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Steve, why do you want to know the instantaneous forward and reflected
power? You really wouldn't need this to implement an effective SWR
protection function, unless you expect that your SWR varies extremely
rapidly which probably is not the case. It should suffice to use one A/D
converter and measure the forward and reflected power at different times and
then do the math. For instance, measure the forward power 10 times at
32us/sample. Then measure the reflected power 10 times at 32uS per sample.
Then average all the forward samples, and the reflected samples for a solid
measurement. Now do the math:
SWR = (1+SQRT(Pr/Rf))/(1-SQRT(pR/pF))
Trip the relay if the SWR is too high.
The whole operation could be performed in less than 1ms.
--Dave
K0QE
> -----Original Message-----
> From: Steve [SMTP:ve3tu@rac.ca]
> Sent: Friday, December 01, 2000 10:03 AM
> To: amps@contesting.com
> Subject: [AMPS] SWR Protection
>
>
> Talking about more interesting aspects of amps, I was wondering if
> anyone knows of a single chip microprocessor or pic that has 4 or 8 A/D
> converters in the chip that can monitor 4 input simultaneously. I am
> planning on building a swr protection board for a solid state amp using
> a 68hc11 chip that has a single A/D converter that has selected inputs.
> It takes 32 micro seconds to do each conversion so you don't really get
> a snapshot of the forward and reflected power at the same time. I know
> the you can fudge it with software and get it close but I an interest in
> simultaneous reading on the A/D input or a simple outboard A/D chip
> would do.
>
> tu es 73 Steve VE3TU
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
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<TITLE>RE: [AMPS] SWR Protection</TITLE>
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<BODY>
<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">Steve, why do you =
want to know the instantaneous forward and reflected power? You really =
wouldn't need this to implement an effective SWR protection function, =
unless you expect that your SWR varies extremely rapidly which probably =
is not the case. It should suffice to use one A/D converter and measure =
the forward and reflected power at different times and then do the =
math. For instance, measure the forward power 10 times at 32us/sample. =
Then measure the reflected power 10 times at 32uS per sample. Then =
average all the forward samples, and the reflected samples for a solid =
measurement. Now do the math:</FONT></P>
<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">SWR =3D =
(1+SQRT(Pr/Rf))/(1-SQRT(pR/pF))</FONT>
</P>
<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">Trip the relay if =
the SWR is too high.</FONT>
</P>
<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">The whole operation =
could be performed in less than 1ms.</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>
<BR>
<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">Steve [SMTP:ve3tu@rac.ca]</FONT>
<BR><B><FONT SIZE=3D1 FACE=3D"Arial">Sent: </FONT></B> <FONT =
SIZE=3D1 FACE=3D"Arial">Friday, December 01, 2000 10:03 AM</FONT>
<BR><B><FONT SIZE=3D1 =
FACE=3D"Arial">To: </FONT></B> <FONT SIZE=3D1 =
FACE=3D"Arial">amps@contesting.com</FONT>
<BR><B><FONT SIZE=3D1 =
FACE=3D"Arial">Subject: </FONT>=
</B> <FONT SIZE=3D1 FACE=3D"Arial">[AMPS] SWR Protection</FONT>
</P>
<BR>
<P><FONT SIZE=3D2 FACE=3D"Arial">Talking about more interesting aspects =
of amps, I was wondering if</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">anyone knows of a single chip =
microprocessor or pic that has 4 or 8 A/D</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">converters in the chip that can =
monitor 4 input simultaneously. I am</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">planning on building a swr protection =
board for a solid state amp using</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">a 68hc11 chip that has a single A/D =
converter that has selected inputs.</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">It takes 32 micro seconds to do each =
conversion so you don't really get</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">a snapshot of the forward and =
reflected power at the same time. I know</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">the you can fudge it with software =
and get it close but I an interest in</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">simultaneous reading on the A/D input =
or a simple outboard A/D chip</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">would do.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">tu es 73 Steve VE3TU</FONT>
</P>
<BR>
<P><FONT SIZE=3D2 FACE=3D"Arial">--</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">FAQ on =
WWW: &n=
bsp; <A HREF=3D"http://www.contesting.com/FAQ/amps"; =
TARGET=3D"_blank">http://www.contesting.com/FAQ/amps</A></FONT>
<BR><FONT SIZE=3D2 =
FACE=3D"Arial">Submissions: &nb=
sp; amps@contesting.com</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">Administrative requests: =
amps-REQUEST@contesting.com</FONT>
<BR><FONT SIZE=3D2 =
FACE=3D"Arial">Problems: =
=
owner-amps@contesting.com</FONT>
</P>
</UL>
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