[time-nuts] Re: Loop Antennas

[Poul-Henning Kamp]

> You will need a broad-band (non-resonant) loop for receiving Loran-C, due
> to the much wider modulation bandwidth of the signal.

Need and need...

For stationary timekeeping purposes, with minute-or-longer
integration time, less than three kHz bandwidth can work OK.

Lower than three kHz, figuring out what is the correct
zero-crossing gets too ambiguous.

But you get really big gains in both S/N and time stability
with a "HiFi" antenna which is flat from 90 to 110 kHz.

Note, that it should be "flat" in both amplitude and phase,
Loran-C, being spread-spectrum, gets really funky if you have
significant delay-distortion (aka. group-delay) across your
pass-band - however wide you decide it should be.

One advantage of going broadband, for instance 20-200kHz, is that
you can receive a lot of other signals at the same time, with the
same SDR implementation, for instance 40, 60 and 66â
”kHz timesignals.

-- 
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