[Hammarlund] SP-600-JX-6

[Roy Morgan]

>    On Monday, April 24, 2017 7:42 PM, "wb3fau55 at neo.rr.com" <wb3fau55 at neo.rr.com> wrote:
> Folks, I got another question about the fixed freq operation.  As I can only guess,  how does one determine the freq of a crystal?

On Apr 24, 2017, at 7:59 PM, Joe Connor via Hammarlund <hammarlund at mailman.qth.net> wrote:
> Russ, Andy Moorer has an explanation on his website.

Which website is:

http://www.jamminpower.com/main/sp600.html
In summary here is the explanation: (International Crystal is now out of business!):

ABOUT THE CRYSTALS 

I have had a number of questions about the crystals in the FCU (Frequency Control Unit) of the JX models. Getting a crystal is not a difficult process. International Crystals will be happy to sell you as many as you want, even in the antique HC-11 package, at about $15 each, custom-cut to your frequency. You do have to get the frequency right. It is not just the frequency of the station you are trying to receive. Here is a reduced version of the chart to figure out the crystal frequency, given the frequency of the desired station: 

To 7.4 MHz - add 0.455 MHz to get crystal frequency
7.4 MHz to 12.05 MHz - add 3.955 MHz
12.05 MHz to 44.05 MHz - Add 3.955 MHz and divide by 3 (3rd harmonic)
44.05 MHz to 54 MHz - Add 3.955 MHz and divide by 4 (4th harmonic)

Further, this info is in “The Manual” so you can read all about it there.  There are MANY versions of the manual on Andy’s page, so take your pick!

Roy

Roy Morgan
k1lky68 at gmail.com
K1LKY Since 1958