Message-ID: <1999040509441968199@zetnet.co.uk>
Date: Mon, 5 Apr 1999 09:44:19 +0100
To: rsgb_lf_group@blacksheep.org
From: "Peter Dodd" <g3ldo@zetnet.co.uk>
Subject: LF: Re: CFA
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CFA Antenna
> I have obtained a copy of the patent spec for this invention. From a patent
> spec someone skilled in the art ought to be able to make a CFA without
> assistance from the inventor.

You might think so. I was recently engaged as an expert witness in a 
case of a patent infringment involving a radio circuit involving 
filters. The patent write up was, in the main, technical gibberish. 
Most of my efforts went into trying to make sense of it.

It rather dented my faith in the patent procedures 


> Having read the spec I have come to two conclusions:

> 1) I am not skilled in the art
> 2) the First Law of Engineering applies (any useful advance has at least one
> major disadvantage). In this case I wonder if, as we make the CFA a smaller and
> smaller fraction of a wavelength, it becomes more and more difficult to
> maintain the correct relative phasing and amplitude of the two feeds?

Try to get hold of the Wireless World article "CFA-RIP"

The best patent I have read is the one by James F Corum on his toroid 
antenna, which appears to have been written very skillfully. It 
covers almost every concevable configuration of the antenna but 
leaves out something essential, which in this case is the feedline 
impedance matching network. This means that you cannot easily 
reproduce it from the patent write-up. 



-- 
Regards, Peter, G3LDO

<g3ldo@zetnet.co.uk>