When stacking antennas, IDENTICAL is the operative word, for the antennas,
feedlines, and baluns. The time delay through the system will affect the stack
phasing. You should convert the lower antenna to have the identical balun as the
upper antenna, installed exactly the same way.
Bill, N3RR
AA4NC@aol.com wrote:
> Thanks for the reply Scott. I guess what I really need to know is which side
> of the driven element is the "hot side" (i.e. goes to the center conductor),
> and which is connected to the coax ground. If you looked at the balun with a
> DC ohm meter, you should see one side connected to the center of the SO239 and
> the other to the ground. If I make the top and bottom antennas so that the hot
> side of the coax connects to the same side of the driven element, the phasing
> should be correct I believe...
>
> This reminds me of some of the discussions that audio professionals have about
> XLR connectors and whether pin 2 or pin 3 should be "hot". I think wars have
> been fought over that subject. Basically, in ham radio or audio, the bottom
> line is that it doesn't matter which side is which as long as it is consistent
> on both ends (or antennas in my case!)
>
> In a message dated 11/1/98 11:02:14 PM GMT Standard Time,
> sales@advantagecomm.net writes:
>
> << The XM240 balun is simply 3 turns around 3 stacked toroids going one way,
> then 3 additional turns reversing direction and going the other way. Cable
> is no-name rg400/thermax style cable.
> Scott
> KA1CLX
>
>
> At 05:31 PM 11/1/98 EST, you wrote:
> >
> >I'm testing a 2/2 40m stack that uses a Cushcraft 402CD@70' and a
> XM240@130'.
> >I'm feeding this with a WX0B stackmatch. The 402CD is directly coax fed with
> >some ferrite beads over the coax , and the XM240 uses the Cushcraft MNXM
> >balun.
> >
> >I'm finding the 2 antennas seperately to be close (within 3-5 dB of each
> >other) as expected. What I find that bothers me is that the stack is almost
> >always slightly weaker than either of the antennas alone. I wonder if it is
> a
> >phasing problem?
> >If so, the bottom antenna would be easier to test phase as I can tell which
> >side of the driven element the center/ground of the coax are connected to. I
> >need to find out what the phasing is on the MNXM balun for the top antenna
> so
> >I can tell if the bottom is out-of-phase. Does anyone know how this balun is
> >wired?
> >
> >Any ideas/suggestions would be appreciated.
> >
> >73,
> >
> >Will
> > >>
>
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