From: WarmSpgs@aol.com
Message-ID: <1c.1583c8a.25f92b2e@aol.com>
Date: Thu, 9 Mar 2000 11:28:30 EST
Subject: Re: LF: Re: LF antennas
To: rsgb_lf_group@blacksheep.org
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

Oops!  Between the time I composed my message and the time I finally 
reconnected in order to send it, Mike and others had already commented on the 
2.6dB directivity.  However, I believe my observation offers a way out of 
having to consider ground losses twice.

If we refer to vertical pattern directivity and azimuthal pattern 
directivity, we understand them to be assumed ideal conditions.  Since the 
overall gain is the mathematical product of those two factors and the 
real-world losses, the losses can legitimately be lumped into one single 
factor of the product that affects the whole outcome.

Of course, that factor may be a complicated one to describe mathematically in 
the real world, involving in the simplest case the radiation resistance of 
the antenna versus losses in the tuning coil and earth; and in more 
complicated cases, involving the added problem of other objects in the 
vicinity, their conductivity, the mutual impedances between them and the 
antenna, and so on.

But I think the important point is, the loss factor can be legitimately 
separated from the two directivities, and thus allow us to consider them in 
the realm of the ideal.  It's just that, when comparing antennas, we need to 
specify whether we are talking about overall gain (which includes the loss 
factor) or directivity alone.

73,
John