Re: FT-243 FUN!

Leland L. Bahr
 

What I would like to know is how Leo Meyerson was able to turn a drill press into a lapping machine.  As mentioned keeping the sides flat and parallel are key.  I could never do it.  Could grind maybe 5 khc with finger and etch around 20 khz.  I read quartz has different density in different areas.  Consequently I think the finger method makes the crystal grind differently in different areas of the crystal.  Good luck for those wanting to try.  The only way I would ever attempt doing it again would be use a lapping machine. 

Lee

/2018 12:50 PM, KD5ALD wrote:

Hello :)
I have done a bit of crystal grinding myself !
Can`t say it is much fun though !
Can take serious time :)
Crystals are ground on a machine !
All a ham can really do is lapping !
or he could chemically etch !
One of the major Crystal manufacturers
Bliley the name was
 devised a method of suspending the finished ground crystal blanks
in a solution of Hydrofloric acid to get the crystals to a very specific and
 accurate frequency !
Neverthless however it is done !
Imperative that the surfaces remain parallel and flat as possible !




On Fri, Dec 21, 2018 at 9:52 AM Paul Goemans <wa9pwp@...> wrote:
Rex,
  A local ham buddy has one of your new X-Checkers, and loves it. He showed it to me, great design. He is a NRR (Novice rig roundup) NRN (Novice Rig Night) operator, so he needs crystals too! 
 
Paul Goemans WA9PWP
Stoughton, WI
 
From: Rex Harper
Sent: Friday, December 21, 2018 9:19 AM
To: main@4sqrp.groups.io
Subject: [4SQRP] FT-243 FUN!
 

4Staters,

Many years ago, I hung out with a couple of pals, Darell WA3OPY & Ron AC5UR, who both worked at ICM. Darell was their crystal engineer and Ron was his right hand man. I was working with QCMs (Quartz Crystal Microbalance) where we slathered bare quartz crystals with a patented glue and stuck compounds on top of the crystal. Then we put it into a holder of my design and pumped water over the crystal face. Specific contaminents in the water would bind to the compounds and change the crystal frequency. We could then determine the contamination level by how fast the frequency changed. That was another life back in the engineering world many moons ago....but it fueled my interest in quartz crystals. Darell, Ron & I hosted a workshop at Ozarkcon in Joplin Mo. where we showed how you can take a 'worthless' 6900+ military surplus FT-243 crystal and grind it to 7030. The 7030 frequency was just recently (at that time) declared a QRP frequency of activity and nobody had any crystals then. I designed a little crystal oscillator and measuring technique for the workshop where we could oscillate & measure the frequency of the quartz slab without having to put it back into the FT-243 holder each time you wanted to check your progress. I seem to remember we had about 35 QRPers all grinding away and every one came out with a working 40m FT-243 crystal...

That whole process was updated and used for my FDIM Buildathon in 2017 but I added a direct display frequency counter to the oscillator to replace the frequency counters we had to round up way back when. That design was recently reviewed by none other than Bob Allison WB1GCM in the ARRL lab and written up in the November issue of QST. All hell broke out and I was kitting & shipping the X-CHECKer kits for 2 months. I finally caught up to the end of the list leaving me little time to much of anything else. Along the way, I redesigned the board one more time to make the kit a little easier to use. So there are lots more hams out there having lots of FUN grinding crystals.

The other point of this email is to let everyone know that I now have a decent supply of brand spanking new FT-243 crystal blanks that make grinding a custom FT-243 for the 40m band a breeze. I would wager that Im the only one in the world silly (or stupid?) enough to track down someone who is silly enough too (to listen to me) and make me FT-243 crystal blanks! I invested an entire SS payment to stock my shelves with another crazy item. These crystals are in the rectangular FT-243 form factor, AT cut and are pre-ground for 7015 +/- 1000ppm which makes them run between 7008 and 7023  so they are already in the 40m band to start. I've ground one successfully up to 7218 so they are easily ground to any 40m QRP frequency of interest. They make putting a vintage rig anywhere on 40m pretty easy. I probably bought too many but I had to in order to get the price down to a reasonable selling price. I have a 3 pack on my parts page for $22 + $3 S&H so you could turn 3 junque FT-243 holders into 3 nice 40m FT-243s on your favorite 40m frequencies for $25.


X-CHECKer kit:    http://qrpme.com/?p=product&id=Q17

Grinding accessories:   http://qrpme.com/?p=product&id=CGA

NS James Millen ceramic FT-243 sockets & crystal blanks:    http://qrpme.com/?p=parts

Wishing everyone a Happy Holiday!

Rex  W1REX


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