The AM Forum

http://www.youtube.com/watch?v=0sLv4LLVPbA

Chuck

Good trick.

Another is to grind the point longer & sharper, will make it a lot easier to drive.

73DG

An amazing method which I learned from an experienced tower man years ago allows driving a 4 foot rod into regular soil without any hammers or impacting...

1.  Dig a 6 inch deep by 6 inch round hole where the rod is to go. 

2.  Fill with water.

3. Insert rod with hands several inches.

4. Work rod up & down, allowing water seepage into rod hole.

5. Refill with water as required, and continue working up & down.

6. When fully installed, connect cable & backfill as needed.

Note:  doesn't work well with rocks!

Chris

Chris,
the disagreement with your method is that is doesn't meet the requirement for 'full contact with undisturbed earth'.

If ya' can't do it with a sledge hammer, rent an electric hammer/drill with ground rod accessory.  The smart way.

That and 4' rods are not code out here.  Nobody even sells them here.

73DG

I have an 8' piece of 1/2 emt conduit with a water hose connection soldered to one end.  Place the conduit where the ground rod is to be placed and turn on the water.  The water will wash the conduit down into the ground.  When the proper depth is reached, remove the conduit and insert the ground rod into the hole.  Takes very little effort to sink an 8' ground rod if there is no rock.  That's another story.

I have 7 ground rods here.  A halo around the tower, Intermediates and outside the shack wall.  They where a pain in the A$$ to install.  I want one of those Bosch roto hammers.  At my old property a friend had one and put in 6 rods for me in about 15 minutes.

C

I guess I'm lucky, if I don't find a tree root or rock, the ground rods drop 4-6 inches with every wack.  My house is sitting on dry sand/clay under the top soil.  I don't know how good a ground connection I have, but at least I can add rods at any time.

Putting in some rock salt as used in water softener systems will improve conductivity. Drop a few handfuls down the pipe before connecting hydraulic apparatus, then let the pressurized water dissolve and distribute it as part of the job.

Not advised if you've got nearby trees you happen to like.

As far as I'm concerned, the common ground rods are just cosmetic - to please a code inspector. 

If I'm wanting a decent earth ground to provide a high current path for lightning currents, I bury 4 inch copper strap - either in a 1-2 foot trench around the building, or to be really effective, as three radials from the tower out to the guy anchors.  Maximum surface area against soil, and spreading the contact over a large area.

Chris

ftp://ehzftp.wr.usgs.gov/gjensen/MOTO-R56-STDS.pdf

The Motorola communications site grounding bible.  There is a lot of Motorola internal legalize, but when you look at the diagrams and specifications it's pretty straightforward and simple to understand.

The link probably won't work directly, it's an ftp.  Copy the address and enter it into your search machine, then click the result.

That link, when copied to your browser, won't work either. http should not precede an ftp link. With this type of link, you need to use bracketed url, /url stuff. Without it, when you post your message, it will automatically add http:// (as you can see from your post) which will take to an entirely different site.

ftp://ehzftp.wr.usgs.gov/gjensen/MOTO-R56-STDS.pdf (http://ftp://ehzftp.wr.usgs.gov/gjensen/MOTO-R56-STDS.pdf)
With the bracketed url, /url, no "http://" appears. Now, copy this entire link to your browser.

  i have a dug well, and the river...climbed down the well and connected up 4 8ft rods....river never freezes, wire down to it, with 2 8 footers in there...lucky...

..sk..

It would be interesting to measure the resistance of a ground rod driven in with a fence post driver and hammer vs. a rod inserted into a hole drilled by water pressure. The former method provides a much better connection to the earth.


So will Epsom Salts (magnesium sulfate), and it won't kill vegetation or corrode the rod.

Just to note that the buried radial wires of AM broadcast stations are plowed into the earth.  That process disturbs the earth, yet those buried wires perform as theory predicts.

Antenna radials are performing a completely different function than an electrical or lightning ground rod.

Radials are carrying RF current from the EM field back to the feed point.  They are not intended to couple with the soil.  They actually are replacing the soil for that purpose.

A safety ground rod is carrying DC or very low frequency AC from either the mains service or lightning.  It's function is to couple with the soil and where the current is dissipated.   The Motorola guide shows how halo's, grounding radials with either rods, bare wire or cement encased wire serve the same purpose.

Of course elevated radials perform well without contact with the soil..... Does that mean that ground rods would work great if we pointed them up?  Sure would be easier to install.   :)

Many people  are not aware of the difference between these two types of grounds.

(Yes, I understand you are a broadcast engineer).

The r-f current carried by buried radials enters them from the earth in which they are buried.  The currents flow first in the earth, and then are diffracted into the radial wires.

Also the a-c resistance of even a few buried radials is less than that of a ground rod (see NEC-4.2 analysis below).

How do explain successful antenna radial systems with insulate wire?

Alternating current couples through the insulation to reach the conductor.

There is no magic here. There are many ways to achieve a good ground, but always remember that the key ingredient in a low ground impedance is the amount of surface area in contact with earth / over a large area.  It is easy to do the math on various methods.

An AM radial system is designed to function as one half of the antenna capacitor, to collect currents.  But because it also has a large surface area spread over a wide area, unless installed in virtually non-conductive soil, makes a good lightning ground.