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Re: LF: NA VLF

To: [email protected]
Subject: Re: LF: NA VLF
From: Paul Nicholson <[email protected]>
Date: Sat, 13 May 2017 20:33:14 +0000
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Joe wrote:

> The aerial has nul towards the west on 2200 and 630 metres

I don't expect you'll get any directionality at all at VLF
It will closely approximate a vertical Hertzian dipole, whatever
you use.

> Last night the wire acquired a layer of ice and the current
> dropped by a factor of 5.

Re-tuning is a problem, because it will leave the signal at
a new phase. I will lose the signal for a few hours each
time you adjust the tuning.   Some sort of phase feedback is
desirable so that if the tuning has to be tweaked, the feedback
will shift the TX phase to maintain the original radiated phase.

> the raspi/tx are QRV for ebnaut.

We would have about a 30% or 50% chance of success at the moment,
so might take 2 or 3 attempts to get a 3 or 4 char message
across.  Recent nights have been quite noisy.

There's about a 6 hour nighttime window, but it varies a
bit.  Sometimes good 22:00 to 04:00, sometimes 00:00 to 06:00
is better.

You could try 8K25A 3 chars, 55 second symbols with CRC=8
to begin around 23:00 UT.   That would be an easy decode
with the S/N we got overnight 7th/8th.

A bolder test would be 8K25A 4 chars 50 seconds CRC=8.

Something on the limit, needing a quiet 8 hour window
would be 8K25A 5 chars 58 seconds CRC=8 to run from around
22:00 UT.

A conservative attempt would be 8K25A 2 chars 70 seconds CRC=2
from 23:00 UT.

--
Paul Nicholson
--

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