[TowerTalk] Impedance difference on 4080V from Cushcraft?

[Tom Rauch]

> I would say your problem is on 40 not 80.  To me, covering
almost the entire
> 40 meter band at the 2:1 points says you have considerable
losses involved.

Not to me Bob.

L/D ratio doubles for the same size tubing, and there is
less loading. I would expect a 40M vertical to be VERY wide
even when efficiency is very high.

BW is a very poor way to judge efficiency.

> should be on the order of 1/4:1 like you have on 80.  I
would try adding
> more radials and see if the VSWR on 40 gets "worse".

Another effect Bob is when the antenna has a trap, the
impedance terminating the top of the vertical is no longer
looking into an open circuit. The effect of that, even with
the best trap or decoupling system, is to increase the base
impedance on the "trapped" band (in this case 40 meters).

He might have some ground losses, but neither BW nor base
impedance sound out of line to me for the type of antenna he
has. Was the impedance and SWR  measured right at the
antenna connector, or through some length of transmission
line?

73 Tom