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LF: Re: 'JNT Dual purpose beacons

To: <[email protected]>
Subject: LF: Re: 'JNT Dual purpose beacons
From: "James Moritz" <[email protected]>
Date: Sat, 19 Sep 2009 13:05:59 +0100
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Dear Andy,

I would suggest a frequency between 503.825 and 503.900, to avoid the QRM around 504kHz some people experience, and give a bit of tolerance for receiver frequency errors, which are sometimes suprisingly large. For some reason, the frequencies below 503.9 seem to be less widely used. But since there are only about half a dozen stations transmitting in this mode, there is plenty of space.
A 25% or 33% duty cycle seems to be frequent enough to catch most
"openings" - probably less would be OK. As for power, I would suggest
running as much as possible - monitoring signal level of a strong beacon is
easier than a weak one, and a relatively high power will give the greatest
chance of being received by the maximum number of stations under the maximum
range of conditions. You could argue that the presence of a "strong" beacon
would sometimes prevent reception of very weak signals nearby in frequency,
but since this only can happen 25% or 33% of the time, and the signal is not
so strong at a few 100 mW ERP, it is probably not a serious objection in
practice.
Cheers, Jim Moritz
73 de M0BMU

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