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[TowerTalk] RF current in REF + DIR ..how much ?

To: towertalk <towertalk@contesting.com>
Subject: [TowerTalk] RF current in REF + DIR ..how much ?
From: Dennis OConnor <ad4hk2004@yahoo.com>
Date: Wed, 22 Dec 2010 07:20:57 -0800 (PST)
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Jim, I would opt for the clamp on RF transformer...

Now, having said that, I recognize that anything we do to measure the RF 
current is going to upset balance, impedance, etc. to a greater or lesser 
degree..
I suspect the old RF meter ( I have a couple) is going to introduce enough 
resistance in the element to upset the coupling between the elements...  These 
were originally intended to be used on open wire line at several hundred ohms 
of Z...

With the clamp on RF transformer you can calibrate your RF voltage relative 
reading by using a signal source and either RF voltmeter or oscilloscope, or 
both, to give you voltage readings that can be mapped out as amperes...

But the issue is what do you expect to learn?  I don't see the ratio of 
voltage/currents without being able to measure vector/phase as being 
informative...  An example...

Two loaded short elements coupled to form a Yagi/Uda beam will have higher 
currents in both elements than a full size, unloaded Y/U beam for a given 
identical drive power...

A Y/U beam made of a folded dipole (300 ohm twinlead) driven element (or quagi) 
and a shortened, loaded reflector will have significantly different circulating 
voltage/currents between the DE/REF, yet still form a beam pattern...

This is a fascinating question that I don't have many answers for...  Maybe 
some of the gurus with electronic engineering background will discuss this...  
I await with great interest...

denny / k8do


      
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