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forestrunner,

if you have access to the first 16 or so inches of the coax coming down from the feedpoint, try putting about a foot or more of type 31 ferrite snap on chokes right at the feedpoint and see what that does to your VNA readings.

it's pretty much impossible to make a truly balanced antenna system on a vehicle, so there are always some common mode currents trying to come back down the shield.

putting the ferrite on the coax forces more of the signal out of the antenna and just might have an effect on the inductive component of your readings.
(i actually don't know if it will affect it or not, im just guessing)

however, putting a bunch of ferrite at the feedpoint of a mobile install is always a good idea.
LC

[QUOTE="loosecannon, post: 777061, member: 1368"] forestrunner, if you have access to the first 16 or so inches of the coax coming down from the feedpoint, try putting about a foot or more of type 31 ferrite snap on chokes right at the feedpoint and see what that does to your VNA readings. it's pretty much impossible to make a truly balanced antenna system on a vehicle, so there are always some common mode currents trying to come back down the shield. putting the ferrite on the coax forces more of the signal out of the antenna and just might have an effect on the inductive component of your readings. (i actually don't know if it will affect it or not, im just guessing) however, putting a bunch of ferrite at the feedpoint of a mobile install is always a good idea. LC [/QUOTE]

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