[hpsdr] GPS 1pps output

[K4KV]

Glenn,

Yes this would be a software solution, except that at 2M, you would need 
a pretty robust micro to

accept that high a frequency in its counter input.  Probably a prescaler 
chip would be required.

I know some of the PIC chips could take up to 60Mhz input.

73

Glen K4KV



On 6/13/2018 02:13, Glenn Thomas wrote:
> Hi Glen (1 n!)
>
> One approach is to use the 1 pps to gate a counter that's counting the 
> oscillator frequency. The oscillator can then be adjusted based on the 
> difference between the measured freq and the desired freq. The 1 pps 
> from a GPS can be accurate to <1 ns, which is better than 1 Hz in 1000 
> MHz. The internal GPS clock period is known to the GPS software to 
> within 0.1 ns - it's part of the navigation solution. Whether the 
> output 1 pps is controlled to this level of accuracy or not is a 
> design detail in your GPS box!
>
> 73 de Glenn (2 n) WB6W
>
> On 6/12/2018 5:50 PM, K4KV wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hello,
>>
>> I have just ordered a qrp labs beacon kit with a gps unit that has a 
>> 1pps output.
>>
>> I have been told that they use software to 'read' the gps and then 
>> automatically
>>
>> correct the Siliconix programmable oscillator.  Granted, this takes 
>> quite a while to
>>
>> get it right.
>>
>> But still, I cannot see how it can be very accurate compared to a 
>> 10Mhz GPS output
>>
>> reference.
>>
>> These 1pps output modules are quite inexpensive.
>>
>> Can someone point me to a white paper where someone describes how to 
>> use software
>>
>> to correct a programmable oscillator using a 1pps system?
>>
>> 73
>>
>> Glen K4KV
>>
>>
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