[Antennas] WxAU Balun

[Barry Sherwood]

Some of those reviews are scary! But, they do have a flashy website.

On Sun, Jan 2, 2011 at 9:21 AM, Terry Conboy <n6ry at arrl.net> wrote:

> On 2011-01-01 7:20 PM, Ron Youvan wrote:
> > John Hensley wrote:
> >> I recently took down a trap dipole which had been up for a couple of
> decades.  Cleaning up the balun which is also serving as a "T" shaped center
> support, I realized I had no idea how to check it.
> >> I would enjoy hearing from anyone who has messed with these things.  I
> have no idea what is inside.  The caps are black, the body is gray PVC about
> 1.5" diameter.  Grounding strap runs down the side.  I used to see these at
> every hamfest I went to.
> >> Before I forget the performance was lousy but then again, I winged it.
> >     A piece of coax (min-8 = 8X) or RG-141 or some such with 20 or 30
> ferrite beads around it between
> > caps, the inner goes to one eye bolt, the shield goes to the other.  They
> (usually) can only be hurt
> > with super QRO or corrosion.  The 1:1 balun is used to reduce feedline
> radiation (making your signal
> > just horizontal instead of H + V) and reduce the effects of a nearby
> conductive object unbalancing
> > your dipole so much.  I have never heard of them hurting a station.  I
> use one on my 40 meter dipole.
>
> What Ron describes is a W2DU balun, which is a "current" balun.  It has
> a longer body than the somewhat similar W2AU balun, which is a "voltage"
> balun, which probably has a trifilar winding on a ferrite rod inside.
> The W2AU balun come in both 1:1 and 4:1 variations, which look the same
> on the outside (other than labels).  These are all made by
> http://www.unadilla.com/
>
> With an ohm-meter, the W2DU will appear open-circuit between the antenna
> terminals.  The W2AU models will look like a short.  You need to test
> with a dummy load (200 ohms for the 4:1 model, of course) and measure
> the SWR or impedance at the coax input to see it it's OK.  It's a lot
> harder to test to see if it is actually providing proper balance and/or
> isolation.
>
> In general, a good current baluns are normally preferred, but make sure
> you check out the comments by Walt Maxwell, W2DU, at
> http://www.eham.net/reviews/detail/2300 .
>
> 73, Terry N6RY
>
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-- 
*Barry Sherwood
KF5GC*