Topband: How Helically Wound Verticals Really Work

[Dan Zimmerman N3OX]

>
> Now as to the question of 80 and 40 meters, that will not work with
> an HWV, but is easily done if a conventional loading coil is used.
> Just change the tap to QSY.  Some advanced systems use a motor
> driven roller inductor to do this.


Even faster is a motor driven tap switch.  Of course, relays can be used but
with a motor driven rotary switch you can easily have 8 different 160m taps,
3 80m/75m taps, and a 40m tap to handle your narrow bandwidths on the lower
bands.

Roller inductor is better for continuous coverage, but QSY from 1820 to 7220
is somewhat slow.

I've been using analog servo loops to control rotary switches (and
capacitors)  for a couple of years now with OK success and a very simple
circuit:

http://www.n3ox.net/projects/servo

http://www.n3ox.net/projects/sixtyvert

There are disadvantages.  The feedback , especially if the feedback pot is
too large, makes the circuit sensitive to getting wet, or the trouble in my
case, getting full of spiders.  Plus it's hard to interface with other
station gear.  I wanted to go over to computer control.

So I'm switching to a stepper motor driven rotary switch instead.  I haven't
uploaded any info on that yet as I'm still working hard on getting it out
under the antenna (and cleaning all the spiders out of the RF components of
the old matching setup).

However, I had good success with the servo technique, the circuit is fairly
simple to find parts for and  build,  and if you use a container that's more
bug-proof than mine it should work just fine for a long time to drive some
ceramic wafer switches for band-switching tasks.

73
Dan