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Author Topic: Crystal use in the Heathkit DX20 transmitter.  (Read 458 times)

K9ZPU

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Crystal use in the Heathkit DX20 transmitter.
« on: January 22, 2022, 01:59:05 PM »

Can the modern miniature xtals (now placed in FT243 holders) stand up under the crystal currents developed in the DX20 oscillator circuit? On 20 meters and above, when using a 40 meter miniature, the grid drive rises then drops very quickly and the 6cl6 plate turns red after short keydown.

Any opinions, ideas, etc. about what might be going on?
Thanks!
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K4HPP

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Re: Crystal use in the Heathkit DX20 transmitter.
« Reply #1 on: January 22, 2022, 07:27:53 PM »

I still have my 1959 novice DX20. Never had any luck at all with "repackaged" modern day crystals. The ones that work at all cause serious chirp. If you are lucky, you may be able to find some real FT-243 crystals on eBay from time to time. I've managed to collect 15 or so over the past few years. All of them from 7.005 to 7.060. Great for SKN on 40 and 20 meters.
Best of luck.
Jim - K4HPP
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VE3WI

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Re: Crystal use in the Heathkit DX20 transmitter.
« Reply #2 on: January 24, 2022, 12:54:36 PM »

Earl VE3AB has a big list of crystals for sale on his website.  You might find useful ones there.

http://nettyelectronics.com/

73
Dave, VE3WI
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K3STX

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Re: Crystal use in the Heathkit DX20 transmitter.
« Reply #3 on: January 27, 2022, 06:26:08 PM »

I have found those little "QRP" crystals in the FT-243 holders chirp like crazy. Real FT-243 crystals are all over eBay, I have had great luck getting them there.

Paul
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K4PF

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Re: Crystal use in the Heathkit DX20 transmitter.
« Reply #4 on: January 29, 2022, 09:31:15 PM »


You might consider making an adapter out of a bad FT-243 crystal's holder,
with an HC-6/U socket mounted on one end. 
HC-6/U crystals may be more common than FT-243 type these days.
The Heath DX-60 series had a socket included for the HC-6/U, so that crystal type should stand a transmitter oscillator's rf current without chirping.

I picked up a home-brew adapter with the HC-6/U socket hanging off the end
of an FT-243 holder, just supported by the miniature coax soldered to it.
It was a five-minute project for someone.  It works fine.

73,
Ed Knobloch
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N1MG

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Re: Crystal use in the Heathkit DX20 transmitter.
« Reply #5 on: February 03, 2022, 04:00:31 AM »

Another approach is to build a two transistor crystal oscillator and buffer for the tiny crystals.  Then use that like you would a VFO to feed the DX 20.
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N2EY

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Re: Crystal use in the Heathkit DX20 transmitter.
« Reply #6 on: February 08, 2022, 07:51:22 AM »

Can the modern miniature xtals (now placed in FT243 holders) stand up under the crystal currents developed in the DX20 oscillator circuit? On 20 meters and above, when using a 40 meter miniature, the grid drive rises then drops very quickly and the 6cl6 plate turns red after short keydown.

Any opinions, ideas, etc. about what might be going on?

The 6CL6 plate turns red because the crystal isn't oscillating. So you can't use them in the DX-20.

Those "restuffs" don't work in most vintage transmitters because they're not designed for the crystal currents vintage transmitters use.

Your best bet is to buy/build/restore a suitable vintage VFO, and/or get some "real" FT-243s.

73 de Jim, N2EY
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