In the late fall of 1998, my interests in dx turned towards the world of lowband dxing. I put up a simple inverted
L antennna with about 20 radials of about 20' each. The major part of the L was horizontal, not a great 75M dx antenna, but
I did work out.
Well, after reading many books and articles, I decided that a vertical would be my answer. I have a small backyard.
Its wide but shallow. Using a few lengths of aluminum tubing I had in the garage and I puchased a few more 6 ft lengths, Version
# 1 was born. Since the vertical was short, approx 26 feet, a base loading coil was needed. So, using #8 copper, the coil
was wound. To maintain a high Q and keep losses low, a Length to Diameter was to be 2:1. Finding and stripping old data cables
provided me with lots of radial wire. There we go.
When trying to load my transmitter to the vertical, the lowest SWR was approx 1:9 to 1. Puzzled, I remembered that a
vertical was approx 1/2 of a dipole, thus a base impedance should be approx 30 ohms.Ah, needs a matching network of some sort.
So, a small coil was wound from #14 wire, approx 3" L and 1.5" D. Bingo, by adjusting the loading coil for resonance(by compressing
or expanding) and the matching coil for SWR, a bandwidth of 180 Khz between the 2:1 to 1:1.2 swr range became reality.
Version #2 I removed both coils and tried linear loading. Well, it didn't quite work the way the theory books talked
about. I still needed a matching coil, so on to Version 3.
This time, I added another few feet of alum tubing and constructed a top hat. Basically two 6' lengths of
thin alum tubing forming a large X at the top of the vertical with #12 wire forming a circle around the edges of the X. I
also added more longer radials. The total number of radials is now 46. This one works great! I guyed it midpoint using 4 ropes.
It does bend in the strongest winds, but still stands tall.
On a final note, I take this vertical down in the spring and put it back up in the fall, radials and all! This unfortunatly
is because of my small back yard and the tree and lawn people that would get tangled up in the coax, radials and guy
ropes. Oh well, maybe next qth will have more property that could be sectioned off for more antennas and towers!! I would
like to try top band one day!
View the pictures and write me for any more details. It was a fun and easy project!
See you in the window!