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Author Topic: Reversible L antenna tuner  (Read 3742 times)
WB6BYU
Member

Posts: 13343




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« Reply #15 on: November 22, 2012, 09:18:32 PM »

This was my first time using the new QST archive system, so I was
learning as I went.

Once you register for the ARRL web site and sign in, go here:
http://www.arrl.org/arrl-periodicals-archive-search
and then enter the search information.  I couldn't figure out how to
specify a range of years, so had to search one year at a time.  Searching
for "transmatch" seemed to give better results than "tuner".  You can then
pull up each article of interest as a PDF file.

Have fun!
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AC8KU
Member

Posts: 8




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« Reply #16 on: November 23, 2012, 05:15:44 PM »

Those links and suggestions worked. I've got plenty to read now. Smiley
-John
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WB6BYU
Member

Posts: 13343




Ignore
« Reply #17 on: November 25, 2012, 09:06:28 AM »

A couple further suggestions for a practical implementation:

1) Adding a switchable 4 : 1 (or 1 : 4) transformer on the input avoids some of the issues
with small components when the load is near 50 ohms, because you it allows you to have
the network step it up to 200 ohms or down to 12.5 ohms instead of matching it directly.

2) When using the same antenna for an extended period of time (which isn't that common
in my station - I'm always trying something new) a useful approach is to build a fixed-tuned
tuner.  I found a 3-pole 11-position rotary switch and mounted it on a chassis, allocating one
position for each band (and a couple spares for 80m, etc.)  I build a simple L-network tuner
and found the settings to match my antenna on each band, then built them into the main
box using fixed capacitors or mica trimmers and taps on a series of coils.  One wafer of the
switch selected the input capacitor, one the coil tap, and the other the output capacitor.
Particularly with a tube rig such as the DX-60 you only have get reasonably close to a
match and then tune up the rig.

This took a bit of experimenting to set up initially, but once completed, changing bands was
simply a matter of turning the switch.  You don't need a big roller inductor or variable
capacitor (though I did add a receiver variable to tune across the lower portion of 80m.)
If you don't change your antenna often, you shouldn't need to change your tuner settings
either, and this approach gives you a lot of flexibility in what matching configuration you use
for each band.

Good luck with your experiments!
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