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Read AR510 Tom (at least read the title), Helge did NOT think the same thing
as you. Your argument and his are the exact opposite. Please get your facts
straight. I'm done.
Dave
K0QE
> -----Original Message-----
> From: Tom Rauch [SMTP:w8ji@contesting.com]
> Sent: Tuesday, December 05, 2000 9:01 AM
> To: amps@contesting.com; Dave D'Epagnier
> Subject: RE: [AMPS] SWR Protection
>
> > Tom, I think you've been fooled all this time about the most common
> > failure mode of solid state transistor amplifiers. Again, the main cause
> > of failure is excess power dissipation in the transistor due to load
> > mismatch, not voltage breakdown. If voltage breakdown were the issue,
> > you'd see voltage peak detection circuits in amp finals.
>
> If I was fooled, so was Helge Granburg at Motorola before he died.
>
> Helge, being fooled like me, thought the same thing.
>
> The reason you don't see peak voltage detection circuits is
> because by the time the voltage gets there, it is too late. You will
> never remove drive in less than a few RF cycles.
>
> That's why you need to measure SWR, and do it while the
> envelope is rising....unless you use transistors that have a voltage
> rating of several times the working voltage or use a hard clamp that
> is very fast.
>
> Of course you could be right, and Helge could have been wrong.
> But keep in mind I can measure hundreds of volts on the drain of a
> MRF-150 operating at 20 volts with the right load conditions.
>
> 73, Tom W8JI
> w8ji@contesting.com
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<TITLE>RE: [AMPS] SWR Protection</TITLE>
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<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">Read AR510 Tom (at =
least read the title), Helge did NOT think the same thing as you. Your =
argument and his are the exact opposite. Please get your facts =
straight. I'm done.</FONT></P>
<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">Dave</FONT>
<BR><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">K0QE</FONT>
</P>
<UL>
<P><FONT SIZE=3D1 FACE=3D"Arial">-----Original Message-----</FONT>
<BR><B><FONT SIZE=3D1 FACE=3D"Arial">From: </FONT></B> <FONT =
SIZE=3D1 FACE=3D"Arial">Tom Rauch [SMTP:w8ji@contesting.com]</FONT>
<BR><B><FONT SIZE=3D1 FACE=3D"Arial">Sent: </FONT></B> <FONT =
SIZE=3D1 FACE=3D"Arial">Tuesday, December 05, 2000 9:01 AM</FONT>
<BR><B><FONT SIZE=3D1 =
FACE=3D"Arial">To: </FONT></B> <FONT SIZE=3D1 =
FACE=3D"Arial">amps@contesting.com; Dave D'Epagnier</FONT>
<BR><B><FONT SIZE=3D1 =
FACE=3D"Arial">Subject: </FONT>=
</B> <FONT SIZE=3D1 FACE=3D"Arial">RE: [AMPS] SWR Protection</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">> Tom, I think you've been =
fooled all this time about the most common</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">> failure mode of solid state =
transistor amplifiers. Again, the main cause</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">> of failure is excess power =
dissipation in the transistor due to load</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">> mismatch, not voltage breakdown. =
If voltage breakdown were the issue,</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">> you'd see voltage peak detection =
circuits in amp finals.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">If I was fooled, so was Helge Granburg =
at Motorola before he died.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">Helge, being fooled like me, thought =
the same thing.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">The reason you don't see peak voltage =
detection circuits is </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">because by the time the voltage gets =
there, it is too late. You will </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">never remove drive in less than a few =
RF cycles.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">That's why you need to measure SWR, =
and do it while the </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">envelope is rising....unless you use =
transistors that have a voltage </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">rating of several times the working =
voltage or use a hard clamp that </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">is very fast.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">Of course you could be right, and =
Helge could have been wrong. </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">But keep in mind I can measure =
hundreds of volts on the drain of a </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">MRF-150 operating at 20 volts with =
the right load conditions.</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial"> </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">73, Tom W8JI</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">w8ji@contesting.com</FONT>
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