Re: [QRP-L] Plate Glass for Grinding Crystals


Rex Harper
 

Gangue,

Indeed, WA3OPY, Darell Brehm, and AC6UR, Ron Hall my buddies at International Crystal Manufacturing and W1REX (me) gave a crystal grinding workshop some years back at Ozarkcon when it was held in Joplin Mo. I designed a pretty nifty rig for measuring the crystal frequency between grinding steps and put together the materials for the workshop. The hardest thing was finding enough out of band crystals in a frequency range close enough to grind into a useful QRP frequency. I bought hundreds of FT243 crystals in order to get enough 6975Khz crystals for the workshop. I modified a standard crystal testing circuit to test the blanks outside the FT243 holder with enough 'anticipation precision' so that when they were re-installed into the FT243 holders, you got what you wanted! A good time was had by all and (almost?) everybody went home with a FT243-7030 hand made crystal!

The crystal (under construction) tester was the basis of my Build-Along presentation at FDIM a couple of years ago and still appears on my QRPme kits roster as I still have a few left. I did contract a local commercial glass shop to make me DOZENS of 6"x6" plate glass grinding platforms.....and we did use Bon Ami a very fine grit cleaning compound (like Comet) that the old timers used and you can still buy in your local supermarket. I do have a small supply of cut & beveled edge grinding plates left which I will part with for $10 each...

For this years FDIM Buildathon, I presented the Beaconator which was a simple 30m beacon transmitter that could also be used as a straight transmitter. I used a Picokeyer chip from Ham Gadgets to enable both options. I wanted each beacon owner to have a unique frequency but didn't have the time to have everyone grind a crystal....so I took the other old-timer's approach. I had a batch of HC-49 30m crystals made at the QRP area but had the crystalls delivered in UNSOLDERED HC-49 cases . So the builders simply removed the rubber band and 'penned' the crystals down in frequency using a pencil. I have leftover Beaconator kits and cheap deals on just the board & crystal on my QRPme website too!

So if you are looking to have some fun playing around with beacon transmitters and messing with the internals of quartz crystals, I have some fun kits you might be interested in.....

Rex
W1REX

On 7/8/2013 10:56 PM, L L bahr wrote:
I am again going to try and grind some crystals and need a piece of flat plate glass maybe 1/4 to 1/2 inch thick to try and do it. I don't know if all plate glass is flat or if some is better then others. I'm not sure where to get it and would suspect something like 6 inches to 12 inches square would work just fine. I have not checked out some local glass shop and maybe this is where I should go. Is there anyone on here with any good suggestions as to what I need and where I could find the appropriate glass?

Thanks,

Lee, w0vt

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