Topband: Balun Question

[Charlie Cunningham]

Hi, Gary

Should do fine!  The W2DU balun is a good current-mode design by someone who
knew what he was doing! 

As for 160, I do have a W2DU current mode balun, from Unadilla that is
longer that the 80-10m version (more beads) but I never really pushed it. I
did use it some n 80m. Actually on 160, I didn't really have need for a
balun with the inverted L antennas that I used. I expect that the
application for a 160 m balun is most likely for guy s with high dipoles and
inverted Vees, and really big delta loops. The w2DU balun will workat least
as well as, and probably better than, the W2AU balun that it woud be
replacing!

 Hope your dad enjoys it for many more years!  :-)

73,
Charlie, K4OTV



-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Gary
Smith
Sent: Sunday, October 27, 2013 7:45 PM
To: Topband at contesting.com
Subject: Re: Topband: Balun Question

Fellows,

Thanks for the on & off list replies, I just got back from a weekend 
away & read through them all. Part of me wants to just leave it as is 
but that's not practical, a good icing and the connections I made 
will fail. Since I need something to relieve stress from the 
copperweld and the weight of the coax, the W2DU 1:1 looks like it 
ought to cover the issues.

There's no telling when bad weather will hit and once there'ssnow on 
the roof I'm not going up to work on anything so I need to do it now. 
He only operates on 80M phone using a Viewstar PT-2500A amp so the 
W2DU 1:1 ought to be fine. Someday when I'm the one using the station 
I'll want to use it on 160 and I'm not sure how well that balun will 
do on 160 but that's for another time.

Thank you all for the thoughts and helpful suggestions.

73,

Gary
KA1J

> Unfortunately, optimum balun impedance and design really depends
> heavily on 
> the application,. There is no magic design that works best for all
> applications, and the issue is so complex that almost any article
> falls 
> short.
> 
> For example, the 5000 ohms pure R will not work at 1500 watts with
> all 
> antennas. With a balanced feeder having a balun termination
> impedance of 
> 2000 ohms, a balun would have 1732V RMS between conductors, and 866
> volts to 
> ground. CM voltage would be 866 across a perfect balun if the feeder
> were 
> perfectly balanced.  The 5000 ohm CM impedance balun would dissipate
> 150 
> watts in the cores, far beyond what any reasonable core stack would
> tolerate. The fact the antenna comes out of balance reduces the heat
> somewhat, but this clearly is a case where we WANT a reactive
> isolation 
> impedance to reduce heat.
> 
> Making things worse, a half wave antenna fed through 1/4 wave of
> open wire 
> might have an impedance of 6000 ohms or more. The above example was
> for 2000 
> ohms!
> 
> Without much effort, we can see why simplistic "always do this"
> rules just 
> don't work in the real world.
> 
> Every situation has to be case-by-case.
> 
> 73 Tom
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "Tom Boucher" <tom at telemetry.demon.co.uk>
> To: "160 reflector" <topband at contesting.com>
> Sent: Friday, October 25, 2013 10:49 AM
> Subject: Topband: Balun Question
> 
> 
> > Gary KA1J - take a look at this excellent article on ferriste
> baluns by 
> > GM3SEK:
> >
> > http://www.ifwtech.co.uk/g3sek/in-prac/inpr1005_ext_v2.pdf
> >
> > 73
> > Tom G3OLB
> > _________________
> > Topband Reflector
> >
> >
> > -----
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> 10/20/13
> > 
> 
> _________________
> Topband Reflector
> 



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