Topband: Balun Question

Sun Oct 27 21:11:25 EDT 2013

Hi, Gary,

That does sound like a nice location! Well, I worked over 300 countries with
antennas supported by trees, before I finally got a little 40' tower to
support my home-brew 5-band quad. In trees, I had 40 and 30m vertical
dipoles, 40m vertical yagis - some reversible,  -full-size 80m GP, and
inverted Ls for 160. I worked some good DXpedition stuff like 3Y0 etc.
through ferocious pile-ups - sometimes on "first call"! So towers are not a
necessity! For a friend, who lived in Virginia, I went out into his woods
and built a 5-element steerable 80/75m GP array that was a wonderful
"kick-ass" antenna for long-haul 80/75m DX!

So, I would think that you and your dad are pretty well set!  Have fun!!

73,
Charlie, K4OTV
.

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Gary
Smith
Sent: Sunday, October 27, 2013 8:51 PM
To: Topband at contesting.com
Subject: Re: Topband: Balun Question

Hi Charlie,

the mast for his inv-V snapped during Hurricane Sandy and I attached 
the apex to the highest remaining part of the PVC mast that snapped, 
that I can reach up to. So for this moment, his Inv-V is more of a 
dipole with the apex 10-15 foot higher than the terminations. Next 
summer I'll wrangle the original assembly up for him and the apex 
will be another 30' higher than it is now.

I had to fell a few trees that were interfering with the wires and 
now he has a clear space with no more interference. So no high 
conditions here, my INV-L is based 20' lower than the basement 350' 
away and is at the edge of a salt marsh with the wire over the tree 
tops. The highest part of my vertical run is maybe 20' higher than 
the apex of his V is today. No possible way to put up anything taller 
for either of us, no towers allowed. It's still a nice location 
though on the end of Long Island sound.

73,

Gary
KA1J

> 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
> > >
> > >
> > > -----
> > > No virus found in this message.
> > > Checked by AVG - www.avg.com
> > > Version: 2014.0.4158 / Virus Database: 3614/6767 - Release
> Date:
> > 10/20/13
> > > 
> > 
> > _________________
> > Topband Reflector
> > 
> 
> 
> 
> _________________
> Topband Reflector
> 
> 

_________________
Topband Reflector