In a message dated 2/18/2010 11:12:25 P.M. Eastern Standard Time,
I'm certainly not trying to argue with you, Dick; perhaps I'm way off
base. I'm not an antenna expert. Why don't we see what the others on the
Topband list have to say about the radial requirements for a half wave
If I recall, I don't think that using a 1/2 wave vertical "gets around
having to mess with an extensive ground-radial system".
Mike and Dick,
I just ran some EZNEC models on a 132 foot vertical Vs. a 264 foot
vertical operating at 1.82 MHZ, and here is what it says:
Perfect Ground (same as lots of ground radials)
132 foot vertical : Max Gain = 5.15 dbi @ 0 Degrees
264 foot vertical : Max Gain = 6.76 dbi @ 0 Degrees
No Radials (just a ground rod) with Average Soil Conditions (0.005 S/m)
132 foot vertical : Max Gain = -3.59 dbi @ 22 Degrees
264 foot vertical : Max Gain = 1.25 dbi @ 16 Degrees
No Radials (just a ground rod) with Poor Soil Conditions (0.001 S/m)
132 foot vertical : Max Gain = -6.93 dbi @ 27 Degrees
264 foot vertical : Max Gain = 0.05 dbi @ 19 Degrees
I'm using the demo version of EZNEC, so can't do analysis using actual
ground radials, nevertheless the above analysis is indeed interesting. It
shows that the 1/4 wave vertical does indeed suffer more loss in gain as well
as a higher angle of radiation compared with a 1/2 wavelength vertical under
identical soil conditions.
On the other hand if your trying to create a perfect ground condition via
the use of ground radials, then I would guess that the 1/4 wavelength
vertical would offer almost identical performance as the 1/2 wavelength
without the need of such long ground radials but this is just based on my
intuition (no data or model in hand to support this). My above numbers also
do not reflect any matching network losses, etc.
Hope this makes sense, and lets see what others have to say.
UR RST IS ... ... ..9 QSB QSB - hw? BK