On 6/1/16 7:10 AM, Jim Thomson wrote:
Date: Tue, 31 May 2016 17:37:52 -0700
From: Grant Saviers <grants2@pacbell.net>
To: Jeff DePolo <jd0@broadsci.com>, towertalk@contesting.com
Subject: Re: [TowerTalk] Change in Frequency As Antenna Height Rises
A little sloppy, I should have said "transforms to some other SWR on an
SWR bridge".
We agree there are a couple of much better measurement means. Your
"lacking that" example still requires a measuring device that can do TDR
and complex impedance measurements which a classic "SWR Bridge" can't do.
It still seems a bit bizarre to me to be tuning individual elements of a
beam near the ground with an SWR bridge. Also, several classic
"great/proven" beam designs have been redesigned with good modeling for
much better performance out of the same pile of aluminum. And some well
known brands showed zero gain in the K7LXC et al yagi tests raising big
questions about "manufacturer's data.". It's gonna be hard to convince
me that there is a better way than good modeling to design a beam.
I agree that I'd trust the model more than measurements, particulalry
close to the ground.
One might use previously measured data for "close to the ground" to
allow a person to verify that the thing was assembled properly.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|