Hello Dick,
I'm not surprised, although the 6 dB per S unit estimate may
be 'optimistic'. MOST receivers I've measured are 'generous'
below S9, sometimes being only 1 to 3 dB per S unit. This
can be easily checked with a calibrated signal generator OR
any signal source and a Step Attenuator.
A 402CD at 60 to 100 ft is a GREAT performer. Even if you
put one up, I would still keep the 4 square. As you noted,
it can be a QUIETER receiving antenna and offers INSTANT
direction change for those non-EU multipliers. Many users
report that their 4 squares are often as quiet on receive
as their Beverages.
You can never have 'too many' antennas :-)
Tom N4KG
On Mon, 8 Jul 2002 "Dick Green" <dick.green@valley.net> writes:
> And the winner is...
>
> I just had the rare opportunity to compare two very different 40m
> antennas
> "side-by-side" and thought the results would be of interest. I've
> had a 40m
> 4-square with 60 buried radials per element for about five years.
> Yesterday,
> I put a used 40-2CD at the top of a 50-foot AB-577/GRC portable
> guyed
> military surplus mast (HD-73 rotor) and compared the two antennas.
> There was
> no contest at all: even at 50ft, the 40-2CD is 1-2 S-units louder
> than the
> 4-square. Assuming my 1000MP meter is calibrated for 6dB per S-unit,
> that
> translates to 6-12dB. I'm sure getting the 40-2CD up higher would
> improve
> these results.
>
> I say the opportunity for such a comparison is rare because most
> people
> replace one antenna with another rather than keeping the old one and
> adding
> a new one. We often see claims like "this antenna is so much better
> than my
> old antenna", when the comparison is actually made from memory of
> what the
> old antenna was like. That's subjective at best. There's no
> substitute for
> being able to switch back and forth under a wide variety of
> conditions. It's
> also nice when the difference is definitive, as it was in my test.
>
> I've been wondering about the relative merits of the 4-square and
> beam for
> some time. A couple of years ago, someone at a YCCC meeting
> complained that
> his 40m 4-square just couldn't keep up with the 2-el beams (can't
> remember
> who it was.) I disputed the claim, feeling that my full-size
> 4-square with
> 60 radials per element was reasonable close in performance to a 2-el
> yagi.
> This assertion was partly based on having done reasonably well on
> 40m in
> contests, partly based on denial (building a 4-square is a lot of
> work!),
> but mostly based on having misunderstood the theoretical gain
> numbers for a
> 4-square. I thought that a 4-square had about 5.5dB gain over a
> dipole,
> roughly equivalent to a 40-2CD. In fact, the gain of a 4-square is
> only
> 5.5dB over a single vertical (monopole.) Near as I can figure it, a
> dipole
> over real ground is about 5.5dB louder than a monopole over average
> ground.
> That would make a 4-square about equivalent to a dipole. The 40-2CD
> would
> therefore be at least 5.5dB louder than the 4-square, and probably
> more if
> the 4-square efficiency isn't optimum. That explains the test
> results pretty
> well.
>
> Before you call me a doofus for making that mistake, go try to find
> the
> numbers in the ARRL Antenna Handbook or in ON4UN's Low Band DXing --
> the
> numbers are there but you have to do a lot of flipping around and
> converting
> of dBi to dBd, adjusting for ground, etc. A simple table comparing
> various
> antenna designs under "typical" conditions would be nice, wouldn't
> it?
>
> I got really interested in the comparison when I noticed that as my
> contest
> scores got better by improving other antennas, my 40m QSOs always
> lagged the
> competition. Eventually, it became clear that I was giving away too
> much on
> 40m and that I must have been wrong about the 4-square. Luckily, the
> used
> 40-2CD became available for a one-year loan just as I was pondering
> what to
> do (the same fellow loaned me an extension kit for the AB-577/GRC
> that can
> raise the height to 75 feet.)
>
> Of course, a 4-square has other advantages. If the radial system is
> good,
> the radiation angle should be lower. I'll have to check that out on
> some
> long-haul paths. More important, the F/B of the 4-square is much
> better than
> the 40-2CD. The 4-square has an F/B of at least 20dB, while the
> 40-2CD seems
> to be about 5dB-15dB (hard to measure, but it's clearly not very
> good.) This
> could be important when stateside QRM is bad. Also, the 4-square is
> significantly less noisy than the 40-2CD. Finally, the 4-square can
> switch
> directions instantly. Still, all in all, I'll take the extra forward
> gain! I
> should get a chance to check out the 40-2CD in action this weekend
> in IARU.
>
> I've always loved the "idea" of a 4-square (an antenna you can build
> with no
> concrete and no help), and it really is an excellent compromise
> antenna, but
> it just doesn't cut it for bands higher than 80m.
>
> 73, Dick WC1M
>
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