> I avoid that by using a DPDT relay in a "transfer"
configuration. The
> base of the vertical goes to one pole and the other pole
goes to the
> feedline center conductor. A jumper runs across the two
N.C. contacts
> and the loading coil runs across the two N.O. contacts.
On 80m the
> relay is not energized and the feedline connects directly
to the
> vertical base through the jumper.
I may be missing something, but I don't get it.......
You still have the full 160 meter vertical's base voltage
from one contact to ground when on 160. You have full
loading coil voltage across the two contact bars, and across
two open contact air gaps through the shorting strap.
Worse yet, you now have full vertical base voltage on 160
across the contact bar-to-armature insulation, and that is a
notoriously weak point in relays!!!
As a matter of fact, if you simply tied the 160 coil
directly from the vertical base to the coax center and
shorted it with the relay moving contacts, you have exactly
the same voltages at every point in the system.
If it was my relay system, I'd tie the 160 coil across the
stationary contacts, either the NO or NC pair depending on
the control logic. I'd place a short between the moving
poles. This way, when the 160 coil is in and the voltage is
highest, there is no voltage directly on the moving contact
bars. Virtually all relays would "like" that wiring better.
Moving bar voltage would be much lower, and contact voltage
would be no higher.
This relay switching of loading coils is a paradox. There is
no way to not have nearly full loading coil voltage across
some close gap in the relay. As a general rule, you are
better off keeping highest voltages off the movable
contacts. That means you need a form X or double-make
double-break configuration.
73 Tom
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