[time-nuts] LORAN C antenna thoughts from the group

Poul-Henning Kamp phk at phk.freebsd.dk
Tue Dec 21 19:58:17 UTC 2010


In message <53187.12.6.201.2.1292957970.squirrel at popaccts.quikus.com>, "J. Fors
ter" writes:

>I remember reading somewhere that the envelope of the LORAN pulses was
>shaped to reduce the transmitted BW.

The envelope is designed for two things:  sensible BW and ease of
production.  There is some math musing about it in the Radiation Lab
book.

>Does anybody have a reference for that, and relatedly, what does the BW of
>the antenna have to be? Typically, loops are about 90 KHz to 110 KHz, but
>can that be narrowed down?

In principle you can make it as narrow as you want, and compensate
for the resulting pulse-shape distortion in your receiver.

Going much wider than 30kHz (85-115kHz) usually results in more
interference from CW signals than improvement to the loran signal.

You can see a typical power spectrum at the bottom of this page:

	http://phk.freebsd.dk/loran-c/Antenna/

Poul-Henning

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Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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