- Today, we're going to talk about antenna tuners, a vital,
yet slightly misunderstood ham radio station accessory.
Keep watching to learn more
on the next episode of Ham Radio Q&A.
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Antenna tuners, also called trans matches,
matchboxes, tuning units or antenna couplers,
are devices that match the impedance
from an antenna system to your transceiver.
Amateur radio transceivers expect a 50 ohm impedance
from the antenna, but not all antennas
will deliver that level of impedance.
That's where a tuner comes in.
A tuner typically consists of an inductor
and variable capacitors
that can be adjusted to create the proper impedance.
Now, tuners don't actually tune your antenna.
They don't change the physical characteristics
or make the antenna better,
instead, they just provide the proper impedance match
to the transceiver so the transceiver can operate
in a more efficient manner.
So why do we need one?
Well, basically a tuner gives you more range and utility
from your antenna.
Many multi-band intended designs
will require a tuner for full operation.
Non-resident antennas also require a tuner.
Even if you use a dipole antenna,
a tuner can be used to increase the bandwidth
of your antenna.
For example, if your dipole is resident
on the low end of the band,
a tuner will allow you to work on the upper end of the band.
This becomes necessary, especially in the lower bands,
like 40 and 80 meters,
as an antenna bandwidth typically narrows
as you get lower and lower in frequency.
But what if your transceiver already comes
with a built-in tuner?
Do I still need an external one?
I say the answer is yes.
I believe an external tuner
is an essential station accessory,
even if you don't need it all the time.
Many transceivers do have built in tuning units
but these units are mostly convenience items
as they will only tune to about a 3:1 match.
That means if your antenna is impedance at the feed point
is 150 ohms or is presenting a 3:1 SWR,
the tuner will be able to compensate
for the 50 ohm impedance at the transceiver.
Now that's okay, if you wish to extend your bandwidth
of your dipole or or say you're using a multi-band antenna
like an off-center-fed dipole or end fed half wave antenna.
But you know, you'll get into the lower bands
or use a non-resident antenna, like a G5RV
or anything fed with ladder line,
then an external tuner will be necessary
as these units can give you matches of 10:1, or even more.
A lot of hams will gravitate to external automatic tuners,
and they're nice, I use a couple of myself.
But nothing beats the simplicity and utility
of a good old-fashioned manual tuner.
Manual tuners often will work at higher power levels
or offer an even greater range of impedance matches
than an automatic model.
They're also cheaper than many of the auto tuners,
especially if you find a used one at a ham fest.
Plus, you know, once you set it up
you may even be able to do band changes faster
than an automatic tuner.
But what's inside a manual tuner? Well, let's take a look.
On my bench, I have an MFJ-949D manual tuner.
The 949 series is a very popular and long running tuner
that is still available as the 949E.
I bought this one used, oh maybe 20 years ago.
But really, nothing's changed much between then and now.
Looking at the outside from left to right,
we have the meter.
And this has a cross needle meter
that displays forward and reflected power simultaneously.
You measure the SWR or standing wave ratios
by looking on the graph where the needles cross.
Next, you have a selector switch
to choose between two different antennas.
And there's an antenna bypass switch,
open feed line option, and a dummy load.
So, not only does this unit work as a tuner,
but also provides an antenna switch, a dummy load
and a 4:1 balun for ladder line.
Next are the tuning dials.
The 949 series is a T network tuner
and is capable of matching a wide range of impedance values.
It has three dials,
two for capacitance in one for inductance.
You have the ability to adjust the capacitance
on either side of the inductor.
And basically, you know, that's how tuners work.
All they do is add an amount of inductance and capacitance
to your antenna systems
to bring the feed point impedance down to 50 ohms.
Opening up the tuner, you'll see what I mean.
To the left is the dummy load,
but if you look on the right side of the tuner
you'll see the big air wound coil
that is tapped in several spots.
This is the inductor,
and each tap corresponds to a setting on the inductor dial.
The inductor sits between two air gap capacitors,
one for the transmitter side
and another for the antenna side.
As I turn the dials, the capacitors mesh,
with the least amount of capacitance at the zero setting
and the highest level of capacitance at the 10 setting.
So by looking at how these dials operate,
you can start to get an idea how the tuner does its magic
to adjust the antenna's impedance.
So let's close this up, hook it up to the transceiver
and do some tuning.
I've got the tuner connected to my transceiver
and the antenna I'll be using is a G5RV.
This is a non-resident antenna
that requires an external tuner for effective operation.
So this is a great demonstration of a tuner's ability.
The steps in using a manual tuner are as follows.
First, select your frequency.
You know, find something that's close
to your operating frequency, but don't tune up near or on
an active frequency or where someone is operating.
That's really bad form.
Next, turn your transmit power down to its lowest setting.
This will help protect the transceiver
and limit interference.
Then set your transmitter to a constant carrier mode,
like CW, AM or RTTY.
I usually set mine to the data mode
as then I can use the microphone switch to key the radio.
Next, turn the inductor dial
until you hear a loudest noise level.
Now, this might be a bit subjective
but you'll get the idea of what setting is the loudest.
Never turned the inductor while transmitting.
Now, start transmitting and watch the needles move
as you begin adjusting the transmitter in the antenna dials.
You will want the forward power at its highest deflection
and the a reflected needle at its lowest.
I usually start with the transmitter at the side,
then I'll get that low,
then move to the antenna to bring it down some more.
And then I may finish then by tweaking on the transmitter
and antenna dials a third time.
And that's it.
Once the SWR is at its lowest point,
your antenna's tuned for the transceiver.
After you've tuned it, you can increase your transmit power
and then give it a final test and tweak.
Write these values down in your station log
so you can return to that band and spot easily.
Repeat this process for each band and frequency
you wish to work on
and soon you'll have a list of tuning spots
for super easy operation.
Now, a couple of things to note.
On some bands or frequencies,
you may not be able to get the SWR down to a perfect 1:1.
Depending on the style of antenna you're using,
that's normal and perfectly okay,
as long as you're reasonably below 1.5:1,
the transceiver won't mind.
Also, as I mentioned, the transmitter and the antenna dials
add capacitance to the antenna.
The highest level of capacitance you can give,
the more efficient your tune will be.
So, higher numbers on those dials are better than lower ones
in your overall antenna efficiency.
Finally, antenna characteristics will change
with time and the environment.
Depending on the time of year or the weather,
your tune may change,
so periodic adjustment may be necessary.
That's where we write data down in our station logs
so we can have a reference point for future adjustments.
As a bonus, if you have an antenna analyzer,
you know, such as something like this,
you can use it as your reference signal
and bypass the transceiver.
The process is exactly the same
as tuning with the transceiver.
The analyzer will give you an accurate SWR readings
so you can fiddle all you want with the tuner
without fear of creating interference
or harming the finals in your transceiver.
With a little bit of practice,
you can be a manual tuner pro in no time.
And you'll learn a bit about impedance matching
and see how it is an important part
of an antenna's function.
Plus, isn't it more fun to twiddle dials
then to listen to the quicks and whirs of that auto tuner?
Well, do you have any questions or comments
about using a manual antenna tuner?
Please leave them in the comments below.
I'll filter through the comments
and follow them up on those.
And who knows, maybe yours will end up
on our next Your Questions Answered live stream.
But for more articles and information
and VHF/UHF antennas for sale,
please check out my website at www.jpole-antenna.com.
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That's it for this time.
I'm Michael, KB9VBR, have a great day and 73.