[BC] Dominator Antenna

[Craig Healy]

One thing I've thought about for a while is using a J-Pole type antenna for
medium wave non-directional stations.

For example, one of my clients is a 1340 1kw non-directional station.  It is
combined with an FM on a roughly 550 foot tower, which is about 3/4 wave at
that frequency.  Near the top they have a tunable decoupling skirt so the
antenna effective height is a half wave or less.  It requires an isocoupler
for the FM and the 950MHz STL.  A large copper tubing coil is used for the
lighting and a couple of other things.  Base impedence is around 125 ohms.

What if this same thing was built as a J-Pole?  Ground the base of the tower
and run a 1/4 wave six-wire skirt from there up, grounded at the bottom.
Then set the feed as a J-Pole is done, partway up from the bottom between
the skirt and tower.

One of my other clients uses a skirt feed which is open at the bottom and
fed from there.  That tower is around a 5/8 wave, so it's OK for that
frequency.  The 1340 tower is too tall for that station.

One other advantage is the J-Pole doesn't really need the same ground
system.  That can be very helpful when adapting to an existing FM
installation.

Thoughts?

Craig Healy
Providence, RI