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Tuning
Using a
good
quality Antenna Analyzer, connect the coaxial cable coming from the NVIS antenna.
40 Meters:
Sweep the antenna for 40 meters to see where the SWR dip is located.
Ideally, you will want the 40 meter dip to be near the lower end or mid range on the 40 meter band.
If you are specifically going to use one frequency, then adjust for that frequency for best results.
If the dip is low, shorten the 40 meter antenna wires equally to raise the frequency dip. If the dip is
high, lengthen the 40 meter antenna wires equally to lower the frequency dip.
With the length described, the test antenna (NVIS-8040S) resonated at 7.261 kHz. The length of
each leg was then lengthened by 3 inches on each side and the measurement was then 7.147 kHz.
This works out to approximately
38 kHz per inch of change
.
When changing wire lengths, wrap the excess wire back on itself rather than
cutting the wire. This will allow for future adjustments that may be needed.
Repeat the sequence above for 80 meters.
80 Meters:
For 80 meters the bandwidth is a bit narrow and physical tuning of the 80 meter wires
may be needed to get in your desired area of the 80 meter band.
With the length described, the test antenna (NVIS-8040S) resonated at 3.410 kHz. The length of
each leg was then shortened by 8 inches, then 3 feet, then 2 feet on each side and the measurement
was then 8.96 kHz. To make it better, it was then lengthened by 4.8 inches, which brought the
resonant point to 3.972 kHz. All of this worked out to be
8.95 kHz per inch of change
.
Once the antenna is
tuned, you can
connect the coaxial
cable to your
transceiver for
operation. Modern
transceivers that
have an internal
tuner should be able
to perform ‘touch-
up’ tuning easily on
this antenna.
Typical 40 meter
and 80 meter SWR
sweeps using a Rig
Expert antenna
analyzer:
