[time-nuts] LORAN C antenna thoughts from the group
J. Forster
jfor at quik.com
Tue Dec 21 20:11:40 UTC 2010
I was more interested in reducing the BW, rather than increasing it.
Years ago, I bought up some of the resuidual of Appelco, a New Hampshire
LORAN company that made units for Raytheon. Included were a bunch of
active tunable filters, designed to "tune out" interference. However,
there is no documentation.
I was just toying with the idea that a good shielded (possibly active)
loop, the tunable filters, and an Austron 2100F might still be usable on
the east coast.
FWIW,
-John
================
> 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
>
> --
> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG | TCP/IP since RFC 956
> FreeBSD committer | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by
> incompetence.
>
>
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