[time-nuts] GPS Crystal Frequencies

Brooke Clarke brooke at pacific.net
Tue Oct 27 17:13:43 EDT 2015


Hi Doug:

Thanks very much.  I've added a diagram to my GPS frequencies paragraph:
http://www.prc68.com/I/DAGR.shtml#GPSs
scroll down a little.

Hi Paul:

The 10.23 is a key number for a transmitter.  For example the Stanford Telecom 5001 test transmitter which uses a high 
quality 10.23 xtal oscillator:
http://www.prc68.com/I/5001A.html
I think the Northern Telecom GPS Satellite Simulator STR2760 synthesizes the needed 10.23.
http://www.prc68.com/I/NTgpsSTR2760.shtml

The first generation Trimble Trimpack (PSN-10) GPS receivers were all built on their key patent.  It's a direct 
conversion receiver using a hard limiter with I&Q signals.
http://www.prc68.com/I/Trimpack.shtml#Pat
The prior art GPS receivers used heterodyne receivers which were much more expensive.

Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Baker Douglas wrote:
> 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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