I just completed a new antenna and made some before and after measurements
with K5NA about 22 miles away.
Old antenna:Long Inverted-L matched with a capacitor. Height at bend was
118 feet; 7 elevated 130 foot radials up about 15 feet.
New antenna: 4-Square made from 4 ground mounted Inverted-Ls that go up 55
feet and then go horizontally back to the supporting tower. Comtek coupler.
Each has 60 100 foot radials with the typical bus bar arrangment at
crossover points to keep radial currents within its quadrant. I would have
liked to make the radials longer and the antennas higher but both were
constrained by the lot...
We tried before and after measurements on the old antenna with and without
the new radial system to see what effect this had as a ground screen.
Unfortunately, we decided after the fact that we should have set the signal
for a level of flicker on his LED based S-meter so really can't say much on
this result.
So the "old antenna" measurement used to compare with the new antenna had a
ground screen of sorts - the old antenna was in the plane of two of the new
antenna so had at least a 0.2 wavelength screen in the closest to the edge
direction.
The new antenna measures 11 dB louder at K5NA than the old antenna. Now
how much of this is from other factors, I don't know but this is 5dB more
than expected with the 4-Square. The antenna seems to be playing quite
well in all directions with good F/B in each quadrant so I do not attribute
this result to a funky pattern...
By the way, we were messing around and managed a QSO at 60 microwatts for
better than 350,000 miles per watt!!
Tom N5TW
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