[NLRS] [BC'ers] Fwd: Re: Anybody have experience with multi-band feeds?

[Marciniak, Ed]

What's the limit as spacing tends to zero on a dipole with a reflector (or ground plane)? With one director and one reflector, what is the limit?

What is the gain of a patch antenna less than the thickness of an aluminum rod?

6db at zero length isn't that irrational, though a bit optimistic?


----- Original Message -----
From: tom ring [mailto:taring at taring.org]
Sent: Sunday, March 20, 2011 08:22 PM
To: nlrs at mailman.qth.net <nlrs at mailman.qth.net>
Subject: Re: [NLRS] [BC'ers] Fwd: Re: Anybody have experience with	multi-band feeds?



On 15 Mar 2011 at 18:18, Dr. Gerald N. Johnson wrote:

> 
> At 1296, N6CA says 6' of boom gets 18 dBi and 12' of boom gets 20.5 dBi.
> 

>From my studies of buildable high gain V/UHF yagis and the equation I derived, 
this seems about right.  I used over 100 yagis and a significant percentage 
were K1FO.  Gain of long yagis (>1WL) expressed as a multiplier is linearly 
related to boom length.  Interestingly it intercepts 0 length at very nearly 
6dB.  I've always wondered about that.

So double the length can give you at best 3dB if the yagi is very long and the 
design is perfect.  +2.5 for double the length isn't bad if correct.

tom
K0TAR

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