[Antennas] question about a 6BTV

[Terry Conboy]

Hi Ken,

With ground mounting, the length of the radials isn't critical, since 
they only function to lower the resistance to currents flowing along the 
surface of the ground back to the common point at the base of the 
vertical and are non-resonant.  For a fairly good ground system, use 12 
radials that are 1/8 wavelength long on the lowest band.  Doubling the 
number of radials to 24 and lengthening to about 3/16 wavelength can 
raise the gain by about a dB.  Going to 48 radials each 1/4 wavelength 
gives you another dB.  Beyond that, you get diminishing improvements.  A 
nice reference is on the SteppIR website (start on page 16 of the pdf).  
As they explain, if you have only a few radials, they can be just as 
effective with shorter radials.  Their document also covers elevated 
radials (which do need to be resonant).
http://steppir.com/files/biggir%20instruction%20manual%2024%20pages.pdf

It isn't necessary for all the on-ground radials to be the same length.  
Just run them out as far as you can.  The shorter radials will increase 
the overall losses somewhat, but will still work fine (and there is 
evidence that the pattern will still be essentially omni).  Don't bother 
bending radials around walls, etc, since the RF currents want to flow 
pretty much in a straight line to/from the base of the antenna.  A small 
diversion around tree trunks or small obstacles is OK.

Yes, you can use wire mesh, but installing wires is a lot easier in most 
cases, and a lot of wire mesh is made from steel and will rust away in a 
few years in most soil types.  Insulated or bare copper wires work 
equally well.  Smaller gauge wires are OK, as long as they aren't 
physically fragile, since the current is spread among all the wires.

73, Terry N6RY

On 2010-11-14 7:16 PM, Ken Snipes wrote:
> I was given a used , but it real good shape, a 6BTV, and I'm thinking
> of ground mounting it, but was a bit curious as to the radial system
> to use... should I run as many separate wires , or perhaps a full
> circle of  wire mesh , or a big metal circle under the vertical?
>
> What would YOU do in this situation?
>
> KD4IEN
> 10-10# 74734