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<p>Scott, your reference suffers from a fundamental design fault:
The balun between the LC network and the symmetrical input port
will not work as expected or provide suffient common mode
rejection (> 30 dB) on the 50 ohms coax side. The balun needs
for efficiency a constant Z. Either you spend a symmetrical LC
network or let a unsymmetrical LC combination float. But in each
case the balun has to be placed at the 50 ohms side.</p>
<p>BTW bidirectional couplers with 5 octaves bandwidth are available
from different manufacturers and vendors. Keep in mind that the
directivity of the coupler should be > 20dB.</p>
<p>73, Helmut, DC6NY<br>
</p>
<div class="moz-cite-prefix">Am 04.11.2020 um 04:31 schrieb Scott
Traurig:<br>
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<pre class="moz-quote-pre" wrap="">***** High Performance Software Defined Radio Discussion List *****
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<div>There are plenty of examples of how to do this. Building
the requisite coupler is not difficult. You can buy them from
Xtronic.</div>
<div><br>
</div>
<div>Here's a more relevant example: <a
href="https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1191&context=eesp"
moz-do-not-send="true">https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1191&context=eesp</a></div>
<div><br>
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<div>Incorporating something like a NanoVNA into this design,
and changing the software to calculate the required L and C
directly instead of iteratively should be possible.</div>
<div><br>
</div>
<div>This could also be accomplished using a link coupled
topology if you prefer.</div>
<div><br>
</div>
<div>73,</div>
<div><br>
</div>
<div>Scott/w-u-2-o</div>
<br>
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<div dir="ltr" class="gmail_attr">On Tue, Nov 3, 2020 at 2:38
PM <<a href="mailto:radio@netins.net"
moz-do-not-send="true">radio@netins.net</a>> wrote:<br>
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<div
style="font-size:10pt;font-family:Verdana,Geneva,sans-serif"><br>
Using SWR is done when tuning L networks, but would like
to try adding stepper motors to a Johnson Viking Matchbox
so I can use it.<br>
<br>
I can't seem to come up with a method to tune for minimum
SWR. I suppose one would adjust first the tuning and step
the loading one way or the other and use the low SWR
position to hold for the next iteration. Then repeat that
process over and over.<br>
<br>
I have been told it is quite difficult to make a
directional coupler that works well over the 160 - 6m
range, but a calibration file could be made at the antenna
system feed point (input side of Matchbox) that might get
a close enough calibration to use for tuning. <br>
<br>
John, W0GN<a
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rel="noreferrer" target="_blank"
style="font-family:Arial,Helvetica,sans-serif;font-size:small"
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