This has been a timely thread. As reported previously, I have a 40M 4-square
with 240 radials and recently installed a 2-el 40-2CD 40M beam at 50 feet on
an AB-577 portable military tower. Testing over a period of weeks revealed
that the 40-2CD is 1-2 S-units, or about 6-12 dB, louder than the 4-square
on most paths. I had expected the 4-square to do better on long-haul DX to
VK/ZL, but that was not the case.
Last week, I installed the 75' extension kit on the AB-577. Preliminary
tests show that the 40-2CD is now 2-4 S-units, or about 10-15 dB, louder
than the 4-square to EU from here in W1. I was a little surprised that the
difference was so pronounced, although EZNEC modeling shows that that the
extra 25 feet lowers the peak elevation angle by ten degrees, from about 35
degrees to about 25 degrees. I haven't tested the new setup on long-haul
paths.
I suppose my 4-square might not be optimum: it's on a hill so the feedpoints
are not exactly at the same elevation. It's possible that there's been some
degradation in the radial screen over time. However, F/B is still 20-25 dB
and dumped power is less than 2% at resonance. It's a great antenna,
especially for changing directions fast, but I doubt there's a contester out
there who would use it over the 40-2CD at my QTH, especially to EU. The
difference is just too big. However, I'm not going to take down the 4-square
anytime soon. But it's not to be able to switch from NE to SW quickly: the
40-2CD's F/B is so bad that it's not necessary! It's to quickly switch to
side angles or to quickly eliminate stateside QRM from strong adjacent
stations.
As someone said, more antennas is better!
If you can swing the 40-2CD at 1/2 wl or higher, go for it. Otherwise, the
4-square is still a great antenna. BTW, a 4-square with a full compliment of
ground-mounted radials requires a *lot* more work than a 75' tower. It took
most of one winter to build the elements, pre-cut the radial wires and
solder them to copper rings. It took another month or two to install the
elements, lay out the elements, and solder/weatherproof all the junctions in
the center of the square. It's less expensive than a new guyed tower with a
2-el shorty forty, but not exactly cheap: between the high-quality extruded
aluminum sections for the elements, mounting posts, phasing box, phasing
lines, baluns, coax, connectors, KW dummy load, dumped power meter, control
cable, various hardware and 7000 feet of #16 bare copper wire, I probably
spent over $1000. It can be done cheaper if you have a source for cheaper
aluminum/wire, already have the coax, build your own phasing box, etc.
It took about four hours to install the (used) 40-2CD on the (used) AB-577,
and maybe another four hours to take it down and raise it to 75'. I haven't
paid for the beam or extension kit, but the total would be less than $1,000.
73, Dick WC1M
> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]On Behalf Of Wes Cosand
> Sent: Friday, October 11, 2002 9:00 PM
> To: towertalk@contesting.com
> Subject: [Towertalk] 40M 4 Sq vs. 2 el Yagi at 70 ft
>
>
> K7LXC's recent comment about yagis vs. 4 square arrays got me
> thinking. Has someone done a careful comparison of these two
> antennas for
> 40 meters?
>
> I have relocated and have to build a new station and I am torn between
> these two alternatives. Although performance is important, the station
> will not necessarily be used for contesting. The initial cost is not as
> important as reliability and freedom from maintenance.
>
> I have previously had a 40M 4 square that was carefully installed
> with the
> DX Engineering phasing network. I was never tremendously impressed with
> the performance but I never had the opportunity to compare it to a
> yagi. And it certainly didn't require much care and feeding-- it
> just worked.
>
> I had decided to replace the vertical array at the new station with a 2
> element yagi at 70 or 80 feet, perhaps 12 feet above my five band
> beam. But the 40M yagi means that the total installation will be much
> higher than the 50 or 60 feet tower I could get by with if 20
> meters was my
> lowest freq antenna. The tower and rotor must be significantly
> beefier, and I am concerned that it will add to the maintenance
> needs. (The tower must be self supporting.)
>
> So why did ON4UN's 1998 survey indicate that among the top 100 DXers who
> responded about 40M antennas, 35% of them used 2 el yagis and
> only 7% used
> phased verticals? ON4UN said his survey indicated that at that time
> Cushcraft and Hy-Gain 2 element yagis were "extremely popular on
> 40meters".
>
> Wes, WZ7I
>
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