[TowerTalk] 40m 4square - factors relating to gain

[Tom Rauch]

> Since I'm planning an antenna installation I did some modeling of a
> Cushcraft D-40 (half a 402CD) at 60 feet over poor ground (Diel Const
> = 10, Cond = 2 ... sandy Florida soil) vs a four square with 60 on/in
> ground radials per element.  The loaded dipole was about 2 dB better
> (at the same take off angle) than the four square (and a full size
> dipole would have been even better). 
> 
> The difference is enough for me to decide the four square isn't worth
> the effort on 40.  One of the common loaded/shortened two element
> yagis looks the winner unless one is on an ocean beach.  

Assuming the model is reliable, that is true for transmitting. I tend 
to believe that would be true in many cases on 40 meters and 
above, but not on 80 meters and lower where it seems modelling 
programs I have tried over-estimate Fresnel zone losses (at least in 
every case I have tried).

For receiving at HF, it is only *directivity* that matters. The four 
square will likely be much better for receiving, and that alone may 
make it worth while!

It is common but very incorrect folklore that "gain helps" on 
receiving. You see that in magazine articles, like those that say a 
5dB gain antenna improves receive 5 dB. That is not true. 

Directivity is important thing...not gain. An antenna that is -20 dB 
gain can have 15 dB of directivity, and be better for receiving than a 
5dB gain antenna.
73, Tom W8JI
W8JI@contesting.com 

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