Here's a quick look using EZNEC models I had on hand,
all assuming EZNEC high-accuracy "Good" ground (0.005, 13):
dBi @ peak TOA
4-square (EZNEC's 4square.ez) 5.34 @ 25 deg
4-square (EZNEC's 4sqtl.ez) 5.29 @ 25 deg
Dipole @ .5 wl 7.63 @ 27 deg
2 el Yagi 16' boom @ .5 wl 11.56 @ 26 deg (+6.2 dB over 4SQ)
The 16' boom model happens to be the only 40M 2 element I had but it
should be a reasonable comparison to the 40-2CD (23' boom should give
higher gain but probably +0.5 dB loss due to loaded elements). The
above gains for the dipole and Yagi would drop at lower heights and I
would not personally not use them at less than .5 wavelengths.
The above is essentially what I posted previously so my
memory did not completely fail me:
"This should be no surprise. Even a dipole up 1/2 wavelength
will beat a 4-square. I recall a dipole's gain is in the order of 2-3
dB over a 4-square for equivalent grounds. Add another 4-5 dBd for a
2 element Yagi and you are around 6-8 dB over a 4-square. The only
place a 4-square can realistically compete with a Yagi is if you are
over salt water."
73, Bill W4ZV
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