Someone said: (Sorry, I have lost the original E-mail item in MSIE)
snip
The lower the feed impedance, the greater the current in the driven element,
which results in increased gain. Below 10 Ohms, efficiency may become suspect,
but above 10 Ohms or so, the gain seems to be real and realizable. The time
honored solutions to this matching problem have been gamma or hairpin matches.
snip
I have been waiting for some other loud mouth know-it-all to respond to this
statment, but I guess I will blurt it out!
Parasitic elements near a driven element, lowers the feedpoint impedence of
the driven element, it also compresses the baloon and provides gain.
INCREASING the feedpoint impedence of a driven element (like it being a loop)
lowers the current (at the same power level, increasing the voltage) reduces
the IR losses, increasing the `efficency' , this gives the qubical quad a one
element advantage over a yaggi, but remember the yaggi is most likely alum. and
the quad is most likely copper which also helps efficency a bit. {if both were
made from a poor conductor like steel it would be more important!}
Just remember a 450 ohm feed line is more effecient then 52 ohm feed line
because of the lower current & higher voltage, it is what makes waveguide more
efficient than coax.
Belden made 50 ohm 1 kw twin lead when I was a kid.
Notice I have not mentioned radiation resistance, just effency from impedence!
de Ron ka4inm@gte.net Best Regards
VISIT my WEB SITE at: http://www.qsl.net/ka4inm/
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