[AMRadio] Correct tuning procedure


Mike Dorworth, K4XM k4xm at arczip.com
Thu Apr 20 19:20:58 EDT 2006


----- Original Message -----
From: "gwt" <gwt at mpinet.com>
To: "AM Radio List" <amradio at mailman.qth.net>
Sent: Thursday, April 20, 2006 6:07 PM
Subject: [AMRadio] Correct tuning procedure


> Hi,
> I'm wondering if some "guru" out in AM land can set me straight on how
> to properly tune a long wire using an "L" network or a "T" network tuner
> configuration. I have two
> long wires, each 285 feet long. They feed directly into my shack, where
> the tuner is located.
> I have a tuner that I built using a BC610 external tuner roller inductor
> and two BC610 variable capacitors, allowing me to use either method to
> tune my long wires.
> Question #1:
> Which is the best method to tune with? An "L" network or a "T" network?
> Question #2:
> To reduce the losses coming from the tuner, which is best to use? The
> least amount of
> inductance you can use to get a match, or the highest inductance to get
> a match?
> Question #3:
> Which method will most likely give the widest bandwidth without re
> adjustment?
>
> Thanks,
> George KE4HJ


  http://fermi.la.asu.edu/w9cf/articles/tuner/tuner.html
First go read this article. To answer the questions the "L" is  best by a
factor of 7. The L must be turned around to match either high or low but is
always the most efficient. The "T" is just two "L's" back to back. This
gives many chances to mistune. The correct tuning of the "T" is to set the
capacitors at maximum capacity and use the inductance that lets the match be
with maximum capacity, especially on the output side. i.e. the first dip
from the minimum side of the coil. The loss is only in the coil and  lots of
loss will widen the match by placing resistance in parallel. In the split
stator parallel coil tuner it is the opposite. Use the minimum capacity and
max coil for lowest Q which will allow the match. Hope this helps. After you
study the link story from QEX you will be able to do your own math and
measurements and take NO One's word..There is so much misinformation around.
. If you don't have Walt Maxwell's "Reflections" get it!.. 73 Mike




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