Topband: Anybody?

[Richard (Rick) Karlquist]

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