[Boatanchors] Ground wire? Ho Ho!

Thu Mar 22 00:05:57 EDT 2012

Hello Phil,

The major omission in your tale is what you say of your antenna - absolutely 
nothing. So, your discussion of grounding is groundless.

You need to consider the purpose of your 'grounding':

Is it for lightning protection?
Is it for mains safety?
Is it part of a tuned antenna system?

The correct solution for each of these is different. What you have described 
is faintly appropriate for mains safety, but not lightning or RF purposes.
For RF purposes, there are several possible grounding systems - none of 
which bears any resemblance to what you have described. A tuned antenna 
system will always give the lowest noise - resonance means higher Q, means 
lower bandwidth, means less noise.

If you use a vertical 1/4-wavelength antenna, then your ground spike should 
be immediately at the base of your vertical. That ground spike should then 
be connected to the underlying Earth by as low resistance a method as 
possible. All resistance in your Earthing system is in series with your 
antenna, but as it cannot radiate, all it does is heat up the Earth, thereby 
reducing the efficiency of your antenna.
To avoid the variability of resistance to Earth, you could use a 
counterpoise system. In this case, the ground wires should be odd multiples 
of 1/4-wavelengths of the frequencies you want to use, but kept above the 
surface of the Earth, and in particular, not Earthed at the end away from 
your vertical. Then, you will have a safety issue - the far ends of the 
resonant counterpoises will be at high Voltage and so will need insulation 
and some means of keeping vulnerable beings away while you PTT.

If you use a G5RV or any form of balanced horizontal dipole, then no 
grounding or Earth spike is needed.

However, if you use an end-fed Zeppelin, then how you feed it determines any 
grounding / Earthing you will need.

With your system of Earthing the far end of your so-called ground leads at 
1/4-wavelengths, you force an otherwise high impedance point to be low 
impedance, and then your feedpoint becomes a high impedance junkyard, and 
the radiation pattern becomes a can of spilt spaghetti. Your antenna 
coupling unit becomes a water heating centre for your coffee.

Alternately, you could always imbibe from the ARRL Antenna Handbook. On the 
other hand, you could read any of the multitude of so-called expert books on 
the subject; the problem with this approach is that a great deal of what 
passes for expert comment is a load of armchair musings with little 
connection to physics or electronics. The ARRL Antenna Handbook does not 
suffer quite so much in this regard.

73 de Brian, VK2GCE.

On Thursday, March 22, 2012 11:36 AM, Phil said:

> Hi All,
> This is the summer of "fixing needed things up around the shack".  One
> of the things that's needed work for a number of years was the ground
> system (there is NO room around this mobile home for a large spread of
> buried radial ground wires).  For the past twelve years the ground
> consisted of one copper clad 8 foot ground rod, one 10 foot galvanized
> rod (the service entrance ground), and two skinny 4 foot ground rods
> that are now a pile of rust, all tied together at odd distances (for 1/4
> wave spacing elimination).
>
> This mobile home park is a HIGH NOISE dark hole and the existing ground
> system DID help reduce noise a great deal, though I had to water them in
> the summer to lower the noise floor.  The 'real ground was probably only
> the ten foot and eight foot ground rods.  I've never had an "RF in the
> shack problem", even when using end fed or "top loaded Tee" antennas
> against ground
>
> Anyway, today I purchased three more 8 foot copper clad rods and drove
> them in the ground.  Two spaced 30 inches apart right where the ground
> wire enters the shack (nice short cable to the under-bench ground bus).
> Another one about a foot from the old 8 foot rod, which is located by
> the North Push-up antenna pole.  The 10 foot service entrance rod is
> between the two groups of 8 foot rods.  Everything spaced out so that
> the "1/4 wave Isolation rule" doesn't come into play, that is I should
> have an effective ground for any given frequency 50KHz to 30MHz.   ONE 4
> foot rod will remain in service as it seems to be serviceable, the other
> one I drove in down to ground level.
>
> Now the question.  The total run to tie all grounds together is about 18
> feet.  I wanted to purchase some copper tubing and have a friend braze
> it to all rods in an unbroken length to tie them together.  However, the
> budget is about shot, copper tubing is out of the question for now.  I'm
> presently using odd lengths of 18Ga stranded wire for TEMPORARY use
> (yeah, I know, not the best for RF circuits).
>
> I know that they frequently use aluminum wire for electrical service
> grounds.  Anybody see a problem using it in this application?  Perhaps
> it's not as good as a heavy gauge single strand copper wire for RF, but
> just might be better than I now have.  I could then have one continuous
> unbroken run for the ground, at least until I can perhaps do the copper
> tubing and braze job later. . .
>
> By the way, the addition of three new ground rods, even with funky
> wiring interconnects already made a HUGE difference in the noise floor
> at LF and the BCB!!!
>
> -- 
> 73 de Phil,  KO6BB
> http://ko6bb1.multiply.com/ (OTR Blog)
> http://www.qsl.net/ko6bb/  (Web Page)
>
> RADIOS:
> Grundigs: Satellit 750 (2011), S-350 (2006)&  G6 (2011).
> Icom: R-75 with Two 250Hz CW Filters.
> Kenwood: TS130S Transceiver (circa 1980).
> Radio Shack: DX-380 digital portable (circa 1990).
> Yaesu: VX8R Quad-Band HT (circa 2010).
> Zenith: Royal-7000 Transoceanic (circa 1969).
>
> ACCESSORIES:   Homebrewed LF Pre-Amp, MFJ-949E HF Tuner
>                Homebrewed 6 Hz Filter.
>
> ANTENNAS: 88' Long Ladder-line fed dipole, Apex at 35 feet.
>           Amplified Mini-Whip up 29 feet for LF/MW
> Merced, Central California, 37.3N 120.48W  CM97sh
>
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