> This is an interesting question.
> What is the advantage of a 4 square over a 3 vertical array. I
> have a 3 vertical array on 40 and it is switchable in 6 different
> directions. Directivity seems to be very good. What would be
> the advantage of going to a 4 square over a 3 antenna array?
Probably not much, if the three vertical array is done correctly.
Traditional 4 squares with 90/180 degree phasing are off a tiny bit
in phase delay from optimum, so they don't work quite as well as
they actually could.
That hurts gain about a dB, and F/B several dB.
If you compare a traditional 40-square (90/180 delay) to a three
element array with 1/8 wl spacing (two elements active) using
proper phasing ~135 or 140 degree phasing), the four-square has
less F/B ratio and about 1.2 dB more gain.
Eznec shows 5.33dBi gain for the four-square and 25dB F/B, and
4.01 dB with 30 dB F/B on a two active element antenna with 1/8th
wave spacing.
There obviously isn't a large difference.
I use 120/240 shift in my four square, which makes it about the
same F/B as the two element (~30 dB) but also gives about one
more dB gain over a regular phase-shift four-square (6.5dBi gain
using the same ground loss and frequency band as the other two
above).
Still a small difference, unless you are fighting for every last dB.
73, Tom W8JI
W8JI@contesting.com
List Sponsor: Are you thinking about installing a tower this summer? Call us
for information on our fabulous Trylon Titan self-supporting towers - up to
96-feet for less than $2000! at 888-833-3104 <A
HREF="http://www.ChampionRadio.com";>
www.ChampionRadio.com</A>
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|