On Fri, 2008-08-15 at 19:46 -0400, Gary Hoffman wrote:
> If you improve your grounding system, you will always be happy that you did.
>
> To say it will or will not reduce noise requires knowing a lot more about
> the specific details of your setup.
The grounding system for a vertical antenna is often deficient. That's
easily seen when the antenna SWR is low, but there's no matching
network. The perfectly grounded vertical should have a feed point about
35 ohms. If the number of radials and ground rods is small, they can
contribute resistance to the feed point impedance raising it towards 50
ohms for a better apparent match. But with the radiation resistance 35
ohms and the ground resistance contributing half that much, the antenna
efficiency is 2/3 what it ought to be for both radiation and reception.
So improving the vertical antenna grounding (more radials, 50 is a
start, 256 is considered enough in broadcast circles, and more rods)
hurts the match but improves the antenna efficiency. That may actually
increase the noise heard, but it will increase DX signals by the same
amount so ought to be a wash. Unless a radial happens to contact a
ground from a noisy power pole.
>
> If there are grounding issues (and maybe there are not) and you fix them, it
> can certainly help.
>
The good noise reception on a vertical is why some 80 and 160 meter
DXers use a loop or Beverage for reception (directivity, not efficiency
is the goal) and the vertical only for transmission. Its hard to beat a
vertical for low angle (and thus best DX) radiation and reception, but
the propensity of a vertical to hear in all directions makes it hard
without going to an array of verticals to hear the weakest of signals
over the noise. Even atmospheric noise can be directional, so a
directional receiving antenna can be a benefit.
73, Jerry, K0CQ
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