Cebik's book "Cubical Quad Notes", Vol. 1 has an entire chapter titled
"Separately Feeding Multi-Band Quads" He goes into great detail about the
various feed systems, unused stubs shorted vs unshorted, and much more. The
effect on gain, f/b, and feed point impedance is covered. The book has 219
pages of great modeling data on Quad designs. A second volume covers
advanced Quad designs considering the effect of conductor diameter, 3 and 4
el designs, and OWA types. Obviously he has spent thousands of hours
developing the information in these books. I think these are still available
from www.antennex.com
73, Dan, N5AR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Jim Lux
Sent: Thursday, April 20, 2006 6:58 AM
To: Jim Rhodes; denis coolican; towertalk@contesting.com
Subject: Re: [TowerTalk] Lightning Bolt Quad
At 04:43 AM 4/20/2006, Jim Rhodes wrote:
>I asked the Lightning Bolt guy about that once and he got very
>defensive about his feed system. Said the tuning would be all off and
>he wouldn't be responsible. Others have said the opposite, that
>quarter wave lengths to a switch were needed. I am sure there are
>many opinions on this.
This is a question that could be answered by modeling it. (that is, what's
the sensitivity of the design to this change) There are some tricks to
accurately modeling quads (the corners), but I think that Cebik's web pages
cover it. You also need to choose segment lengths that line up nicely.
>At 12:02 AM 4/20/2006, denis coolican wrote:
> >This four element Lightning Bolt Quad covers 20, 17, 15, 12 and 10
> >meters. It is fed by a common balum. (one input PL259 and 5 output
> >pairs of conductors)
> >
> >Does anyone know what type of balum this is and what would be the
> >replacement for it?
> >
> >I imagine the driven elements for each band has an impedance of
> >about 80 to 100 ohms. The feed into the balum is 50 ohms.
> >
> >If a person provides a 2:1 balum for each feed, would the unused
> >balums be terminated in 50 ohms or left open?
> >
> >Any more thoughts on this antenna?
> >
> >Denis Ve6aq
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