Topband: Remote coax switching

[Tom Rauch]

> Reading all the posts about cores and their problems, I'm wondering why
> nobody is talking about using remote transistors to switch the relays.

Hi Larry,

I was concerned we might get to a point where everyone worries about cores.
Cores aren't really problematic, at least not so far as I can tell by
anything I have measured, unless they have a high ampere-turn winding
without a opposite current winding canceling the flux. Of course I would
never want to pass a few hundred milliamp-turns of current through a small
high-permeability core's winding while it is operating. I certainly can't
claim this means every core is problem free. I only tested the cores I use.

Solid state devices are generally a problem with close-by lightning hits,
although I used to have a box with a single cable feed that did all
switching with audio tones and ran 48VAC down the coax for power, rectifying
and filtering the dc at the remote box where it ran CMOS logic, relays, and
even preamplifiers.

I now use conventional DIP relays with telco cables from logic lines, and
switch three groups of antennas 8 directions using just 9 wires. The longest
control distance is 2500 feet. There isn't a semiconductor in the control
wiring beyond a barrier of isolation relays at the house entrance. Even the
amplifiers are in the house.

73 Tom