Bob, Lew McCoy discussed this issue in his review of the Lightning Bolt
quad in CQ some time back. W4RNL (LB Cebik) confirmed Lew's
observations by modeling common feed point multi-band quads and
presented his data and results in (I believe) the 7th volume of the
Antenna Compendium. The bottom line is that there is a severe
interaction between the 20 and 10M driven elements which results in a
severe deterioration of gain and F/B on 10M. The other bands were OK.
Personally, I prefer separate feeds and use an Ameritron switch to
select each of the five bands on my quad.
You ought to read Cebik's article and consult his website for other
reliable info on quad performance and construction.
73, Joe
Bob T. wrote:
>I'm ready to put a Lightning Bolt 2 element, 20/15/10m quad up at 80ft. I want
>to do this right the first time, and get the best reasonable performance from
>the antenna. Lightning Bolt supplies a 2:1 balun for a common feedpoint. The
>owner of the company sez this is the best way to feed the antenna for max
>performance, anyone who sez otherwise is wrong. But...he can't supply figures
>or pattern pics. Others favor the gamma match method, but still I haven't seen
>any concrete evidence that this is the best way. (believe me, I've scoured the
>web) Still others say a common feed point (feed line)is just no good; the only
>way to go is seperate feedlines for each band. Still no facts or figures to
>back up this claim. I am primarily concerned with maximum forward gain and a
>fairly good pattern. I won't quibble over .5-1.0 db or so. If it makes any
>difference, I am also interested in integrating a 3 element 6 meter quad on
>the same boom. (seperate feed) and/or mounting a loaded 40 met
e
> r dipole along the boom of the quad. So, who has the facts? Please, no
> educated guesses or second hand anectdotes. Thanks.
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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