EDIT: inserted original text below.
To: Multiple recipients of list From:
firstname.lastname@example.org (Paul Carreiro) Subject: Help in FT-243 Grinding
Greetings fellow boatanchorites!
I need help from all the BA gurus out there practiced in the
mysterious art of grinding FT-243 type surplus crystals to operate in
the ham bands.
I have had some success bringing crystals down in the 6.8 to 6.9 MHz
range up into the 40 meter band using dry "ultra fine" grade
sandpaper. Some have resulted in fine CW tones, others seem to be
chirpy and have rather lousy short term stability as the transmitter
is keyed ( <1/2 second of instability). I realize this instability is
a characteristic sound of the era, but some of these crystals seem to
be overly unstable and are just about unusable for CW work.
So, I'd like to call on the collective experience of all you OTs out
there, to help pass on this magical, little understood, and quite
possibly lost art of grinding surplus FT-243 type crystals into the
ham bands. What were all the tricks of the trade back then? Are
there any new fangled products on the market that would make this task
easier or more accurate?
I also have some general questions on the subject: Is there a limit
in how far you can change the frequency of a crystal? Seems my
attempts at bringing crystals up from 6.7 MHz and below up into the
7.0 MHz range have all resulted in very chirpy output signals.
I've heard that you can alter the frequency slightly up or down by
changing the spring tension inside the crystal. If so, does more
tension lower or increase the frequency?
What's the best trick to keep from overshooting your desired
Also, is there a frequency or section in the 40 meter band that is the
hang out for Vintage/Classic gear?
Incase you're curious, I'm using these crystals in Johnson Viking
Valiant, WRL Globe Chief 90A and Allied Knight T60 transmitters.
Thanks in advance for any and all help! 73 from a young pup trying to
get the old dogs to teach me some new tricks.
Paul, N6HCS email@example.com
From: "Hal R. Waite" Subject: Re: Help in FT-243
Try tooth paste or better yet tooth powder in a heavy water slurry
on a glass plate. Using light pressure from the second finger (the
one that is used for signaling) and a circular motion, grind each of
the straight outer edges lightly. Then clean off and dry. If you
overshoot, a small amount of pencil lead rubbed on the center of the
crystal face will either lower the frequency or cause it to fail to
This takes a light touch and a bit of practice. Avoid grinding the
center of the crystal face.
Hal K4GFI/7 firstname.lastname@example.org
From: "Roberta J. Barmore" Subject: Re: Help in
Hi! [Fair warning--most of what I'm going to say is hearsay, culled
from old magazines rather than actual experience. At least one fellow
who posts to the list has ground his own xtals from scratch, and I'm
hoping he'll have additional comment--oh, Gordon???]
On Fri, 4 Aug 1995, Paul Carreiro wrote:
I have had some success bringing crystals down in the 6.8 to 6.9 MHz range
up into the 40 meter band using dry "ultra fine" grade sandpaper. Some have
resulted in fine CW tones, others seem to be chirpy. [...etc. ...]
Based on what I've read, any grade of sandpaper is too
rough--scouring power for big jumps, toothpaste for small ones & final
grinding on the larger changes. You can also get grinding paste in
various grades at hardware stores, though most of what I see is in a
waxy base for buffing-wheel work. You've got to keep both of the
large surfaces parallel and flat! Work on a slab of plate glass (try
junk shops, glass stores, and/or any telescope hobbyists you
know--don't take a used lens grinding glass, though, it's not flat any
more), and for small rocks, consider grinding a bit of thick brass
flat and using it to push on the crystal with. If it goes inactive,
grind gently at the corners. Cleanliness is vital. before putting
it back in the holder, wash your hands, rinse the crystal; set it down
on a clean and soft surface, wash your hands again, put on gloves
and clean it with something that'll zap any oil, like 1,1,1
trichlorethane ("Carbo-clor") or possibly denatured alchol. (With
older rocks, "cleaning the crystal" was a regular thing). Wash your
hands before you start, too, and don't touch your face or hair while
thinking what to do. (A dab of denatuared or trichlor will de-oil
your hands, though it doesn't do the skin any good [yessiree, that's
why I'm a hand model now, ha!] and may be hazardous--EPA and kin
aren't very keen about trichlor). B
I've heard that you can alter the frequency slightly up or down by
changing the spring tension inside the crystal. If so, does more tension
lower or increase the frequency?
More tension, higher freq--within limits! Saw mention of this and
other tricks, like adding a shunt trimmer condenser, in an old CQ just
the other day. (Naturally I can't find it now). The article mostly
concerned making 'em tweakable--the best trick was an FT-243 version
of the old vari-gap "rubber crystals," for which purpose it was
suggested the best type of tension spring was made of a retangular
plate with a half-circle bend in the center and the long sides bent
flat with a 1/8" radius half-circle cut-out in the center of the long
sides (end view like an omega, looking at the short sides; top view, a
sort of fat H, wider than it is tall). Drill and tap the cover plate
in the center, run a screw into the tapped hole, and you have a
tweakable xtal. Tweak too far and it may break; that's at your risk
and no liability on the part of the writer is implied or assumed.
Offer void where prohibited. :)
What's the best trick to keep from overshooting your desired frequency?
Go slow, check often. Most GDOs will work for xtal checking--tune
it in on your receiver to check freq. If you run up the meter
sensitivity, a good crystal will give a lot of deflection. A
five-prong or octal tube socket and some plugs that'll fit the coil
jacks on the GDO make a nice test fixture. (A five-prong socket can be
wired to fit both "doorknob" and FT-243 rocks, a trick I saw for the
first time last week and am now finding in a lot of places--tie pins 3
& 4 together, and use pin two for the other connection). If you
like fiddlin' measurements, buy a cheap micrometer; measure the
thickness, check freq; grind a bit and check & measure again. By the
third iteration, you'll be able to plot a fair curve correlating
thickness and freq, which will hold pretty close for other crystals of
the same type and range. Still need to fire it up and see in the
last stages, especially if you're trying to hit a specific freq.
(There are ways to fake up a micrometer, with a well-calibrated dial
and fine-theaded hardware, a Depression-era trick; using a real mike
is probably just as cheap nowadays).
Hope that's of some use. 73, --Bobbi
From: "Ray L. Mote" Subject: Re: Xtal Grinding
Bon Ami powdered cleanser makes a good grinding paste. Been using that for over 30 years now.
The plate glass out of the front of an old (BA-era) TV set makes a good grinding surface. Just spread the paste on the glass and have
very gently with a circular motion.
N E V E R try to grind both sides of a crystal using this technique! Put a bit of permanent ink or whatever on one side before
starting, to show you which side not to grind on each attempt.
(Translation: always grind the same side.)
Never tried grinding the edges. Will have to let those with experience talk about it.
I've never had decent results more than 5-7 Kc away, if I remember correctly. (Yeah, I've got Crumbling Mind Syndrome like a lot of
There were a number of articles written on this topic in QST, CQ, 73, etc. If you can get next to a CD-ROM version of "From Beverages
Through Oscar", you might do a search on XTAL and grinding.
From: "nuusers" Date: Sat, 5 Aug
1995 21:56:37 EST Subject: Re: Help in FT-243 Grinding
Back in 1969 I was interested in making a xtal filter for 455 Kc
(oh,oh, I mean 455 Khz) and an old timer showed me how to "edge grind"
old military xtals. The ones I used had a lead fused to the each side
of the thin material. It worked great...in fact an other old timer
gave me about 100 of the xtals...I think they worked in the SCR-522
sets but there fundamental freq. was 400-500 Kc range...to build him a
On the presure type (FT453 I think) xtals, the secret is to take your
time...use 100, 200, 300, and 400 grit NON EMBEDDING grinding compound
(Clover brand). The only place I have ever seen it for sale is
machine tool and gun smith supplies. Do not use valve grinding
compound as it is an imbedding type!! You take it down fast with 100
then go to 200 and finish polish with 300 and 400. You use a flat
plate glass piece to grind on. Once you are finished you let the xtal
soak in for about a week in old developing solution that has been used
a lot...this silver plates it. Take the xtal out of solution with
cotton gloves so as not toget grease or rub off the coating. Take a
clean piece of plate glass and put white tooth paste on the glass and
rub the coating off the edges. There is also a trick for measuring
activity and frequency with a sig gen, vtvm and a freq meter...but I
can't remember off hand...good luck!!!
From: email@example.com (John Wendler) Subject: Crystal
In re: Crystal Grinding... Bobbi's summary looked pretty good, from
what I remember reading. I remember also seeing something about using
Hydroflouric Acid as an etchant, but would discourage anyone from
pursuing this option unless they are a trained chemist operating in a
proper lab with proper garb. HF is absorbed through the skin and goes
to the bone. All reports indicate that this is extremely painful.
I looked into crystals at one point from a professional perspective;
checked into the books and talked with some colleagues who make the
world's lowest phase noise SAW devices. Suffice to say that
cleanliness, proper processing, and good materials are all necessary
to go for "world class." For well made crystals, the differences in
performance between nitrogen atmosphere, ambient atmosphere, vacuum,
in a cold weld or resistance weld or a glass package are all very
noticeable. The presence of a gas will dampen the vibrations,
decreasing the Q. Contaminents will settle on a crystal, lowering the
frequency and the Q; this can be part of the aging characteristics or
a deliberate tuning strategy. Pencil lead, anyone? How about water
vapor from the atmosphere, and dust in the package?
You can guess where WWII crystals end up in the general scheme of
things, as well as crystals for microprocessors, etc that are cranked
out by the million. We are fortunate that we do not require world
class for amateur application!
One book had a calculation of the acceleration that an atom on the
surface of the crystal suffers... I seem to remember ~1,000,000 G.
Deflections were on the order of an atomic diameter, if the memory
hasn't completed faded this morning. I would certainly expect the
lead to move around over the long term, thus changing the frequency
I hope this background gives a little insight into why tuning with a
pencil can sometimes cause problems, both long and short term, as well
as why some of the old style crystals might require periodic cleaning
as Bobbi mentioned.
A common cleaning process in many semiconductor fabs (for grease
removal) is (was? EPA?) some kind of Trichloro for grease removal,
followed by methanol for Trico removal, followed by de-ionized water
for methanol residue removal. The DI water is then baked off. I used
something similar to this while preparing samples (electronic, not
insectile) for a scanning electron microscope. (There! I got mention
of a hollow state device into this post, so it's partially
You may want to consider distilled water from the supermarket for the
final clean up of your crystal. I know that I would not use the water
from my faucet to clean it; it's loaded with iron!
BTW, you may want to check your can of Tuner Cleaner/Degreaser
ingredients; my can will double for the Trichloro and alcohol steps
above, even though the ingredients are not exact.
73 es GL John
From: "Roberta J. Barmore" Subject: Re: Xtal
Hi! I'd like to expand on the following, for the benefit of the
younger folks. (It's just a good thing my rheumatiz' isn't actin' up,
On Sat, 5 Aug 1995, Ray L. Mote wrote:
- N E V E R try to grind both sides of a crystal using this
Occurs to me it's might not be clear why this is so--you see, if
we want our xtal to be a good one, both sides need to be parallel
(if not, you can end up with a dead'un--or worse) and remain at the
original angle to the crystalline structure of the quartz. In
particular, the AT-cut is a bit fussy; you can think of this common
cut as a way to combine the frequency vs. temperature characteristics
of the ol' X and Y-cut rocks, which are opposite in sign but of
differing slopes. [Real Engineering and Science types among us will
know I'm glossing over a lot in that assertion, but it covers the
gross effects]. Get too far off, you've got a drifty rock, and the
poor feller with a super-solid-state-Whizbang Wonder xcvr will not
be able to follow you; he doesn't know from drift. A hardware-store
micrometer might be very useful for checking parallelism, especially
if you plan to do a lot of crystals. (At what they're getting for 'em
new, moving the surplus ones is pretty attractive!) There's also
some things having to do with surface smoothness that come into play,
and saving at least one of the original surfaces helps keep the rock
active--might be wise to put the side you've been grinding against the
plate that's got a spring right back of it; last time I opened up a
junk FT-243-type holder, there was only a spring on one side. (Dunno
if they're all that way).
Oh, the flattish metal spring I mentioned in an earlier post can be
found in some types of mil-surplus crystal holders. (I found the
article). Interested parties can e-mail me for details & such. Think
it was the March '62 CQ.
A source tells me Petersen is looking to get back into crystals for
ham gear. Anyone know for sure? Can't seem to find their number....
From: firstname.lastname@example.org (Sheldon Wheaton) Subject: Re: Help in
I've ground quite a few xtals for my use in the Antique Wireless
Association's annual CW QSO contests (Rig is 1939 vintage reproduction
6L6-809). A couple of my comments on the subject:
For a given type of "cut" (direction of XTAL lattice molecular
alignment), the fundamental frequency is inversely proportional to the
thickness. Most FT-243 xtals are "AT" cut. The formula is listed in
many early (1930's) ARRL handbooks. Using this formula, and a good
micrometer, you can make some rough cuts without having to assemble
the crystal every time.
Keep your eye out for old xtal grinding kits at hamfests. I have some
with different "grits" of grinding powder. Not sure what it is, but
looks & feels about like talcum powder, except gray in color.
If the xtal is not ground with both sides parrallel, you may end up
with two or more different "fundamental" frequencies! Not good.
Sometimes an otherwise good xtal that worked fine, but won't oscillate
or does so erratically after the last grind that moved it only 5 kc or
so, can be made to work correctly by slightly "beveling" all four
edges on both sides (8 edges total). This procedure is documented in
many books of the 30's. It usually doesn't need to be a visible bevel,
just a few "strokes" with the compound.
I have best luck with a figure 8 motion for grinding. Some grinding
kits have a flat piece with a pentagon shaped, shallow cut-out, with
inwardly curved edges, which will make the quartz piece move around in
an impressive "Spiro-graph" type motion, but I haven't had much luck
with this item.
gud luck & 73, Sheldon KC0CW email@example.com
From: firstname.lastname@example.org (Roy Morgan) Subject: Re: Help in
Greetings fellow boatanchorites!
I need help from all the BA gurus out there practiced in the mysterious art
of grinding FT-243 type surplus crystals to operate in the ham bands.
Here are some short notes on your questions:
-use wet finest possible wet-dry emery paper, or fine carborundum or even toothpaste on a piece of glass.
-activity goes up and down as you grind the frequency upwards. You may have just gotten to a poor spot on most of your crystals because
of the distance you moved the frequency.
-activity at/near a frequency depends on thickness/width ratio so activity can sometimes be restored by grinding the edge(s) of the
crystal. Frequency will likely got up as you grind the edge. Do a
LITTLE at at time.
-a crystal in a holder with some dust will act strange, if it oscillates at all, so be CLEAN when assembling. Handy things to have
are: acetone or alchohol, clean - the kind you might get at the paint
store may not be too clean (and ventilation!), little soft brush from
the art store, blower like a bulb-type solder sucker or baby nose
-increasing spring pressure in the holder will usually increase frequency, I think. beware of cracking the thing.
-a bit of pencil lead or solder rubbed on the flat surface will lower the frequency by making it heavier, and doing this may help you
predict what will happen if you grind the edges.
-capacitance of the oscillator circuit may affect the activity of a crytal you've ground.
I'm intersted in making up a "standard" oscillator circuit - I have a
handbook giving lots of tube circuits. I'd be glad to cooperate on
this project if you'd like.
-- Roy -- Roy Morgan / Tech A-266 / NIST / Gaithersburg MD 20899 (National Institute of Standards and Technology, formerly NBS)
301-975-3254 Fax: 301-948-6213 Internet: email@example.com
From: Andy Wallace Subject: xtal grinding monitor --
someone TRY THIS.
Also in the '49 Hints and Kinks book is a method (page 88) of
monitoring the frequency of a quartz crystal DURING GRINDING.
Take a flat piece of aluminum or copper about 6" square, and connect
it to your receiver antenna post using a short lead. Place the plate
glass on which the grinding is being done on this sheet. You can tune
in the crystal frequency on the receiver by the scratches you hear as
the crystal is being ground.
This is the first time I've ever heard of something like this, but I
assume the laws of physics and piezoelectricity allow this to work.
'scuse me, I have to go take apart a picture frame and find some PC
board material! But seriously, would someone on the List volunteer to
try this? Fascinating...
P.S. The H+K book also recommends automotive valve grinding compound
for speedy xtal grinding. Hmm...I smell some new Novice xtals coming
on, maybe even for 80m.