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

Peter Monta pmonta at gmail.com
Thu Mar 30 23:00:31 EDT 2017

> 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)
True.  I've been wanting to try this with an FPGA transceiver; even the
cheap ones go to 6 Gb/s now, but binary only.  The newest transceivers
support PAM-4, which would be great, but they're not affordable yet.  Also
that's a lot of gain at one frequency.


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