Topband: Adding a Ground to Elevated Feed Vertical?
zr at jeremy.mv.com
Tue Nov 29 14:15:11 PST 2011
----- Original Message -----
From: "Herb Schoenbohm" <herbs at vitelcom.net>
To: <topband at contesting.com>
Sent: Tuesday, November 29, 2011 4:44 PM
Subject: Re: Topband: Adding a Ground to Elevated Feed Vertical?
> 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)
>> 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
>> feedpoint and connect the neg side of the balun to the ground rod (or
>> 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
>> OK, I could rent/borrow a horizontal boring rig.....
>> Mark K2QO
>> K2 #543
> 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
You will likely get as many different replies as there are repliers on that
IMO the answer is still no. You do not want any earth ground under the main
current concentration. Place the ground and arrestor at the house entrance
and also isolate the coax at the feedpoint from outer shield currents with
plenty of ferrite beads over the coax. I dont know if the Comtek is a
current or voltage balun.
Placing a mesh under the antenna as suggested on here several times is a
good way to reduce ground losses. Do not connect the mesh to anything.
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