[time-nuts] GPS first LO need to be locked?

Magnus Danielson magnus at rubidium.dyndns.org
Fri Mar 31 15:19:00 EDT 2017

Hi Jim,

On 03/31/2017 01:07 AM, jimlux wrote:
> BTW a lot of GPS receivers don't have a "first LO".. they are more like
> a Tuned RF receiver - an input BPF for L1, L2, or L5, then direct
> sampling at around 30-40 MHz -  something that makes the GPS signals
> alias down somewhere convenient (and always have positive frequency
> offset from zero, even at max negative Doppler)

Still fills the function of LO, as the sample and hold operates as a 
mixer and the fold-down can be seen as an overtone mix followed by a 
sampling of the mix product, so well, it's about the same thing.


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