Topband: Re: ON4UN Antenna

[Tom Rauch]

From:           	"Roy Koeppe" <royanjoy@ncn.net>
To:             	"Top Band Reflector" <topband@contesting.com>
Subject:        	Topband: Re: ON4UN Antenna
Date sent:      	Sun, 17 Oct 1999 13:31:37 -0500

> 
> I'm taking liberty to forward this from being posted on Antennas
> Reflector.
> 
> "An interesting analysis by Dr Sevick in his book 'Building
> and using baluns and ununs' in appendix IV.  He analyzed
> the loss of powdered iron type 2 as a loading coil and
> shows that up to about 2.8Mhz, it has lower loss than a
> typical loading coil, and at about 1Mhz, it can't be beat.
> He claims that its use is justified on the 160 meter band.
>  Pat W0OPW"

Hi Roy,

I disagree with that statement, based on actual measurements of 
inductors (rather than "paper estimates" of Q). I've seen some 
pretty wild calculations of Q, sometimes as much as twenty times 
higher than real world results.

With one widely circulated software program, I can "paper-design" 
or "analyze" and find inductors with Q's of several-thousands. In the 
real world.
 
I've measured Q in hundreds or thousands of inductors over the 
past 20 years. I've never measured Q>800 in an air-core inductor 
and three hundred or so in a soft-iron toroid. 

It is highly unlikely manufacturers and designers of broadcast 
tuning systems overlooked something as simple as a performance 
improvement through use of iron core inductors.

There are, of course, limited exceptions to any general statement 
in a complex subject.
 
Since ground system loss is of much more concern to efficiency 
for 160 meter operators than coil Q (unless the coil is very poor), 
we are beating a dead horse. Considering the whipped horse dead, 
I'll drop the topic with one suggestion: 

Never enter a mobile shootout with a toroid-loading coil..and don't 
expect to find one as a pull-out from a BC station tuning unit.


73, Tom W8JI
w8ji@contesting.com



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