pins used then loctals. By a factor of at least twenty to one hundred to one.

Ray F/KA3EKH






________________________________
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> on behalf of Jim Whartenby via Milsurplus <milsurplus at mailman.qth.net>
Sent: Monday, July 6, 2026 2:46 PM
To: milsurplus at mailman.qth.net <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] BC-659 Fun and Games

Loctal tubes used the "button base" to hold the tube elements so they were inside the glass envelope vacuum.  I believe that they were released at about the same time as RCA released the seven pin miniature tube design which are physically much smaller but also use the "button base" concept.  I guess that it was market forces that chose the subminiature tubes over loctals for new designs.
Jim

Logic is a systematic method of coming to the wrong conclusion with confidence.  Murphy


On Monday, July 6, 2026 at 12:50:02 PM CDT, Ray Fantini via Milsurplus <milsurplus at mailman.qth.net> wrote:


Wow man, it's amazing what you people know. Never knew any of this about the loctal and now got to try that. Maybe because of the difficulty in dealing with the sockets they never caught on?
Between dealing with these weird tubes and now knowing what all those countless boxes of crystal sets were for with the cryptic three-digit numbers were used in I think I learned a lot from dealing with this old 659. Waiting for parts to compleat repairs of the power supply and hope to get this set up and running soon, had the receiver running with substitute components for testing and it's not that bad going full quieting at around 10 to 13 uV and useable down at around 3 uV with a big fat IF passband but figuring if it had to work with things like the BC-1000 (SCR-300) it has to be capable of about 30 kHz so think netting with more modern sets like the PRC-25 or VRC-12 won't be that big an issue. Finding a legal frequency may be more of a problem. Think the VRC-12 stuff may go down to 29.6 as a Red Flag channel?  Will have to go out to the mutt and crank on the RT-524, maybe once I get this all resolved can do a video of a BC-659 in a GPW having a QSO with the VRC-12 in the mutt?

Ray F/KA3EKH



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