[Elecraft] Antenna Tuner versus Antenna Analizer ?

[Bruce McLaughlin]

I am not totally sure about your question but if you are wondering what the
difference is between an antenna analyzer and an antenna tuner, basically
the analyzer is an instrument to determine the characteristic impedance of
the antenna at the antenna terminals or the characteristic impedance of the
antenna system, including the feed line, at the end of the feed line.  It
can also measure a number of other electrical characteristics and is a very
useful instrument but I think it is probably in excess of your needs at this
stage of your hand career.  And antenna tuner on the other hand is a device
which will attempt to transform the impedance presented to it at the end of
the feed line from the antenna so that it matches the expected load
impedance of your radio which is 50 ohms.  The resulting transformation or
"match" performed by the antenna tuner should result in a 1:1 SWR as seen by
the final of your radio.  When there is a low SWR as seen by the final of
your radio there should be a maximum transfer of RF power from your radio to
the antenna so that it can be radiated as a signal.  However, if there is an
extreme impedance mismatch between the end of the feed line and the 50 ohms
expected by your radio there can be problems as noted below.

I think you will find that the K-3 antenna tuner is a very good one and will
tune a wide range of antennas.  Since you already have it, I suggest you try
it first with your antenna.  If for some reason it does not work you could
always try a different, external tuner.  But if the antenna cannot be tuned
with the built-in K-3 tuner I think you would be well advised to consider a
different antenna.  Just because you may be able to reduce the SWR presented
to the radio by using a tuner does not mean you have an efficient system or
that most of your RF will actually be radiated rather than simply dissipated
in the tuner.

If the terminal match between the antenna and feedline is very unfavorable,
while the tuner may be able to transform the resulting SWR presented to the
radio enough to allow the final to run at full power you may find that much
of the power is being dissipated in the antenna tuner as heat rather than
being radiated by the antenna.  If for example you are running 100 W from
the transmitter but 80 of those watts are being dissipated in the tuner
because of a very unfavorable antenna impedance, there won't be much RF
power left to actually reach and be radiated by the antenna.

So, I would try the K-3 antenna tuner first.  Chances are it will do the
job.  If not you may want to consider a better antenna before you start
looking for external antenna tuners.  Frankly, the only time I would
consider an external tuner is if I were using a balanced feed line and even
then I might choose a 4 to 1 current balin at the output of the radio
instead of a balanced antenna tuner.  Another situation calling for an
external tuner might be if you are using an amplifier following the K-3 and
the impedance presented by the antenna system cannot be handled by tuning
the amplifier.  Good luck with your license upgrade and your new K-3.

Bruce-W8FU

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Paul Maruna
Sent: Wednesday, September 10, 2008 6:47 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] Antenna Tuner versus Antenna Analizer ?

I bought a buddipole antenna system and I want to get one of the subject
units but I don't know the difference between them, and what each one does,
and which one will help me with the setup with my K3 and my antenna system ?

When I bought my K3 I also bought a KAT3 which I believe is an antenna tuner
for the K3 -- Will this do the same thing to match the antenna to the K3, or
am I better off getting another unit like a LDG Z-100 or an LDG AT-200 Pro
or something else like one of the MFJ units ?

Where does the "baluns" come into this play with either unit ?

I am just a Technician class and am studying for the General class and I
have not built the K3 that I have yet, and all this antenna stuff is pretty
confusing.

Can anyone help please ?

Thank you,
Paul
(73)
KD8HWP
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