In the broadcast industry, AM towers have "isocouplers" made by
Kintronic among others, when they have other service antennas on the
radiator. As you alluded to, the idea is to not allow the feedline
surfaces grounded to the tower, to detune it by adding to its RF
length. If it were me, I'd probably hang an insulated wire off the
side of the tower and drive that on 136 kc or hang three, one on each
leg to try to get the wider tower effect and bandwidth, keeping the
tower cold. You could go the ferrite route at the bottom of the tower
to make the feedlines the same length as the tower, but I don't know
how well that would work, plus if it were me, I'd hate to splice into
those nice heliax lines. Either way has drawbacks. The skirt feed
solution involves climbing and clamping on homebrew insulated
standoffs holding wire.
73
Rob
K5UJ
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|