HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: JimIO on June 25, 2018, 0309 UTC
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Will an HC-49S crystal work in a tube rig?
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Probably.
I think one or 2 of my crystals are HC 49. Not sure about the 495 though.
One way of finding out.........
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Will work in any radio, it's a Xtal, a passive like a capacitor...
Str.
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Reason I ask is I just got a Heathkit DX-35. The original power transformer had been replaced and it was a real rats nest. I've ripped out all of the non original parts and will build an external power supply/modulator for it. I only have some HC-49S crystals for testing now. I see they are rated 100uW drive (whatever that means) and I don't have any data on the old style crystals. When I'm ready to test it I will see what happens and post it here.
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You can put a resistor in series to limit the current if needed.
Check for circuits in th'Net.
Str.
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Typical protection scheme of the day was a miniature bulb in series with the crystal.
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I just bought a half dozen FT-243 crystals in the 6.3-6.5 Mhz area. Going to try crystal grinding.
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Be careful. Even a few strokes on what seems to be a well oiled fine grained whetstone can send those things off the chart. I was fool enough to try it as was a guy I knew. At least they were cheap then? Some people use toothpaste and mineral oil with success, but it's time consuming.
I'd blame the whetstone thing on youth, but we were both past forty. Live and learn.
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You can fine tune xtals by lightly using a lead pencil on the faces, but that can only lower the freq a bit.