[time-nuts] GPS Crystal Frequencies

Baker Douglas kfourcle at gmail.com
Tue Oct 27 08:18:07 EDT 2015

Hello Brooke,

It has been a while since we emailed each other - hope you are doing well.

The 10.949297 MHz oscillator in GPS receivers was (I think) chosen by
Rockwell in the early days when they wanted a frequency that work for both
L1 and L2 receivers.  If you multiply the 10.949 times 128 you get 1401.51
MHz. for the local oscillator in the receiver.  That will give you a first
IF of 173.91 MHz.  If you add 1401.51 MHz and 173.91 MHz you get 1575.42
for the L1 channel.  If you subtract 173.91 MHz from 1401.51 MHz you get
1227.6 MHz for the L2 channel.

So the receivers you have were most likely designed to work as either L1 or
L2 or maybe both.  Using the 10.949 MHz oscillator frequency made it easy
for the receiver manufacturers to produce receivers for the military that
would be for L1 and L2 channels.

Hope this helps.
Best regards,
Doug, K4CLE

On Mon, Oct 26, 2015 at 9:06 PM, Brooke Clarke <brooke at pacific.net> wrote:

> Hi:
> I understand 10.230 MHz since when multiplied it gives 1176.45,1227.60,
> 1381.05 & 1575.42 MHz, all GPS carrier frequencies.
> http://www.prc68.com/I/DAGR.shtml#GPSs
> But I've got a number of GPS receivers that have Rakon unit oscillators
> with a frequency of 10.949297.
> http://www.prc68.com/I/DAGR.shtml#Polaris_Link
> What's the story?
> PS I'm looking for documentation on the Polaris Link (civilian) GPS board.
> Mail_Attachment --
> Have Fun,
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> http://www.prc68.com/I/DietNutrition.html
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