[Elecraft] OT: Vertical antenna ground systems

[Don Wilhelm]

Alan,

LB Cebik and UN4UN (Low Band DXing) had some information on using tuned 
radials - this is a situation that is covered under the topic of 'raised 
radials'.  The tuning technique is to tune each radial with the vertical 
monopole separately - tune for reactance (X) = zero which is the 
resonant condition  without respect to the actual SWR or resistance 
part.  Tune each radial in  turn (one at a time), and when all have been 
tuned, connect them all together to form the 'ground plane'.  After that 
resonance tuning is complete, one can design a matching network to match 
the resistive portion of the feedpoint to the feedline characteristic 
impedance for best power transfer.

The conditions found by someone else in his particular situation may or 
may not be applicable to the situation that your antenna exists in.

73,
Don W3FPR

Alan Bloom wrote:
> N6LF has done some wonderful experimental work on vertical antennas.
>
> He found that a radial laid on the ground experiences a velocity factor
> similar to coax cable.  A quarter wavelength is only about 60% of its
> free space value.  If you make the radials a physical quarter wavelength
> long, they are actually closer to a half-wave electrical length
> (anti-resonant).
>
> With 4 radials he actually got about a 3 dB improvement by making them
> SHORTER!
>
> For my next vertical I will definitely plan to tune the radials.  I
> think I'll try laying out a 1/2-wave dipole on the ground and then trim
> it to resonance.  Then cut all the radials to equal the length of one
> half of the dipole.
>
> Al N1AL
>
>
> On Tue, 2008-11-04 at 19:10, Ken Kopp wrote:
>   
>> Of potential interest to those who use verticals with their Elecraft 
>> rigs.
>>
>>          http://www.antennasbyn6lf.com/
>>
>>
>> 73!  Ken Kopp - K0PP
>>       ElecraftCovers at rfwave.net 
>>
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