On 1/1/2016 8:16 AM, K4OWR wrote:
:::: Does anyone recall that I originally asked about this?
http://www.dxengineering.com/parts/dxe-160va-1?seid=dxese1&gclid=Cj0KEQiAno60BRDt89rAh7qt-4wBEiQASes2tUOULTlQpNyMARBk4ZWRxw70jODW_FJCuBJ1Td47YMgaAhgQ8P8HAQ
BILL K4OWR
I looked at the data sheet on this and my intuition
told me the top hat didn't make sense either electrically
or mechanically. I did some quick and dirty
modeling with EZNEC over perfect ground and
got a drive impedance around 6-j34 at 1.83 MHz. I
then deleted the horizontal skirt wires and pulled
out the 39 foot top loading wires to a 45 degree angle.
I then got a drive impedance of around 8-j9.
A rope tied to the guy anchors in the manual works
perfectly to do this. These hybrid wire/ropes then
become top guys. Its almost as if this was the original
design, and then they wanted to make a fancy top
hat. The data sheet brags about the
uniform current in the vertical, but this simplified
version kept the current within +/-7%. Good enough
for me. I don't have a mechanical modeling program,
but I don't like the DXE design in that respect either.
It doesn't lend itself to a falling derrick erection
method, so you have to use their patented winching
fixture and bolt it to a concrete base. It seems like
this is the hard to way to build a vertical.
I needed an emergency 160 meter vertical a few years
ago and I made a 60 footer out of 2 30' long
3" diameter irrigation pipes with 2 top loading
wires pulled out. A third pipe was used as a
falling derrick. Pretty simple and it worked great.
Rick N6RK
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