Sunday, January 29, 2012

MY QSL-40, FOUND!

My QSL-40 has been found for awhile but I've only recently had time -- and light -- enough to photograph it:Front view (tomcat left in for scale). The 40m coil is installed.

Under chassis view (tomcat as per above) -- the chewed-up resistor is a 100 mA shunt across the (actually) 1 mA/1V/1k meter. You didn't really think it was a 4-Ampere meter, did you? It's salvaged from an old commercial rig. If you look carefully, you can see the insulator the 140 pF variable is mounted on.
Close-up of the front. The crystal is one of a batch I purchased from Phoenix Crystals, which was one of the very last of the small crystal grinders. Sadly, the owner passed away about ten years ago and no buyer could be found for the business.

Changes from the original Fred Sutter transmitter are few:

1. I used a male chassis connector for the power supply. --These days, I'd use an octal, as the "tube base" pattern 4, 5, 6 and 7-prong plugs (though not tube sockets) are no longer made.

2. The crystal is an FT-243 rather than a "doorknob" type and the socket is according different. You could use a 2-prong socket for the crystal if you had one, but they'll fit an octal tube socket okay. (There's a no-wrong-way-to-plug-in wiring pattern for FT-243's in an octal socket. I didn't use it but I'll look it up and post it if any reader is curious.)

3. I should have used enameled wire for the coils. What I did use is #14 house-wire, stripped. This increases the hazard, since the coil is at B+ potential. (Now that I own a drill press, I can redo them properly.) The material holding them is clear plastic rather than black Bakelite. --But that is real Duco glue holding it all together!

4. The meter is different, a square one instead of the round version he used (probably a Triplett and a bit nicer than the Readrite typical of low-end designs at the time). It was the right size and I had several.

14 comments:

  1. My first transmitter was a 6C4 oscillator driving a 6L6. I could get about 25 Watts out to the antenna "on a good day". I only used it until Christmas because my Dad bought me a DX-60, but I kept it around for years.

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  2. Very nice Roberta! Fred Sutter had some neat designs. Glad to see some new posts from you, was afraid you had fizzled out.

    73, Steve W0GSQ

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  3. There's gotta be a crack about "cat whiskers" in here somewhere...

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  4. Somewhere, maybe, I have the 6V6 transmitter I built from probably the Handbook long before I got my ticket.

    Of course I was young and immortal then, so B+ was 220V mains via a bridge rectifier. Yea, I know.

    At least I didn't use it much, not knowing the code or having a license at the time...

    I recently got a whole bunch of goodies of the vacuum state variety, figure I should also build a few retro-antiques. They're gorgeous.

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  5. I presume the No. 47 is (also) for tuning?
    Love the real crystal!
    Somewhere on the web must still be instructions for grinding your own. That'd be an interesting process.
    Sign: Kitty learns curiosity bites back.

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  6. Nice to see you posting again!

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  7. Ed S.

    I remember tweaking the frequency of FT 243's by marking them with a pencil (lower) or grinding just a tad (increase). Never ground one from scratch though.

    And here is a web page I just found by W8TIF on grinding. He even mentions the pencil trick.

    http://www.electronics-tutorials.com/oscillators/crystal-grinding.htm


    Terry
    WA4AMG

    Putting the Old in OM.

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  8. I hadn't fizzled, just too darned busy to post.

    The pilot light is in series with the crystal -- something of a fuse.

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  9. A one cubit, 16 pound cat "for scale"?

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  10. I didn't say *what* scale, did I? ;)

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  11. The bulb's filament has a negative temperature coefficient. As the current increases (and the temperature rises due to the resultant heating), resistance increases thereby limiting the power and, in the circuit, protecting the crystal. (Had to dig in the old books for that one!)

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  12. Roberta, where do you find the nice ceramic stand-off insulators? I'm building a BALUN box to replace the late, lamented, stolen Russian Kite and I had a heckuva time finding the standoffs.

    rcnixon(at)mindspring(dot)com

    Russ - kf4wxd

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  13. I picked those up at MAI/Prime Parts in Indy -- might be worth asking them.

    Ceramic parts are one of the things I always look for at hamfests. It's worth keeping some on hand, just in case.

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  14. That pilot light acted as both a regulator/ fuse, and warning to lay off the Key, according to Sutter. Heh, keep yer dah's short! The idea was to keep that light lit as little as possible. But then, you could do those electronic gymnastics with a Bliley Door Knob.

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