Topband: VF - It is what it is

Richard (Rick) Karlquist richard at
Thu Mar 29 16:28:53 EST 2007

> My solution to the changes-VF-over-time problem in a crossfire phased 
> system is:  To first use equal lengths of it from each Beverage to 
> reach a common point ahead of the un-un. (Change of VF in these 
> sections will not matter, since both pieces are the same length of 
> the same cable, cut from the same spool.  Both pieces will remain the 
> same electrical length as their VF changes identically.)  Then, to 
> add the phasing line to the line from the rear staggered Beverage as 
> a separate piece of cable.  This way the section of line being used 
> to achieve the proper phasing angle of the two antennas can be 
> disconnected periodically, it's VF checked, and be replaced if need 
> be. This would also allow the null to be easily moved for any other 
> Charles - K5ZK

Or you could use a pi network as a lumped delay in place of the separate
piece of cable.  Then you don't have to worry about cable aging at

Rick N6RK

More information about the Topband mailing list