Topband: Adding a Ground to Elevated Feed Vertical?

[Herb Schoenbohm]

On 11/29/2011 5:08 PM, Mark Adams wrote:
> I've been running my vertical for a couple of weeks now and it plays very
> nicely. The setup is:
>
> 85' up and 42' horizontal.
> Comtek 1:1 balun at feedpoint 7' off ground.
> 3 x ~137' radials all between 7 and 13 feet (driveway crossing height) off
> the ground.
> Fed with good coax.
> VSWR at rig end of coax is 1.9:1 at 1830 kHz.
>
> The question is whether it is worthwhile to install a ground rod under the
> feedpoint and connect the neg side of the balun to the ground rod (or maybe
> the shell of the 259 at the bottom of the balun). I'm asking because with
> my luck I won't be able to remove the rod once it is in and I cannot
> convert this antenna to ground radials because it is close to my driveway.
> OK, I could rent/borrow a horizontal boring rig.....
>
> 73,
> Mark K2QO
> K2 #543
> FN03ra**
> _______________________________________________
>
Mark,  An earth ground at the point you mentioned is valuable, not so 
much because of any change of the feed point impedance as a result, but 
since this ground can provide provides a protection against lightning.
The way you have described it a lightning bolt or  strike would need to 
travel back to you shack and rig to find a path to ground.   Having an 
earth ground at the feed point and a proper choke for draining of static 
build p on the inverted L is well worth the effort.  If you find the 
impedance change is gong the wrong way you could place the requisite 
windings between the coax  and the earth ground to isolate the RF ground 
from the electrical ground and still have the value of the protection.  
I am sure most would agree the actual change in radiation resistance all 
depends on the ground type and conductivity.


Herb Schoenbohm, KV4FZ