Date: Wed, 25 Nov 2009 15:23:23 +0100
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
In-Reply-To: <e0d890420911250347q2bd7e758g8662530a47b9d78b@mail.gmail.co
 m>
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 <e0d890420911250347q2bd7e758g8662530a47b9d78b@mail.gmail.com>
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Subject: Re: LF: Class E pa
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Hello Tony,

>I'm still using a Derivative of the Design from G3YXM's class E 1KW TX on LF

If you refer to the TX in http://www.wireless.org.uk/136rig.htm : 
this is a class D TX, not class E.
I am also using a "G3XYM clone" on 500kHz (with a pair of IRFP350's). 
Running on 44V / 7 A it delivers just over 250W, about 82% 
efficiency. It seems very forgiving to mismatch, no FET failures so 
far (fingers crossed). But for testing purposes (antenna tuning) I 
run it on 13.6V (abt. 25W output) where it can handle any mismatch.

73, Rik ON7YD

At 12:47 25/11/2009, you wrote:
>Hi Mal
>I'm still using a Derivative of the Design from G3YXM's class E 1KW 
>TX on LF. Recently I've built a TX for 500 kHz using the same 
>principle. It works great and delivers up to 500W. Unfortunately 
>only into a dummy load, because 500 kHz is still not allowed here in 
>Switzerland. But at least - I will be ready ;-)
>73 de Toni, HB9ASB
>
>2009/11/25 mal hamilton <<mailto:g3kevmal@talktalk.net>g3kevmal@talktalk.net>
>Ref recent discussion on the subject.
>
>I use a class E pa on 500 kcs and never get any trouble.
>As a general guide use high voltage fets and the fet V should be 
>rated at  about 5 times the supply V and current about 3 times.
>You arrive at class E by careful design not by accident.
>Having designed and built the PA for the required power and load R 
>usually 50 ohms adjust into a DL for correct waveform as displayed 
>on a 'scope, this is important otherwise V spikes and instability 
>will kill the fet.
>Install a suitable antenna and match it with a suitable atu to 50 
>ohms so when you connect the TX/PA to the antenna they both match.
>Check the wave form again and any slight mismatch should be adjusted 
>by the antenna atu and NOT the pa.
>The load does not have to be 50 ohms but this is convenient when 
>testing with available test gear.
>High V fets give more realistic C and Inductor and R values. A good 
>range for fets is a psu giving 40 - 100 volts ie fets 500volts and a 
>suitable current rating depending on your power. requirements ie if 
>you need to draw 5 amps the fet should be rated 15 amps.
>These are the general guidelines and work well for me.
>Most amateurs seem to use class D amps whereas class E are rare.
>
>de Mal/G3KEV
>
>

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Hello Tony,<br><br>
<blockquote type=cite class=cite cite="">I'm still using a Derivative of
the Design from G3YXM's class E 1KW TX on LF</blockquote><br>
If you refer to the TX in
<a href="http://www.wireless.org.uk/136rig.htm" eudora="autourl">
http://www.wireless.org.uk/136rig.htm</a> : this is a class D TX, not
class E.<br>
I am also using a &quot;G3XYM clone&quot; on 500kHz (with a pair of
IRFP350's). Running on 44V / 7 A it delivers just over 250W, about 82%
efficiency. It seems very forgiving to mismatch, no FET failures so far
(fingers crossed). But for testing purposes (antenna tuning) I run it on
13.6V (abt. 25W output) where it can handle any mismatch.<br><br>
73, Rik  ON7YD<br><br>
At 12:47 25/11/2009, you wrote:<br>
<blockquote type=cite class=cite cite="">Hi Mal<br>
I'm still using a Derivative of the Design from G3YXM's class E 1KW TX on
LF. Recently I've built a TX for 500 kHz using the same principle. It
works great and delivers up to 500W. Unfortunately only into a dummy
load, because 500 kHz is still not allowed here in Switzerland. But at
least - I will be ready ;-)<br>
73 de Toni, HB9ASB<br><br>
2009/11/25 mal hamilton
&lt;<a href="mailto:g3kevmal@talktalk.net">g3kevmal@talktalk.net</a>
&gt;<br>

<dl>
<dd><font size=2>Ref recent discussion on the subject.<br>
</font>
<dd>&nbsp;<br>

<dd><font size=2>I use a class E pa on 500 kcs and never get any
trouble.<br>

<dd>As a general guide use high voltage fets and the fet V should be
rated at&nbsp; about 5 times the supply V and current about 3 times.<br>

<dd>You arrive at class E by careful design not by accident. <br>

<dd>Having designed and built the PA for the required power and load R
usually 50 ohms adjust into a DL for correct waveform as displayed on a
'scope, this is important otherwise V spikes and instability will kill
the fet. <br>

<dd>Install a suitable antenna and match it with a suitable atu to 50
ohms so when you connect the TX/PA to the antenna they both match.<br>

<dd>Check the wave form again and any slight mismatch should be adjusted
by the antenna atu and NOT the pa. <br>

<dd>The load does not have to be 50 ohms but this is convenient when
testing with available test gear.<br>

<dd>High V fets give more realistic C and Inductor and R values. A good
range for fets is a psu giving 40 - 100 volts ie fets 500volts and a
suitable current rating depending on your power. requirements ie if you
need to draw 5 amps the fet should be rated 15 amps.<br>

<dd>These are the general guidelines and work well for me.<br>

<dd>Most amateurs seem to use class D amps whereas class E are rare.<br>
</font>
<dd>&nbsp;<br>

<dd><font size=2>de Mal/G3KEV<br>
</font>
<dd>&nbsp;<br><br>

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