A half wave antenna is easiest fed in the center. A quarter wave is best end 
fed.
A quarter wave should have at least 3 radials a little longer than 1/4 wave. 
Unradiated power has no place to go except into heat. The transmission line 
between the transmitter and the antenna should be an odd multiple of 1/4 
wave to avoid unnecessary tuning problems.
BTW, coax cable is very lossy at UHF frequencies.

John Ferrell  W8CCW

"A nation of sheep will beget a government of wolves."
-Edward R. Murrow
----- Original Message ----- 
From: "Vitaliy" <piclist@maksimov.org>
To: "piclist" <PICLIST@mit.edu>
Sent: Tuesday, February 02, 2010 9:19 PM
Subject: [EE] Antenna efficiency


>A question for the antenna experts.
>
> I'd like to know what happens when you go from a half-wavelength to a
> quarter-wavelength antenna, while trying to maintain the same output power
> from the receiver's POV.
>
> In other words, let's say that to compensate for shorter antenna length, I
> swap out my 1W transmitter with a 2W one. Would that even work? And if it
> would, what happens to the extra power -- does it get converted to heat
> inside the antenna, or does poor SWR cause the energy to be lost inside 
> the
> output stage?
>
> If I sound like an idiot (which I suspect I do), I would appreciate it if
> you could point me to a reference that would help explain this.
>
> Best regards,
>
> Vitaliy
>
> -- 
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