Topband: K3NA Loop Array

[Milt, N5IA]

Greg,

If I understand your comment and question correctly, my answer is the 
following.  These are my opinions based on the knowledge I have obtained and 
the experience of working with Beverages for 15 years.

You are correct that the pattern of a Beverage over good ground would be 
nearly the same as the pattern of a Beverage over poor ground.

You are correct that the unwanted atmospheric noise is lower in direct 
proportion to the level of the desired signals.

If the ground referred to in your comment "that the ground is not so good" 
actually refers to the grounding provided for the termination resistor at 
the far end and the grounding provided for the matching transformers at the 
near end, then you are incorrect.  The grounds really have very little to do 
with the gain and/or SNR of the antenna itself.  Their purpose is to aid in 
the proper matching at the near end for signal extraction and the swamping 
of the reverse signal at the far end, thus rendering the design 
uni-directional.

If the ground directly underneath the Beverage wire has high conductivity, 
the effect is less signal voltage impressed into the wire.  This can be 
compensated for by making the Beverage longer so that more signal is 
accumulated at the near end.  The practical number of wavelengths for a 
Beverage over high conductivity ground to achieve useable signal level and 
at the same time not narrow the main lobe too much is probably about 8.

With poor ground and a low velocity factor of ground 1/2 of the 
"transmission line" there is a practical limit of about 4-5 wavelengths that 
the Beverage can be extended before the signal delay in the ground side 
reaches 90 degrees lagging the signal induced into the wire.  After that, 
any lengthening of the Beverage actually decreases the signal level although 
the pattern will continue to become more narrow.

Perhaps this explanation will help understand the relationship of "good" 
ground vs. "poor" ground underneath a Beverage and how it affects achieved 
signal levels into the RX coaxial cable.

de Milt, N5IA

----- Original Message ----- 
From: "Greg - ZL3IX" <zl3ix at inet.net.nz>
To: <topband at contesting.com>
Sent: Thursday, June 24, 2010 1:06 AM
Subject: Re: Topband: K3NA Loop Array


> Thanks for all the comments on this.
>
> Reading between the lines, I think I can assume the following.  A
> Beverage over good ground will still work as well as over poor ground,
> *PROVIDED* that the ground is not so good, and the wanted signal levels
> therefore so low, that they are not able to override the receiver
> noise.  The pattern and RDF and the same whatever the type of ground,
> and the unwanted atmospheric noise is lower by the same amount as the
> wanted signal.  Correct?
>
> 73, Greg ZL3IX
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK