[time-nuts] GPS Crystal Frequencies
brooke at pacific.net
Tue Oct 27 17:13:43 EDT 2015
Thanks very much. I've added a diagram to my GPS frequencies paragraph:
scroll down a little.
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:
I think the Northern Telecom GPS Satellite Simulator STR2760 synthesizes the needed 10.23.
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.
The prior art GPS receivers used heterodyne receivers which were much more expensive.
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:
>> I understand 10.230 MHz since when multiplied it gives 1176.45,1227.60,
>> 1381.05 & 1575.42 MHz, all GPS carrier frequencies.
>> But I've got a number of GPS receivers that have Rakon unit oscillators
>> with a frequency of 10.949297.
>> What's the story?
>> PS I'm looking for documentation on the Polaris Link (civilian) GPS board.
>> Mail_Attachment --
>> Have Fun,
>> Brooke Clarke
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