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A Yagi antenna’s resonant frequency is determined by the length of its driven element, reflec-
tors, and directors, as well as a variety of other factors. Since every installation is different, the
factory default lengths in the controller for each band/frequency are almost guaranteed to need
adjustment for your particular installation. Because of this, it is mandatory to tune the length
of the elements on all frequencies of operation before application of high power.
This is done by pressing “Setup” and selecting the “Create/Modify” menu. In this menu, the op-
erator can scale the antenna up or down in frequency by using the “Band Correction Factor” or
adjust the length of the driven element (DVR/DE) until the minimum SWR dip is at least below
1.4-1.3. An antenna analyzer (Vector Network Analyzer) is extremely helpful for this task as it
allows the user to plot SWR over a frequency range, at which you can match the SWR dip in the
antenna with the frequency which you are tuning in the create/modify menu. If you are unable
to make a good match by scaling the antenna or adjusting the length of the driven ele-
ment, you most likely have an issue with your connections or wiring.
SteppIR antenna tunes are broken up into “segments” which we use to create an ideal antenna
at a specific frequency. Each segment consists of a frequency, element lengths, and some mis-
cellaneous display settings like gain, F/R, and beam width. To get the element lengths at fre-
quencies in between segments, the controller utilizes an algorithm to calculate them with the
given segment information. The controller can only “store” lengths at the start of each segment,
and it calculates the lengths in between. What this means for the end user is that the anten-
na can only be tuned once in between each segment.
Important notes:
• Start tuning by first calibrating the antenna.
• You will want to tune starting at the highest frequency and work your way down to lower fre-
quencies.
• Send the antenna to the recommended tune frequency, scan a large span (the SWR dip may
be outside of the ham band) with your antenna analyzer and find the minimum SWR. If it is
below 1.4:1, but the minimum SWR frequency does not match your controller frequency,
then use the band correction factor to scale the antenna up or down in frequency. The band
correction factor should only be used as a tool to find the correct element lengths. Once you
have found a correction factor that lines up the minimum SWR to the controller frequency,
record the element lengths for each element. Set the correction factor back to 0.0% and in-
put the previously recorded lengths into each element. The SWR dip should be back to
where it was when you found the correction factor that works for that segment.
• If the SWR dip minimum is above 1.4:1 you will want to change the length of the active driv-
en element (not always DVR on antenna’s that have relay switching, reference the manual
for the correct active driven element). Lengthen/shorten the active driven element until you
have a SWR minimum below 1.4:1. You will then want to use the band correction factor to
scale the antenna as described above.
• In order to save a setting in the Create/Modify menu, you can simply exit from the screen by
pressing “Setup” again, and when the controller prompts you whether you want to save your
changes make sure you select “Yes” to save your changes.
On the next pages are lists of the segments, segment frequencies, and recommended
tune frequencies for the 2 Element Yagi on the OptimizIR and SDA100 controllers.
HOW TO TUNE YOUR YAGI (MANDATORY)
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