[time-nuts] Frequency standard

[jimlux]

On 1/26/19 5:00 AM, John Ackermann.  N8UR wrote:
> Hi Bob --
> 
> A GPSDO can replace the OCXO in your counter, and that's now most folks would use it.
> 
> If you just want to calibrate the OCXO, you don't need a GPSDO -- you can do that with just a GPS that has a pulse-per-second output, and a scope.
> 
> Use the GPS PPS to trigger the scope and adjust the OCXO for a stationary display of the OCXO waveform.  It's easiest if you use a PPS derived from the OCXO (there are inexpensive dividers that will do that) but you can also do it by looking at the 10 MHz directly -- adjust until the zero-crossing point of the sine wave stays put; when you're more than 1 Hz off you'll need a bit of guesswork, but once you get within 1 Hz you'll be looking at the same cycle position each second.  If it takes 10 seconds to drift one cycle on the display, you're 0.1 Hz off.
> 


or even simpler, use the counter to count the time between 1pps ticks. 
Direct reading of the OCXO frequency.






> John
> 
> On Jan 26, 2019, 7:15 AM, at 7:15 AM, "Richard (Rick) Karlquist" <richard at karlquist.com> wrote:
>>
>>
>> On 1/25/2019 10:06 PM, Bob Albert via time-nuts wrote:
>> accuracy of only about 1 part in 20 million.  I want it somewhat
>> better,
>> but no way do I need it 100 times better.  If I could set it within 0.1
>>
>> Hz that would be fine - it would enable frequency
>>
>> You're kidding yourself on the 1 part in 20 million.
>> The propagation effects are such that there is
>> doppler shift on the frequency that you hear that
>> is much greater than that number.  You really do
>> need GPS.
>>
>> Rick N6RK
>>
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