I believe I have considered nearly every one of the
ideas presented below (except the hardwood boiled
in paraffin :-) I even started to build some
of the solutions, but ran into various roadblocks.
What I eventually decided on is a nylon threaded rod
driven by a screwdriver motor. A movable armature with
female threads moves along the threaded rod and
holds spring loaded gold plated pogo pins that slide on
a gold plated PC board, metallized only near the top.
The PC board gold area is connected to the upper antenna element.
The armature is connected to the lower antenna element
by a wire that hangs down. Limit switches are used at the
top and bottom to stop the motor. Due to the sliding
contacts, there is some tolerance as to where the
motor stops at the top. This system allows me to get
a 1 foot conductor free gap when the switch is open. This
greatly reduces coupling capacitance in the off state.
I am slowly getting this system together as time permits.
Rick N6RK
> Several things come to mind using sliding metal collars or coaxial tubes
> with spring-finger-stock contacts (like the coil-shorting structure in a
> screw-driver-antenna) that could be mechanically positioned to connect/
> disconnect the various sections.
>
> The mechanical driver could be:
>
> - pulley-rope driven where the conducting collar has enough
> weight to allow
> gravity to position it across the junctions with rope pull-back
> disconnect.
> This would be external to the conducting sections and could jam during
> freezing WX if rainwater was present in the sliding gap.
>
> - again a sliding collar with spring-finger-stock inside the
> vertical pipes
> and
> held in position in the upper-section by a spring. A rope exiting from
> the
> bottom could pull the sliding tube-contactor down to connect
> the sections
> together. This would be a weather-proof installation and most
> likely free
> from frozen water jamming.
>
> - a pressure or vacuum driven plunger - or a motor-driven screw - to
> position
> an internal sliding switching collar or a coaxial combination of a
> finger-stock
> lipped-pipe receiving an insulator-led section of smaller conducting
> tubing. The
> insulating guide section could be a section of hard-wood stock
> boiled in
> paraffin
> or Teflon partially inserted inside the sliding contact.
>
> 73 de Dick - W7WKR
> Stehekin, WA
>
>
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