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Date: Fri, 10 Aug 2012 07:33:02 +1000
Message-ID: <CAKvcm2cp1WDFZgufoDRr0D7yxBijentyvvDDkrhQzQ5vwFUeeg@mail.gmail.com>
From: Dimitrios Tsifakis <dtsifakis@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Caps for Class-E amp
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> What i forgot to say: Actually i can not recommend a class E for /p
> purposes. A class E is a fine thing and it is fascinating to see that one
> can generate 1 kW with a single FET and > 95% efficiency and without any
> ferrite transformers. But the efficiency and voltages and currents are
> highly dependant on the load resistance and eventual reactive components. As
> long as the SWR is < 1:1.5 or so, it is fine but then it becomes critical.
> I lost a FET in the field while using a 100m kite vertical antenna. The kite
> dropped and i wasn't watching for a minute and then BAANG! If you use the
> class E at home, in a fixed antenna installation with known and stable SWR,
> then this is fine.

Well, that's why I thought the monster IXYS FET I used, which is
obviously an overkill, will probably be hard to kill. I can't possibly
exceed the 55 A current limit (it's fused to much less than that) and
I won't exceed the drain (or gate) limits as it's already quite high
(500  V) but also I will add a beefy transzord or zener to ensure
compliance. The capacitors are maybe more likely to get damaged, so
that's something I need to consider by overengineering that part.

In any case, I won't experiment with kites, just good ol' plain earth
antennas which are quite robust mechanically and won't fall on the
ground because they are already there :-)


73, Dimitris VK1SV