Hold on there partner.
The Antenna Forum example was a C3 not a C31XR.
Two elements on 20m, 2 (I think) on 15 as well. The example was
supposed to be generic although I used a C3 model. It shows what
happens with a ANY short boomed yagi. If you go a little too wide you
get a lobe straight up. The example I used was the C3 model on 15m. It
demonstrated that 27 ft was the widest you want to go with this beam.
Remember short boom. The other example had a longer boomed yagi 4 ele
on 15m and with it you can go to wider spacing for better pattern.
Of course all this needs to be modeled at the heights your beams will
actually be.
There is nothing wrong with going with smaller spacing with the C3,
matter of fact it may be just what you need to do on a shorter tower to
get some stacking gain. The C3 modeled very well at 27 ft separation.
At 30 feet it's just a little too wide.
Don't confuse wide spacing with more gain....it is not as when you have
short booms.
HF is not VHF, and since our HF antennas "see" ground reflection, it
plays a very important part on what the main gain lobe will do.
This is a case where shorter is better.
On the subject of 45G being able to carry the a few tri-banders. Don't
any of you remember when I had 12, 4 ele monobanders on my rotating
tower? on 20,15,10, and a couple of 2 ele 40s. Plus a bunch of wires to
boot.
I was either very lucky or Rohn is very conservative with their
ratings. It stayed up and survived some big winds.
I do admit I sleep allot better with the second tower carrying some of
that load. HI.
Jay, WX0B
K7LXC@aol.com wrote:
>
> In a message dated 99-12-16 19:49:59 EST, k2av@contesting.com writes:
>
> > > Great idea but F12 says that 37 foot spacing is really the minimum;
> > >they'd prefer more for these longboom antennas.
> >
> > >Cheers, Steve K7LXC
> >
> > That's what I've heard they say. HOWEVER, if you model a pair of C31XR's in
> > EZNEC, to allow element interaction, rather than the abbreviated method
> used
> > in
> > TA... then...
> >
> > ONLY the 20 meter forward gain is better at 37 feet + , nothing else. The
> > rest
> > of the optimums fall near 30 feet. And at those stacking distances, one is
> > not
> > off 20 meter gain optimum all that much. I would love to see the
> > particulars on
> > how Tom came up with the 37 foot minimum.
>
> Good thought. Natan, W6XR, has some of the data that he may be willing
> to share.
>
> The 30 foot spacing (I think) is what WX0B came up with too. He gave a
> VERY interesting talk on spacing at Dayton this year. Maybe he can enlighten
> us.
>
> Cheers, Steve K7LXC
> Tower Tech
>
> --
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Jay Terleski
WX0B - Array Solutions
www.arraysolutions.com
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