Hi Paul:
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 ?
Actually, BOTH devices may help you. But, at this point, possibly the Antenna
Analyzer might help most... IF you understand what it does.
Using an Antenna Analyzer will allow you to adjust your antenna(s) such that
they will present (to your transmitter) the best and most efficient LOAD for
a given band. The closer the LOAD IMPEDANCE of the antenna (and feedline)
are to matching the output impedance of your transmitter, the more efficient
will be the transfer of RF power from the TX to the antenna. The Antenna
Analyzer is NOT a 'tuning device', in that it MAKES these adjustments! It
only allows you to SEE the effect of adjustments you make to the antenna
as you attempt to optimize the antenna's performance.
On the other hand, an Antenna Tuner (ATU) is a device which you DO
adjust in an
effort to compensate for mismatched presented by the antenna/coax combination
to the transmitter. This device will NOT change the SWR on the coax between
itself and the antenna, BUT it can (often) create an offsetting set of
conditions which will make the mismatch APPEAR TO THE TRANSMITTER is if the
transmitter is seeing a near-perfect load impedance, even though the real
loaf from the antenna/feedline may be much different from 'perfect'.
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 ?
The KAT3 is the 'antenna tuner' of which I wrote above. It is NOT 'the
perfect answer' to all antenna mismatch (SWR) problems. But it CAN compensate
for some of the smaller ones and allow your K3 to operate rather efficiently
into a non-perfect load (from the antenna/coax combination).
You FIRST would want to try to optimize your antenna/coax combination such
that it presents to the TX a LOAD which is as close as possible to the
desired 50 Ohms (which is what most modern ham transmitters wish to see).
Once you have gotten the load from the antenna/coax as close to 50 Ohms as
you can reasonably expect to achieve, THEN, you can use the antenna tuner
(KAT3 or other similar device) to provide the final compensation between
the antenna/coax and the TX so the TX 'sees' its desired 50 Ohm load on the
desired band and frequency.
If your antenna/coax combination cannot present a decent load to the TX, the
antenna tuner will ATTEMPT to compensate so the TX still thinks it's seeing
a workable load impedance. But most ATUs have their limits to he range of
load mismatch for which they can compensate... often they cannot make a silk
purse from a sow's ear!!!
This having been said... and assuming the ATU is either installed INSIDE the
radio, or immediately outside the radio in the coax line, you must understand
that the ONLY compensation which the ATU can provide is to the TRANSMITTER
and any short length of coax between the ATU and the TX. IT DOES NOT CHANGE
THE LOAD (SWR) WHICH IS STILL PRESENT ON THE COAX GOING TO THE ANTENNA! As a
result, if your antenna is badly non-resonant, and presents a horrid load to
the TX, using an ATU may(!) be able to compensate to the point that the TX
'thinks' is sees a resonant antenna, BUT the truth of the matter is that the
TX is the only one being 'fooled'... the antenna/coax still has the same poor
load impedance it originally presented, and it will be just as INefficient as
it was before the ATU was introduced into the equation. The ATU does NOTHING
to change the real matching at the antenna. YOU must make those changes
yourself BEFORE you try to use the antenna.
Where does the "baluns" come into this play with either unit?
A balun (BALanced-to-UNbalanced) impedance transformer will NOT come into play
in the scenario you write about, above. The Buddipole does NOT require an
impedance matching transformer, and neither does the coax between it and
your K3.
Sometimes a 1:1 impedance ratio balun is used in an effort to keep RF which
can appear on the OUTSIDE of the feedline coax from being radiated. In this
case, the 1:1 balun (or a similar in-line coaxial RF choke) will be installed
AT the feedpoint of the antenna. In this manner, RF is 'choked' off of the
outside of the coax and prevented from being radiated, thus keeping the feed-
line from acting as a 'radiating' part of the antenna system.
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.
Hope this helps.
73,
Tom Hammond N0SS
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