[TowerTalk] More Radials = Higher SWR???

[Jim Brown]

On 2/5/2023 7:57 PM, Lux, Jim wrote:
> One of the nice things with the VNA is that you can do a calibration at 
> the end of the coax, so you don't have to figure out what the coax is 
> doing to the feedpoint impedance.  I mean, you also need to measure at 
> the source end of the coax, because that's what keeps the amplifier 
> happy, but when trying to figure out what's going on, the VNA provides a 
> lot more information.

DG8SAQ's software for the VNWA he designed 10-15 years ago includes the 
capability to subtract out a feedline whose electrical length is known. 
I've often used AE6TY to subtract out the length of a feedline without 
knowing its exact length, simply be exporting the data to SimSmith, 
adding a negative length of line, making an educated guess as to its 
length, and tweaking the length until I see the resonance.

You've got to do this anyway, even having good TDR data, given that VF 
varies with frequency.

73, Jim K9YC