[TZ] Elevated radials vs buried ones

[Milton Holladay jr.]

I believe that you may have "over-thought" this:

It must *not* be coupled to earth ground. That is why the radials are 
fairly far above the ground., and relatively  few, like four, is better 
than a whole bunch, as a whole bunch will have more coupling to the 
earth, if they're both at the same height above ground level.

  At his test site, WmC tried putting the radials at several different 
heights and lengths. The test frequency was 920kHz. ; input R, 11 Ohms. 
((IIRC) (Keep in mind that he got 2 or 3 of these sites on the air and  
licensed.)

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Think back to VHF and UHF two-way antennas of the type where there was a 
vertical whip radiator and four horizontal ones that constituted the 
"ground plane": a marconi antenna way up in tne air.........

Same idea........

M

On 5/18/2016 11:00 PM, Harold Hallikainen wrote:
> Interesting subject! The elevated "ground radials" seem like we're driving
> the center of a dipole turned vertical with one side "flared out." The
> relationship to "ground" is interesting. I always think of a horizontal
> dipole or inverted V or similar as having a drivepoint that is balanced
> with respect to ground. With the vertical with elevated radials, one side
> of the antenna is definitely closer to ground, but not necessarily at
> ground potential. As I recall from reading the Beverage article this
> morning (and I first met Charles when he worked for CCA and came to check
> a new FM installation), one of the elevated ground systems ran the coax
> through some ferrites. The ferrites provide common mode attenuation and
> not differential mode attenuation. That would let us ground the coax
> shield on one side of the ferrite and have it float on the other. I
> suspect the voltage on the radials at the base are perhaps 1/4 the voltage
> at the base of the tower with respect to ground. The radials probably
> reach ground potential part way down the radial, then start going up
> again. Just guessing here.
>
> On losses, it seems that having fewer radials would not necessarily
> increase loss but would perhaps just change the driving point impedance.
> We might think of a tower with one radial as an inverted V turned on its
> side. If one side is particularly close to ground, we may get losses due
> to that (current through a resistive material).
>
> Anyway, interesting stuff to think about.
>
> Harold
>

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