On 6/21/2020 7:06 AM, VE6WZ_Steve wrote:
This morning I uploaded a YouTube video explaining the method for tuning any
2el parasitic array.
I do some experiments in my workshop using the Nano-VNA on a small 2 el Yagi to
explain mutual coupling. Then using 4NEC2 I show the relationship between the
dip in real R (point of maximum coupling) and the F/B and gain of the array.
Using this understanding any 2 el parasitic array can be tuned with confidence
on the tower by only sweeping the driver with the antenna analyzer. There is
no need to isolated the driven element and do analyzer sweeps on the parasitic
element. This method is especially useful for tuning arrays with non-split or
grounded parasitic or driven elements.
This is the method I used for tuning my 2 el 160m parasitic array that uses the
shunt-fed (grounded) tower as a driver.
https://youtu.be/2DcvmGPLdT0 <https://youtu.be/2DcvmGPLdT0>
73, de steve ve6wz
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You should be able to tune up any 2 element array, whether parasitic
or driven, by simply putting a signal source behind it and adjusting
for max F/B. Or putting the signal source in front and adjusting for
maximum gain. No analyzer required. Then, you can substitute fixed
components for the variable L's and C's if desired. This method works
even if the driven element is a shunt fed grounded tower. Just use
the feed as it was when the tower was just a single vertical.
After doing that, you can get out the analyzer and
measure the drive impedance of the phasing network and design a
simple matching network to go between it and the transmitter.
BTW, parasitic arrays seem simpler, but driven arrays (especially
2 element ones) have better F/B ratio ), and broader bandwidth,
AFAIK. YMMV.
73
Rick N6RK
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