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Author Topic: Side by side Moxon antennas in my attic?  (Read 1688 times)

Posts: 571

« on: January 24, 2013, 04:56:31 PM »

So, I currently have a hy-gain a v620 vertical and while I've hit 180+ countries, there's a certain area of the world that just doesn't get loud enough.  That's the area almost perfectly north of me which includes China,indonesia, etc.  I can hear them just barely, some of the time and if they can hear me, I would never know.
So I need an antenna with some gain.  I can't put up anything more than the vertical outside, but I have an attic that is about 45 feet long and at least 12 feet wide that is accessible to  an antenna without causing a fire.  I already have a dipole in the attic and it performs reasonably but not as good as the vertical. There is no wiring or anything steel. Just wood and asphalt shingles. The attic runs almost perfectly east west, the exact direction puts thailand 0 degrees north of me.
So, I can easily put a moxon for 15m in my attic which I plan to do (but not at -27C!)  The question is, what would happen if I also put a 10m moxon beside the other one, in the same plane?Will it cause interference, reduce gain or f/b?
Even a 3db gain over the vertical, with the reduction in noise and unwanted signals may make a difference for those stations I want to get.  If you can't hear them, you can't work them.
Thanks for any insight


Posts: 17483

« Reply #1 on: January 24, 2013, 06:08:45 PM »

Polar paths are problematic at the best of times.

Yes, you can put two Moxon's side-by-side in the attic.  I'd allow a couple metres
of spacing between them at least, but the 10m wires won't be resonant on 15m,
and vice versa, so there shouldn't be a lot of interaction.  (10m and 20m is more

Another option would be a 44' doublet running the length of the attic, which
would be 2 x 5/8 wave on 10m and 2 x 1/2 wave on 15m, fed with twinlead
to a tuner.  Then you can add parasitic elements for each band, starting with
reflectors (the ends would go against the far walls, with a gap between the
inner ends of the 10m reflectors.  Depending on the width of the attic, you
could also add directors to make phased 3-element yagis on both bands,
with a single feedpoint.

I tried a quick model, and got 10dB F/B with just reflectors, but that can be
improved with a bit of experimentation.  Half power bandwidth is around 50 degrees.
As long as it doesn't make your bandwidth too narrow.
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