[R-390] Crystal 200 KC

Sun Feb 24 22:10:05 EST 2008

Hi

I"m not sure that we all understand just how unusual a crystal the 200  
KC rock really is.

Most of the crystals in the R-390 are AT cuts. They are as common  
today as they were back when the radio was new. Quartz is grown  
oriented to make cutting AT blanks efficient and cheap. You can buy  
cut to spec blanks from companies in at least a dozen countries.  
That's true weather you want to buy one or a million pieces. There are  
hundreds of companies worldwide that can and do make AT's that are  
capable of being dropped into an R-390.

Below 1 MHz AT's become impractical. A number of other cuts are used.  
The raw quartz needs to be oriented correctly for each cut. The blanks  
get big and the cutting becomes difficult. To really appreciate what  
all that means you have to get into some nasty physics. Forty years  
ago there where maybe ten to twenty people in the world who actually  
did it. That's not companies, I indeed mean people who could set the  
cutting up.

Next up is that people have simply stopped making crystals below 1 MHz  
the way they used to do it. The approach now is to use a tuning fork  
or flex bar that uses enormously less quartz than the old cuts did.  
Your 32 Khz watch crystal is one example. It would not sell for 3  
cents if they hadn't done an enormous change in it's design. You could  
make 500 watch crystals out of the quartz in one old style crystal.

By making the crystals smaller they changed their characteristics. The  
electrical performance of the tiny crystals is very different than the  
big old ones. They don't work in the same circuits.

Finally this is an oven crystal. It's temperature characteristic is  
*very* different than a room temperature crystal. That makes it a rare  
bird in a rare flock of birds.

Most of the low frequency work in this country ten to twenty years ago  
was going into 455 KC crystal filters. What ever is left of that  
effort is bits and pieces. Adapting a filter crystal setup to chop  
200KC frequency standard crystals is going to be a real chore.

When I asked the guy at Collins *why* he designed this crystal into  
the R-390A, his answer was simple - "we were sold a bill of goods".  
Oddly enough through the course of many mergers I now work for the  
company who sold him that bill of goods ... small world. ...

We haven't made those crystals in 20 years.

Hang on to any of these you have. If you part out a radio, keep the  
200 KC crystal. Unless you want to cobble something together, they  
will be the death of more radios than dead power transformers.

Bob

On Feb 24, 2008, at 6:12 PM, <wb5uom at hughes.net> <wb5uom at hughes.net>  
wrote:

> I got in on the tail en of this I guess. You might try (for grins):
> http://www.icmfg.com/crystals.html#ranges
>
> Now I know they are not really interested in selling just one or two  
> BUT
> I called a place one time looking for ONE special intergrated chip,  
> not a
> 1000 or 10,000 just ONE. I called them and the lady said they didnt  
> sell in
> that small of quanity BUT if I was doing a pilot project they would  
> send me
> 1- 20 for FREE !!
> It took me just a microsecond to affirm this was a "pilot" project !!!
> Have plenty of spares now!
>
> So, it might not hurt to make a call!
>
> David/WB5UOM
>
>
> ----- Original Message -----
> From: "Bob Camp" <ham at cq.nu>
> To: <roy.morgan at nist.gov>
> Cc: <r-390 at mailman.qth.net>
> Sent: Sunday, February 24, 2008 4:39 PM
> Subject: Re: [R-390] Crystal 200 KC
>
>
>> Hi
>>
>> The problem with the 200 Kc crystals is that they are not a "normal"
>> low frequency cut. You have to chop quartz at a special angle for  
>> oven
>> crystals at that frequency.
>>
>> It's not going to be easy to find somebody doing that.
>>
>> Bob
>>
>>
>> On Feb 23, 2008, at 10:31 PM, roy.morgan at nist.gov wrote:
>>
>>> Quoting Patrick <brookbank at triad.rr.com>:
>>>
>>>> Wow, the last post went OK ok, could someone let me now a source
>>>> for a 200
>>>> kc crystal and aprox. the cost??? Thank....Pat
>>>
>>> Patrick,
>>>
>>> There have been found one or two souces of low frequency crystals.
>>> Most
>>> manufacturers will not make them any more.
>>>
>>> There have been reports of one fellow in Mexico I think, but I don't
>>> have any
>>> info on that source.
>>>
>>> The only other one reputed to make low frequency crystals is:
>>>
>>>
>>> Universal Crystals Inc.
>>> Jim Little
>>> Private Company, Headquarters Location
>>> 5407 Payne St., Shawnee Mission KS 66226,
>>> United States
>>> (913) 334-6254,
>>> Line of Business: Manufacturing: Quartz crystals
>>>
>>> Here is the source of my information:
>>>
>>> To: <PHIL13 at STNY.RR.COM>; "Collins Reflector Posting"
> <collins at listserve.com
>>>>
>>> Sent: Friday, July 01, 2005 12:46 PM
>>> Subject: Re: {Collins} xtal-75a-1
>>>
>>> At 03:52 PM 6/30/2005, you wrote:
>>> Is there a source for the 500 kc xtal for the 75a-1? or does someone
>>> have one to
>>> sell?
>>>
>>> Phil and others,
>>> I have just gotten the following from Glenn Nash about a source for
>>> low
>>> frequency crystals:
>>>
>>> "Mel" is the guy at:
>>> www.mhelectronics.com.  (800 643 9825)
>>>
>>> Mel said that the best guy on the planet for those is : Universal
>>> Xtal in
>>> Kansas City, phone 913-334-6254 ask for Jim Little.
>>>
>>> I called Little and lo and behold he says he bought up just about
>>> every low
>>> frequency xtal blank in the US and is at this very minute cranking
>>> out a bunch
>>> of 455KC types. They are a bit expensive, around $50, but less than
>>> half what
>>> International Xtal gets for their low freqs.
>>>
>>> Try to contact  "Mel" and let us know what you find out, please.
>>>
>>> Roy
>>>
>>>
>>> Roy Morgan
>>> 13033 Downey Mill Road
>>> Lovettsville VA 20180
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>>
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>
>