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Re: DRSSTC RF Ground

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 11:59 AM 8/7/2005, you wrote: 
Original poster: robert heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>

Ground in a garage. Dry hard concreat is a poor ground, even a counterpois
mat is poor.

I disagree.
Most cured concrete slabs are not all that dry (it's moderately hygroscopic, so unless you happen to live in the New Mexico desert and don't water anything in your yard or exhale in the garage, it will pick up moisture).

A counterpoise, properly built (i.e. radius > height of TC and reasonable metal content) should work better than any sort of earth ground, just on loss resistance calculations alone.


 Just drill a 1/2 in hole in the floor and drive a ground stake
through the floor.

If you're going to drill in your concrete, better make sure that you don't have a modern Post Tension Slab, or you might get a real surprise.

Also bear in mind that if you have a vapor barrier between the concrete and the underlying soil (a typical building code requirement) that you're going to be puncturing that vapor barrier. Probably not a real problem but something to think about. (I personally find it hard to believe that the VB remains intact during the pouring and curing process, so it's more of a 99.9% VB)

 Make shure you pick a location where you will not trip
over the rod near a wall etc. If you don't nead the ground any more just
remove your wire connection and drive the rod flush with the floor. No
lasting problem.
     Robert   H
--

It's hard to imagine a single rod 8 ft long and 1/2" in diameter having a lower impedance than many square feet of concrete with rebar in it. If the ground is so dry that you worry about the concrete having too much restivity, so will the ground rod.

There's a reason why concrete encased grounding electrodes (aka the Ufer ground) are standard practice these days.