[TowerTalk] Ferrite Balun on a LPDA?

[Mark Beckwith]

Tom, how would you recommend feeding/decoupling the feedline on a Tennadyne 
LP?

Mark, N5OT


> Arne,
>
> The Tennadyne log has two hot booms. Each boom is used as a
> conductor in a balanced transmission line. The elements are
> attached to those transmission line conductors which also
> serve as a boom.
>
> Many people install the antenna by placing a balun out at
> the end of the booms. This divorces the boom to coax shield
> path.
>
> Then they run the same coax they decoupled right along the
> boom, often taping it right to the lower boom.
>
> Now they have the coax shield they painstakingly decoupled
> from the boom being tightly coupled to a hot boom! The
> mutual coupling is so high it undoes what the balun did, and
> they are back to square one with terrible common mode on the
> coax. It's just about as bad as using a balun at the
> feedpoint of a dipole and then taping the coax to one leg of
> the dipole for 15 feet after the balun.
>
> None of this applies to any other system, unless that system
> has a "hot boom".
>
> 73 Tom