[TowerTalk] impedance measuring antennas

[John Lyles]

Exactly Bob. But I wouldn't want to be the one who has to run up the tower for short, back down to press 'SHORT DONE' and back up for open, down to press 'OPEN DONE'....you get the idea!

I remember (oops, dating myself) when the big antenna ranges (like Harris' in Hannibal, MO, for television broadcast) all had the old HP8754 "portables" strapped up on their rigs. Now you couldn't give one of those VNAs away. 


-----Original message-----
From: "W5LT" W5LT at verizon.net
Date: Fri,  6 Mar 2009 13:19:06 -0700
To: n8de at thepoint.net
Subject: RE: [TowerTalk] impedance measuring antennas

> Accurate measurement of the antenna from the shack depends on the
> instrument. With a VNA (Vector Network Analyzer) and the short, open,
> termination procedure it calibrates out the cable and refers the measured Z
> to the end of the coax.  The AIM-4170 and all lab grade VNAs can do that. 
> Bob, W5LT
> 
> -----Original Message-----
> From: n8de at thepoint.net [mailto:n8de at thepoint.net] 
> Sent: Friday, March 06, 2009 1:34 PM
> To: jtml at vla.com; John Lyles
> Cc: towertalk at contesting.com
> Subject: Re: [TowerTalk] impedance measuring antennas
> 
> Isn't it a bit difficult to haul all that up to the top of a tower to  
> make measurements?
> Measuring at the shack end of coax is NOT measuring the antenna.
> Don
> N8DE