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Re: LF: EbNaut on MF

To: [email protected]
Subject: Re: LF: EbNaut on MF
From: Paul Nicholson <[email protected]>
Date: Mon, 15 Feb 2016 12:42:21 +0000
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Markus wrote:

> note that tonight all my recordings are a little late,
> lacking the first 30 seconds of each sequence.

No problem, that would only make a small difference to the
error rate.  Plenty of spare dBs on the decodes so not
really much of a test of EbNaut but I'm happy to see EbSynth
holding steady with the 9th harmonic.

Ran some NEC models and it looks like the ERP is below 50mW,
due to the very low height of the long wire.  Does that sound
reasonable for the signal strengths you're getting Markus?

The tx ran all night and is still on.

This evening I'll do some alterations to improve efficiency
(which I can do best on a dummy load).

A very bare-bones class C push-pull with Pi network low pass
filter.  The output is a nice sine wave but with a bit
of power supply 100Hz ripple.  The coils are wound with some
scrap wire (to get the number of turns right) and they
run a little warm.  I want to see what difference it makes
replacing them with some thicker wire or copper strip.

Then will dismantle the tx unless anyone else wants to try a

G4WGT was kind enough to leave his online grabber running
(normally it is only on at the weekends).  Gary is only 35km
distant so it is very handy for testing.   On Sunday I was
measuring the antenna feed impedance using a small signal
generator and noticed a faint line on Gary's display!  The
ERP must have been in the microwatts.  Also, I see a little
QSB even at that short range.

Might have a play with LF next, before the multiplier and
PA parts go back into the junk box.  I'll have to wind a
bit of loading coil for that one, or run out some more wire.

I could only find 3 grabbers for the MF band but there are
lots covering LF.    Is MF not so popular?

Paul Nicholson

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