[Milsurplus] Crystals new and old

[Ken]

Charlie: I have had much the same thoughts as you on this problem.In my case, I finally settled on the idea of buying FT-243 crystals which were below ham band frequencies, and then grinding or (preferably) etching them up to a chosen frequency by using some sort of low % solution containing HF.The easiest and cheapest HF-containing solution that I, and others here, have found to work acceptably and safely (enough), is Whink Rust Remover, found in the household cleaning supplies section in most supermarkets.Of course, even at 1% HF, one must be extremely careful how one uses the stuff, but it does work, although slowly.Its BIG advantage over grinding is that it leaves the crystal very clean.The process is very time-consuming.There is also a solution containg HF sold in art supply stores which is used to etch designs on glass. I believe it is 5% HF.I have not yet used that, however.Pure or "high grade" HF is EXTREMELY dangerous and IMHO, should NEVER be used by amateurs.Ken W7EKBSent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
-------- Original message --------From: CL in NC via Milsurplus <milsurplus at mailman.qth.net> Date: 8/8/24  08:07  (GMT-08:00) To: Milsurplus <milsurplus at mailman.qth.net> Subject: [Milsurplus] Crystals new and old When ICM went out of biz, I was pretty ticked, but I guess the technology evolved making the need for a lot of crystals and their sales fall off greatly.  But, what happened to all the equipment ICM used, did someone buy it to scrap it?  I had hoped a cottage industry would have opened up.  So, I decided to start figuring out what it would take to roll my own.  A couple 1934 QST's had articles showing how to make your own, even the design of a copper cutting wheel saw to make slices, one article had the only place I have ever seen the formula for how thick the first cut needed to be in order to get to a particular freq, plus also gave the angles of overtone crystals and how to sight through the Brazilian quartz(preferred) to see where to cut.  I bought a couple small pieces of surplus gear needed to check crystals, and in the manual of one of them was a typewritten set of instructions from within the Midland Company.  In it, it detailed a procedure for the night shift on how  to make crystals, seal the metal cases, HC49's I think, offsets to compensate for freq changes between ground crystal and finished, all this was done in house by Midland, who at that time, was a big CB radio builder, making their own crystals.  The process must have evolved quite a bit in the early 60's such that even a CB maker had a line to make their rocks, just wished the machines had survived.As a caveat, one fellow mentioned putting smaller crystals in FT243 holders.  AF4K did that, and had complaints about burned out crystals when they were used in a rig wanting high crystal current, like homebrew transmitters or the Conar 400.Charlie, W4MEC in NC______________________________________________________________Milsurplus mailing listHome: http://mailman.qth.net/mailman/listinfo/milsurplusHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:Milsurplus at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html
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