I'm not surprised and the results seem reasonable.
Wes N7WS
On 12/8/2018 2:07 PM, MICHAEL ST ANGELO wrote:
Now that the leaves are off the trees and the cold weather has returned it's
time to do antenna work.
I have an inverted L between two trees with 34 radials on the ground. Four
radials are 135 feet long, the rest 70 feed long. I choose these lengths
because they fit my yard. During the summer I keep the radials in the wooded
area of my property in an arc of about 210 degrees. Once the leaves are off the
trees I spread the radials into a full 360 degrees.
I normally measure the feed impedance with my N2PK VNA with requires lugging a
laptop along with me. I built a FA-VA5 Antenna Analyzer. While cumbersome to
used standalone it is battery powered and quite handy.
My Inverted L is longer than a quarter wavelength on 160. I also use it on 80
meters and don't have to worry about matching a high impedance.
I wanted to see what effect changing the radial field diameter. I measured at
the resonant frequency, 160 and 80 meters. Here are my results:
210 degree radial field:
Freq(MHz) Rs Xs
1.62 21.2 -1.7 (close to resonance)
1.8 30.7 +112
2.0 46.5 +237
3.5 111.0 -654
4.0 65.6 -346
360 degree radial field, relocated 7 radials.
Freq(MHz) Rs Xs
1.62 16.7 -5.6 (close to resonance)
1.8 23.6 +107
2.0 36.4 +233
3.5 124.0 -661
4.0 59.7 -351
I wanted to move more radials but unfortunately they are stuck under a frozen
leaf cover. I'll get to these when it warms up.
I was surprised that moving just a few radial made such a difference.
Mike N2MS
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