[JMS] How does one "grind a crystal" to change its frequency ?
Joe Rubin
srto2007 at hotmail.com
Thu May 31 21:47:50 EDT 2007
Don, thanks for your reply. The way I see it is if you used two (2) large
sheets of glass, with the small blank in the middle, it would act as a pivot
and you would have heck of a time keep them parallel. Of course, I might not
be interpreting the idea correctly... the how could you grind the small
blank between the sheets??? Yes Comet cleaner could be used but it is so
fine that the time to make the frequency change would be long. Sorry, I
don't think many hams have carbon fiber sheets in their junk box. The figure
eight manuever is only a suggestion. It does seem to make sense tho... I'm
thinking that about 2 to 3 kHz is all you could sucessfully move them.
Others may have had better luck than I did. Oil would be much harder to
remove. Part of the success is absolute cleanliness. Oil from your finger
is a no-no. 73 Joe W4CBJ.
>From: Don Buska <dbuska at wi.rr.com>
>Reply-To: The James Millen Society Members Email Reflector
><james_millen_society at mailman.qth.net>
>To: The James Millen Society Members Email Reflector
><james_millen_society at mailman.qth.net>
>CC: Sherrill.Watkins at dgs.virginia.gov
>Subject: Re: [JMS] How does one "grind a crystal" to change its frequency ?
>Date: Thu, 31 May 2007 20:26:41 -0500
>
>Hi Joe,
>
>I was thinking about it. Wouldn't it be better to use two large pieces of
>glass, let say 1 sq ft? If you placed the crystal in the middle between the
>two large glass plates with your grinding solution then one glass could be
>moved in your figure-eight pattern. I would think that simply by the
>relative size of the glass plates to the small crystal it would maintain
>the parallelism.
>
>I remember in my novice day guys would use regular kitchen Comet. I would
>think that whatever abrasive compound you would use that it should maintain
>an even grinding surface and that each grinding particle would be of
>relatively equal size. I could see goofing a crystal up really fast if you
>had more grinding material on one part of the crystal than on another part.
>You would have your non-parllelism simply due to the aforementioned. I
>wonder in this day of hightech composite materials if a solid material with
>a light oil on it surface could be used in place of one of the glass
>sheets. I bet a sheet of smooth carbon fiber is actually a good grinding
>surface for crystals. Now where did I put my stock of carbon fiber sheets,
>hi.
>
>I wonder how they do this work today. I would think that crystal
>development has advanced a long way since the days when hams were doing
>this back in the 40's and 50's.
>
>73
>
>Don N9OO
>
>Joe Rubin wrote:
>>What you need is a small (1" x 1" piece of 1/4" or 3/16" PLATE glass. You
>>can get a piece from your local glass shop for nothing... I was lucky, my
>>father was in the glass business, HI. With this thickness glass, you have
>>some thing "to hold on to"... (the edges). Plate glass is used for it's
>>inability to "bend". The idea is to 'try; to get an 'even' grind. If you
>>use just your finger, you will put more pressure on the center than the
>>edges and ruin the parallelism. Yes, you can ruin one easily without even
>>trying hard... We used to wash the blanks, holding them by the edges...
>>and rubber gloves are a good idea. The surface tension be=tween the small
>>piece of glass and the blank is 'supposed' to hold it... Never had any
>>luck changing them more than a few kilocycles, OOPS I mean a few
>>kiloHertz. You can rinse then off in tap water and then clean them with
>>isopropyl alcohol.
>>Tap water in some areas contain impurities and the slightest bit will keep
>>the thing from oscillating...that is why distilled water is recommended.
>>More info??? 73 Joe W4CBJ/WX4TRA.(Ancient One).
>>
>>
>>>From: john <johnmb at nc.rr.com>
>>>Reply-To: The James Millen Society Members Email Reflector
>>><james_millen_society at mailman.qth.net>
>>>To: The James Millen Society Members Email Reflector
>>><james_millen_society at mailman.qth.net>,james_millen_society at mailman.qth.net
>>>
>>>CC: Sherrill.Watkins at dgs.virginia.gov
>>>Subject: RE: [JMS] How does one "grind a crystal" to change its frequency
>>>?
>>>Date: Thu, 31 May 2007 19:29:17 -0400
>>>
>>>Just a question (and perhaps indicates why I have not been real
>>>successful at moving a crystal very far before activity falls off)... how
>>>do you "figure 8" the thing, without touching it ? They're such small
>>>slivers of quartz, it's really hard to handle it. I suppose rubber gloves
>>>could be used, and only use tweezers to lift it. Cleaning it I guess
>>>could be done in an ultrasonic cleaner.
>>>
>>>The "ancient ones" had a good process, that is not obvious....or....they
>>>too ruined a lot of blanks!
>>>
>>>John K5MO
>>>
>>>
>>>
>>>
>>>At 06:32 PM 5/31/2007, Joe Rubin wrote:
>>>>Dear Sherrill, I used to "grind" crystals in the old days. An FT-243 can
>>>>be taken apart by removing the face screws. Then the crystal blank is
>>>>removed from the holder by slipping it out. The crystal is placed on a
>>>>convenient plate glass square (about 4"x4") size irrelevant and a small
>>>>amount fine of carborundum powder (you can use automobile valve grindind
>>>>compound, the fine stuff only and 1/4" to 3/16"r the blank and usually
>>>>rotated in a figure eight or so. The idea iis to use very light pressure
>>>>and keep the faces paralllel . A few 8 and the blank is washed very
>>>>carefully , reassembled and tested on an oscillator or the intended xtal
>>>>circuit. It is not a fool-proof method and often the thing will quit
>>>>working a you cannot get it to oscillate again. The reasons vary but
>>>>usually due to lack of parallism sm, or lack of cleanliness. The blank
>>>>should be handed by the edges only. The crystal an only be moved so far
>>>>(a few Kc) and if one is out of the amateur band I doubt it could be
>>>>moved very far.
>>>>Crystals oscillate in the fundamental mode, that is if you have one for
>>>>forty meters (7 mHz) it will oscillate there. An overtone crystals
>>>>manufactured to perate in the second to fifth harmonic (7 x 2 = 14) (7 x
>>>>3 = 21) ... of course there are special cases. The older Amateur Radio
>>>>Handbooks used to have articles on this subject. I will try find some
>>>>for you. The main thigs to remember are: paralellism, Cleanliness and a
>>>>limit to the frequency excursion.. Let me know if you need more
>>>>information or futher explanation.... 73 Joe W4CBJ/WX4TRA.
>>>>
>>>>>From: "Sherrill Watkins" <Sherrill.Watkins at dgs.virginia.gov>
>>>>>Reply-To: The James Millen Society Members Email Reflector
>>>>><james_millen_society at mailman.qth.net>
>>>>>To: "The James Millen Society Members Email Reflector"
>>>>><james_millen_society at mailman.qth.net>
>>>>>Subject: [JMS] How does one "grind a crystal" to change its frequency ?
>>>>>Date: Thu, 31 May 2007 10:27:47 -0400
>>>>>
>>>>>Friends and Members of the James Millen Society: Please be advised that
>>>>>from
>>>>>time to time, I see FT-243 crystals for sale in odd frequencies; i.e.
>>>>>that
>>>>>are outside of the amateur bands and of no use. Years ago, I heard that
>>>>>it
>>>>>was possible to "grind" a crystal to raise its frequency. Also, I heard
>>>>>that
>>>>>one could "rub" a crystal with pensel graphite to lower its frequency.
>>>>>Yet,
>>>>>I have never seen any article published in any major amateur
>>>>>publication
>>>>>including various handbooks, or magazines such as QST, Electric Radio,
>>>>>The
>>>>>Old Timers Bulletin, etc. as to how this process is be performed. Can
>>>>>anyone
>>>>>refer me to a good source or explain the process in great detail? Also,
>>>>>what
>>>>>is meant by the term, "overtone" crystal? Thank you very much. -
>>>>>Sherrill W.
>>>>>k4own, member
>>>>>______________________________________________________________
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>>>>>Post: mailto:James_Millen_Society at mailman.qth.net
>>>>
>>>>_________________________________________________________________
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>>>
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>>
>>_________________________________________________________________
>>Don’t miss your chance to WIN $10,000 and other great prizes from
>>Microsoft Office Live
>>http://clk.atdmt.com/MRT/go/aub0540003042mrt/direct/01/
>>
>>______________________________________________________________
>>James_Millen_Society mailing list
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>
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