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Use an Antenna Tuner
Get maximum power to
your antenna by learning how to hook up
and use a tunner to
properly "trick" your rig!
Yes, "TRICK" YOUR
WHAT IS AN ANTENNA
You have to learn how to
hook them up to your tranceiver properly and tune them correctly to
make your radio "think" that it is
feeding it's signal into a "perfect or near perfect 50 ohm laod
called your antenna!
tuner, (transmatch), doesn't really TUNE your antenna OR ANY PART OF
What an antenna tuner or transmatch does do, however, is
transform the impedance at the antenna feed output at the radio to a
value that your transceiver can handle, (typically 50 Ohms).
thinking about antenna tuners and SWR, it's important to remember
that the tuner has no effect whatsoever on the SWR
between itself and the antenna.
It's the SWR between the
transmitter and the tuner that is changed with the tuner
In layman's terms, all a tuner does
is act as a kind of adjustable impedance transformer between the
radio and the antenna. It takes whatever impedance the antenna
system presents, up to the design limits of the tuner, and attempts
to convert it back to 50 Ohms--or something reasonably close to that
value for the transceiver. When the transceiver "sees" a 50 Ohm
impedance, it is able to load or produce it's maximum designed RF
output into the system because it is designed to operate into a 50
Your rig "thinks" it's seeing a 50
ohm antenna on it's output!
That power is transferred through the antenna tuner, to the
feed line and, ultimately, to the antenna--minus
any losses incurred along the way.
If you have high loses and a
poor excuse for an antenna, you will have a poor excuse for a good
signal no matter how well your tuner "tricks" your radio.
the power will be lost as heat in the tuner and very little will get
to the other station!
These losses are the reason that the highest efficiency
feed-line for each individual case is desirable and why some
amateurs use ladder line on HF, which has the least loss per foot,
which means maximum power at the input terminals of the
HOW TO HOOK UP AND
So now that you have a better understanding of what an
antenna "tuner" actually does, let's hook one up in a typical HF
In the block diagram below we have typical Hf
station setup consisting of, from lert to right,:
A Linear or power amp
Low Pass Filter
The Antenna Tuner
A Dummy Load
IMPORTANT PART......THE ANTENNA!
Take a look at the block diagram above and notice
where the antenna tuner and SWR meter are in relation to the flow of
the RF signal coming from the transceiver. (Note that the rf is
actually flowing in both directions and not just toward the
PLEASE DISREGARD THE LINEAR AND LOW PASS
FILTER FOR THE MOMENT! (Your station may not use
will notice that.... first, from left to right, you have the
transceiver, Swr/watt meter, ANTENNA TUNER and then the antenna on
The rf moves from the transceiver to the SWR/WATT
meter, then finally thru the "tuner" and out to the
You just learned
how to hook it all up! Just remember that our goal is to make the
transceiver think all is well, and in order to "read" the SWR and
Power out pertaining to "all is well"......at the radio's
output....the swr meter must be between the
radio and the tuner. NOT ON THE ANTENNA
Now Let's learn how to "tune" that
Most antenna tuners have an inductance rotary switch
and two capacitors. (refer to photo at top of page) The capacitors
are often labeled ANTENNA and TRANSMITTER. In some antenna tuners
the inductance switch is replaced with a continuously variable
inductance, popularly known as a roller inductor.
Let's assume you're
using a tuner with an inductance switch, because they are the most
SHOCK HAZARD! NEVER TRANSMIT
WITH THE TUNER COVER OFF AS IN THE NEXT STEP!
TURN OFF THE POWER
TO THE RADIO!
Place both capacitor controls
at their mid-range positions. Don't trust the knob markers if this
is your first experience with the tuner! If you are
comfortable with the next procedure, remove the cover of the tuner
and turn the knobs until the moving capacitor plates are only half
meshed with the stationary plates. If the knobs are pointing to half
scale with the reference markings on the knobs and front cover,
consider yourself lucky.
If not, loosen their Allen screws and
rotate the knobs so that they point to mid scale.
knobs, replace the tuner cover and you're ready to go.
Turn the radio on and tune receiver to an
un-used frequency on the band you desire, listen for a few seconds, with
the antenna and transmitter controls at mid scale, move the
inductance switch to each of it's positions until you hear the
loudest noise or signals coming into your radio. Then, rotate the
antenna and transmitter controls until you get to the absolutely
loudest noise or signal level on the radio. All three of these
controls interact with each other so practice on several bands to
get the "feel" of the procedure.
Select your final band of
operation and repeat the procedure above. When noise peaks out using
your ears and the S meter, your tuner settings should be very close
for final operation.With your rig set to low power monitor the
frequency to assure that it is not in use, send your ID then
transmit a continuous carrier while you tweak the antenna and
transmitter controls for the lowest reflected power reading with the
highest output power as read on the Swr/Watt meter. You may find
that you have to vary the position of the inductance switch a
position or two either way to get your best match.
Play it safe
and un-key before turning the inductor switch...un-key
first....turn the switch...key up....repeat as needed until
lowest SWR and maximum output. Be gentle to your radio; keep the
key-down periods as short as possible. Depending on the impedance at
the antenna input (and the overall design of the tuner) you may not
be able to obtain a flat 1:1 SWR on all frequencies and
Also important to remember is that your Swr will change,
go up, as you tune further away from the frequency you used to
"trick" your radio! So re-check and re-tune as needed as you move
around the band.
You can get an idea of your SWR bandwidth by
starting with your original frequency, and using the procedures
above withlow power, (don't move any knobs or switches after best
setting)....sweep or tune your VFO up and down the band while
watching the SWR readings and note the frequency where the SWR
reaches 2:1 at the higest and lowest frequency. Stop
If your on
40 meters at say...7.262mhz as your starting point, and your SWR is
2:1 at 7.292mhz and the highest swr going the other way is 2:1 at
7.259mhz, then your "safe tuning range" without retuning the antenna
tuner would be about 60khz.
Keep in mind to use very low power
and ID because your signal may be heard for a split second as you
tune across the band! When that transmit key is down, someone
somewhere can hear you. Even a dummy load gets out
Remember your "TRICKING" your way around a good
So what kind of tuner
should I buy?
Click on the ad below to see the latest
ARRL Book "A Guide to Antenna Tuners"
with information for choosing the right tuner for your ham radio
New! from the
The Guide to Antenna Tuners!
A must have for all
hams who need more information!
In reality, there is no
"tricking" involved anywhere and we were playing with words
here like "tricking, fooling", etc.
It is useful to employ a
matching device, the antenna tuner, between the transmitter and the
antenna feeder when antennas with complex impedances are used.....
so the transmitter will "see" a 50 -52 ohm load even though a
significant mismatch is present at the antenna feed point. The
tuner, matchbox or transmatch as it is sometimes called,
will not correct the actual SWR condition on the
feed line OR antenna, but it will resonate the antenna system
as a whole that the radio "sees" on
it's output and allows the transmitter to
deliver as much power to the antenna system as possible
within the design parameters of the tuner. The transmitter now can
produce it's rated power out to the tuner in the
hopes that the tuner can do it's job and get most of that power into
the antenna system with some efficiency.
line: Your transmitter will not
know that you are trying to "load up" those old rusty bed springs or
that poor excuse for an antenna! Just
because you're now seeing that "magic" 1 to 1 VSWR reading on the
meter does not mean you have changed the design of those old rusty
bed springs or whatever you're trying to us as an antenna!!!
The more efficient your
antenna system.....the better!
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