[Hammarlund] crYstals for SP600

Mon, 14 Oct 2002 16:50:13 -0400

You can order them from http://www.jancrystals.com
but you have to calculate the frequency first. It is not just the dial
frequency.

If all you want to do is test the FCU, then any crystal in an HC-6 package
will do. The R-390 receivers are full of them, so you can just yank one. In
general, you would need an oscilloscope or an RF voltmeter to tell if it was
working, unless it was for WWV or something easily recognizable. Unless it
is a crystal for a frequency where something you know is broadcasting, you
can't tell whether it is working or not.

Here is the formula for the crystal frequency:

(1) Lower 3 bands, up to 7.4 MHz, add 455,000 Hz to the desired frequency.
(2) 7.4 MHz to 12.0450, add 3,955,000 Hz to the desired frequency
(3) 12.0450 to 44.0450, add 3,955,000 Hz and divide by 3
(crystal operates in 3rd harmonic mode in this band)
(4) 44.0450 to 54, add 3,955,000 Hz and divide by 4
(crystal operates in 4th harmonic mode in this band)

If someone just hands you a crystal, you can figure out what frequency it
will receive on by reversing the above table. You will notice that crystals
just above 7.5 MHz can be used on either the 3.5-7.5 band or the 7.5-14 MHz
bands and they will receive on different frequencies.

They will want to know several things: series or parallel mode (and what
parallel capacitance), and what impedance you want. You can tell them the
following:

(a) You want it in the HC-6/U can
(b) You want PARALLEL mode with 35 pf parallel capacitance.
(this is roughly the mid-point of C65, the FCU trimmer)
(c) You want the lowest impedance you can get. Maybe 200 ohms if they can
make it. Ask for 200 ohms. They will either complain or not.
(d) For the 3rd and 4th harmonic crystals, tell them that. They will test it
at that specific harmonic.

JAN charges about $15 each and it takes them about 6 weeks to grind it and
send it to you. They will sell them in ones and twos. I have used them
several times in the past with great results.

Enjoy!

James A. (Andy) Moorer
www.jamminpower.com

----- Original Message -----
From: "Raymond Brown" <[email protected]>
To: <[email protected]>
Sent: Sunday, October 13, 2002 5:10 PM
Subject: [Hammarlund] crYstals for SP600

> I have a early SP600. I would like some crystals just to see if that part
of
> the radio works? Is there anyone who makes them or has them?
> Thanks Ray Brown
>