K5LAD - 50+ Years of Ham Radio Memories

Volume XXVIII

 

Not the Same Old Grind........

 

Search keywords:  crystal, grinding, novice, FT-243. 

Early memories of ham radio

 I just recently started thinking back to my earlier days when I tried my hand at grinding my own crystals.  In those earlier days, there were very few VFOs on transmitters and just about everyone used crystals which were in an FT-243 holder.  (As a matter of fact, Novices were not allowed to use VFOs, even if they owned one of the few commercially designed and built radios that had a VFO.  Crystal-control of the transmitter was an FCC requirement for Novices.) 

 

The FT-243 holder was typically about 3/4” wide, 1 1/4” high and just over 3/8” thick.  The two pins added about another 1/2” to the height.  You might recognize this particular crystal from seeing them at a hamfest flea market or, perhaps, in a boxful of   “stuff” bequeathed to you from an old-time ham or even worse, by an old time ham’s widow. 

These crystals were really plentiful due to a bit of an international conflict the United States was involved in during the first half of the 1940s. 

Crystals 2.JPG (17484 bytes)

  Many of these crystals were even marked like “Channel 721” because it was easier to remem-ber a smaller number than a frequency.  They also were marked with the frequency in kilocycles (re-member, this was before we started using the term “kilohertz) but it made more sense to the uprooted chef to tell him, “We’ll all be on Channel 321.”
  Crystal control made military communications much easier, particularly for the soldier who had been a civilian accountant or chef so he was obviously placed (or misplaced) in the job of soldier/radioman.

In my Novice years, in the late 50s, you would never expect to hear the other end of your CW QSO on the same frequency.   The Novice band was:  80meters = 3700-3750kc, 40meters = 7100-7150, and 15meters = 21100-21250.  Every Novice tried to have at least one crystal for each band and if you had several for each band then you were envied by other Novices.  The crystals for the 15 meter band were in the range 7034kc to 7083kc as they were multiplied by 3 in the transmitter.  Also, there were few, if any, military surplus crystals in the 21 Mc. range but many in the 7000+ range.    You would call CQ using the crystal you had available, then tune the entire Novice CW band to find someone answering you on the crystal that they had available.  QSOs were seldom on the same frequency unless the other station had bought their military surplus crystal from the same source you had used.  This is why, if you were answering a CQ and had several crystals on each band, you could plug in the one that was closest to the other station calling.  Also if a very strong station seemed to be camped out on a particular frequency, you could swap crystals and not need to wait for his arm to cramp up so he’d relinquish that frequency.  If you only had the one crystal, however, it was time to try a different band or re-read your QST magazine.

These crystals sold for about $1.00 to $2.00 each and that was money was not always available to the young Novice.   Seems like I owned 2 crystals for 80 meters, 2 for 40 meters and 3 for 15 meters.  Even after my Novice years were a decade behind me I remember receiving a shipment of surplus “goodies” which were courtesy of Army MARS.  As I opened the rather large crate, like a small child at Christmastime, and withdrew those wonderful military surplus treasures, I came upon an olive-drab colored box measuring about 10” x 7” x 2” and labeled, “Crystal Set.”  

I thought how strange it was for the military to have been using such a simple radio device as an old crystal set during the war effort, but when I opened the box, I saw heavy paper dividers, dividing the box into small rectangular spaces and each space was filled with an FT-243 crystal which was 25kc from the one before and after it.  In other words, they started at 5675kc, the next one was 5700kc., the next was 5725kc., etc.  What a joy that was and it was complete, i.e., every space was filled with the proper crystal.   At that time I was getting interested in 2 meters, both AM and FM and I needed some 8 MC range crystals to multiply up to that band……. now I had them.

 
NOTE:  There are several spots now empty in the picture of the box.  These are crystals I actually used and never replaced in the “set.”  They may still be in use in a project or may be now missing and comfortably resting in the same place where those socks go when missing from the dryer.

The really lucky Novice was one who had a job that could bring in a little money to help finance their radio hobby.   With money in hand, it was often back to the catalogs to find companies who were selling those military surplus crystals.  Quite often there was not a large selection of frequencies.   If you had sufficient funds, you dreamt of having a crystal on about every 2nd or 3rd kilocycle, all the way across the band.   If the government had seen fit to manufacture a crystal on the frequency that you wanted……….. and you could find that frequency; you were very much in luck.  If, however, you couldn’t find what you wanted, it was time to grind or “lead” an existing crystal to the desired frequency.

To modify a crystal to another frequency, you needed to start with a crystal that was lower than the target frequency since grinding moved it up in frequency.  The crystal blank inside the FT-243 holder was about  ” square and about a millimeter thick.  The thinner it was (generally) the higher frequency it would oscillate.   The actual oscillating frequency was a function of the thickness and was also dependent on a ratio of the crystal blank’s height and width.  If you ground off too much of the crystal’s surface material, the crystal might stop oscillating completely.  When this happened, you had to grind a small amount of material off the edges and this might work or it might not.  The crystal blank itself was very fragile and if a piece suddenly chipped off (no longer a rectangle but now with more than 4 sides) it was completely unsalvageable and had to be discarded.  If you made the mistake of accidentally dropping it on the floor, it almost surely would shatter into several, if not many, pieces.  I think many of we Novices who experienced a broken crystal blank while grinding, still held onto the holder with the impossible hope that “maybe some day I’ll run across some extra crystal blanks and I can re-use that holder.”  Yeah, sure…………….. no way, Jose.

 

To grind a crystal the screws (usually 3) holding the front side were removed.  These holders were either made of plastic or bakelite material.  Under the front piece was a rubber gasket with a conical spring (not straight but more triangular shaped with a small diameter loop on one end and a larger diameter loop on the other).  This small loop spring end was toward the metal plate holding the crystal blank and the large part of the spring toward the case.  Sometimes the spring was attached to the front removable piece of the holder and others could be removed (and dropped down the floor fur-nace or some other irretrievable spot). 

 

 

 

 

 

 

 

 

 

 

 

 

 

Upper left:  The top of the holder with the spring still attached to the rubber gasket on the backside of the cover.

Lower left:  The actual holder base.  The inner square of metal made contact with a crystal pin and with one of the metal pieces gripping the crystal blank.

The two metal squares on the right held the crystal blank and it oscillated inside them.  Each square had small raised areas on the corners to allow the slight crystal movement within them.

The translucent square in the center of the black backdrop is the actual crystal blank as described elsewhere in the article.  Very fragile, especially when out of the protection of the holder.

 

The dark bakelite square was an insulator and support that went between one of the metal crystal blank holders and the large loop of the spring.

This picture just allows a closer view of the pieces described

The crystal blank, which was a milky white translucent color, was held between two metal pieces, which were about the same size and shape as the blank.  When the crystal was assembled, the crystal (sandwiched inside the metal pieces) was under the pressure of the spring.  The crystal, when all put together properly, was relatively shockproof.  It was somewhat like items that are advertised as “fool-proofed” but there’s always some fool who can prove them wrong.  I say it was shockproof but that theory should not be tested.

Side bar:  At a Kenwood Service seminar I attended in California when I had my ham store, the Japanese instructor called that, “testing your seat belts.”  It was certainly not a recommended procedure.

Grinding the crystal blank needed to be done with clean hands and still the oils from your fingers would get on the blank so you had to wash it after each step of the grinding operation.  Now a days I’m sure rubber gloves would be the recommended attire………. plus some additional items, of course.  It was recommended that you find a piece of plate glass to use as the surface to grind on since that was one of the best really flat items you could find around the house.  The grinding material could be any number of things, if you needed to move it quite a few kcs up you might use a very fine grit sandpaper.  This was quicker but you had the threat of moving it too much, too quickly and stopping the oscillation altogether.  A better choice was toothpaste or even better, tooth powder.  These had a very mild abrasive but allowed the grinder to approach the target frequency more slowly.  Water was added to the abrasive material to facilitate the task and made a gooey and messy paste.  

The grinding is done by carefully removing the crystal blank from the holder and the metal plates and placing it on the piece of glass with the abrasive, whatever you happened to be using.  It was always recommended that you grind on only one side.   This requires the grinder to pay attention to how the blank was placed in the holder each time when you checked the frequency.   With the blank down on the abrasive, press one or two fingers on the top of the blank and move the blank in a figure 8 motion.  My hands were large so I only used one finger.  Very little pressure was applied during the grinding process.

 After about a minute of making figure 8s with the abrasive, the blank is picked up and completely washed off and carefully dried off.  Here the blank must be very carefully handled to keep from breaking it and also, keep noting which side is the grinding side.  When it was perfectly clean and dry, it could be re-assembled, plugged back into the transmitter, and keyed up to check the frequency on the receiver.  Back in my Novice days, my receiver was not very well calibrated so it was very difficult to know exactly the frequency to which it had been moved.  If you had some untouched crystals, they could be your standards and you could tell how closely to the standard you had ground the one you were working on.

A good crystal grinder did not get in a hurry…………… grind a little……….  clean the blank…….. reassemble the holder……….. check the frequency……… unassembled the holder………. grind some more ………… clean the blank, etc.  If you got in a hurry you might break the blank, or drive it out of oscillation.    It was also a good idea to keep notes to let you know things like, how many figure 8s did it take to move it and how far it moved, if your receiver calibration was good enough.  Great fun …….. so much to lose with a failure but so much to gain with success --- I saw both

I mentioned earlier about “leading” a crystal blank.  This was the procedure of moving a crystal blank DOWN in frequency and it could not be moved very far with this method.  It consisted of lightly rubbing the lead of a pencil over the blank on one side, just a small amount at a time.  The slight mass of the pencil lead would slow the oscillation of the blank but you could not deposit too much lead before stopping the oscillation.  At least, if you leaded a crystal blank too much and halted the oscillation, you could clean the lead off and try again with less.  I guess you might call that, “getting the lead out.”  I don’t recall ever being able to lead one down even as much as a full kc.

A crystal that had been poorly ground might still oscillate but might not start immediately.  The result was, an attempt to send words and letters in CW would mess your sending speed up since you were at the mercy of your crystal and its oscillation ability.  Sometimes it was:   press the key, wait a to second before the crystal started, let the key go, send the next piece of the letter but wait until you got oscillation and transmitted power, etc.  Just sending a letter C required 4 hesitations in sending.  Usually, when a crystal reached that point the neophyte would try to fix the blank, even though it was on the desired frequency, and often end up destroying the crystal blank in their frustration.  I can’t tell you why I know this to be true, however………………..

To the modern day ham, particularly if they are a newcomer, the VFO is an absolute necessity.  They might never be able to imagine not having the ability to move around over the complete band or move out from under some QRM but this was the norm several decades ago.  Even now, with digital frequency generation, you can go to an exact frequency, right down to a fraction of a kilohertz.  The good old days of ham radio were fun but I’m glad to be living in the era where most crystals are now used in filters or perhaps in mixing oscillators.

Newer hams these days, who never lived in the “Day of the Crystal,” just can’t imagine a time when you were transmitting on one frequency and talking to someone 30 or more KHz away.   In fact, except for the DXer who must work split at the request of the DX station, most hams would consider it some sort of FCC infraction of the rules to not carry on your QSO on, or very near, the frequency of the other station in your QSO.  On the low bands, the VFO is a wonderful tool……….. perhaps a necessary tool, huh?  No, there’s another way to do it……. but NOT a better way to do it.  Now let’s see…….. why was it that they were called, “The Good Ole Days”?

Jim – K5LAD

written July 7, 2009 - published in TARC Newsletter - August 31, 2010 


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