[Antennas] Quad matching

Tue Aug 24 05:32:46 EDT 2004

> Hi folks,
> I've been using quads for over 40 years and I have always fed each band
separately.
> I am curious if any "quaders" have had any luck with just tieing all the
driven elements
> together and fed them that way.
> I know that it has been done, and I wonder if there is any data that
shows how much difference there is in this method in regard to performance?
> Not being a big gun, in fact operating QRP a lot, I can't stand a whole
lot of loss or ineffeciency...but, it it was a tolerable amout it would make
things much easier as
> I prepare to rebuild my antenna after moving back here to TX.
> Thanks in advance for any opinions.
> 73, Tom K5IID

 Hi Tom..
 Like yourself, I've been playing with Quads for 40
years, and I've always found seperate feeds much better.. 'specially on
Quads with more than 3 bands. A useful compromise is to use two feeds , with
20, 15 and 12m on one feed, and 17 and 10m on the other. This helps with the
two main interactions between 20 and 10m, and 12 and 10m. If you're direct
feeding with coax, choke baluns at the feed points are a must.
 LB Cebik has done a huge amount of research into this whole area, and
all the info is at www.cebik.com .
 Quads fed with a single feed usually get out well, so their gain seems
reasonably unimpaired, but the radiation patterns from 15m and up are
usually bad, with almost no side nulls. However, I would definitely NOT
write off a Quad just because it has only one feed, and I think that the
Lightning Bolt Quad is about the best "bang per buck" on the antenna market.
 Opting for seperate feeds is not neccessarily going to improve things
dramatically, unless it is done properly... Again, check out www.cebik.com
on this one. For best decoupling of unused elements, the feeds should be
switched 1/4 wavelength back from each feedpoint. This allows them to act as
shorting stubs on the unused elements, and so maximise their isolation from
the active elements.
 73
 John EI7BA http://www.iol.ie/~bravo/