Message-ID: <38F4CF75.B42A1976@netscapeonline.co.uk>
Date: Wed, 12 Apr 2000 19:33:10 +0000
From: "g3kev" <g3kev@netscapeonline.co.uk>
Organization: Netscape Online member
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Nonsense from G3KEV
References: <JwAwOCAw$H94MwyS@telemetry.demon.co.uk>
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Tom Boucher wrote:

> In message <38F422C1.A543FFD1@netscapeonline.co.uk>, g3kev
> <g3kev@netscapeonline.co.uk> writes
> >Square wave generators/dividers and class D/E amplifiers are fine for
> >small antennas and low erp but NOT SUITABLE for larger antennas and high
> >power. An abundance of LPF and BP filters might help to clean up the
> >signal.

If you read the literature published by one of the researchers/experimenters
of class D/E amplifiers, he states that if you push the amplifiers, which
most amateurs do, and do not pay attention to the LPF, you are then radiating
a distorted square wave, with all its odd order harmonics, he goes on to say
that for larger than normal antenna systems one would need possible more than
the normal 5 pole filter between the mosfets and the antenna.
I own a quality spectrum analyser and can verify what he says to be correct.
Very few signals generated by such amplifiers and used by radio amateurs have
a pure sine wave output after one 5 pole LPF, except at very low power
levels, also have a look at the ripple content super imposed on the signal
because the power supplies normally used by radio amateurs are not regulated
or well smoothed. .
With your modest amplifier and long wire a few feet above ground you have
nothing to worry about.
G3KEV


>
>
> Absolute rubbish!
>
> 73, Tom G3OLB
> >