My friend had a 4-element 2m quad with dangerously high VSWR. Somebody gave
it to him (which I guess was the first sign). Yesterday, he brought it by
for me to check it out.

I don't have an analyzer (yet) for 2m, but careful VSWR measurements made it
look like the antenna was resonant out-of-band low. We carefully measured
the driven element length and compared it to the calculated length from the
ARRL Antenna Handbook. It was about 1.3 inches too long, so we stripped out
the spreaders, redrilled and reassembled with a shorter driven element.
Voila! 2.1:1 to 2.4:1 across the bad, with the low point in-band. He went
on his way, happy.

Last night I studied a little and saw that the quad loop is normally
resonant with about 100 ohms at the feedpoint. I used some # 12 wire to
build a 222 MHz quad loop today and, sure enough, 2.1:1 was the best I could
do. I remembered the use of a quarter wave section of line as a matching
transformer and decided a transformation of 50 -- 75 -- 100 was too easy
not to try. At 66% velocity factor, that's just over 23 cm of RG-59.

It worked perfectly. Resulting VSWR was better than 1.4:1 from 222 to 225.
From my location south of San Diego, I brought up several distant repeaters
(Hollywood Hills, Catalina) and even worked a guy in Santa Barbara through a
repeater at his end, over 200 miles away. All this with 5 watts to my
humble quad loop on a 9-foot plastic stick tied off to the patio cover.

I understand that a quad loop has a pattern about that of a dipole and a
quad array will deliver useful gain with just one parasitic element. Dunno
if the parasitic should best be a reflector or a director but I'll find out.
I built a reflector but haven't tested it yet in conjuction with the
exisiting loop. That's next.

I love this hobby!

"Sal"
(KD6VKW)