But in practical terms, how do you get a "perfect" earth ground reference
for the analyzer to use when making the measurement?

===================================

You don't need a "perfect earth" because that is precisely the quantity you
are trying to measure.

The only "perfect" thing is the 36 ohms which is the calculated value of the
1/4-wave antenna's radiation resistance.

But it is not essential to have an antenna as tall as a quarterwave to find
the earth-loss resistance. There's not many people who can erect a 1/4-wave
vertical at 160 meters.

The 'perfect' radiation resistance of an antenna shorter than 1/4-wave is
given with sufficient accuracy by -

Rrad = Square( 24 * Height / Wavelength ) ohms.

Of course, an antenna shorter than 1/4-wave has reactance. But this can be
tuned out with any coil which has a negligible loss resistance compared with
antenna resistance.

Make the measurement at the resonant frequency of coil + antenna whatever it
may be. The antenna analyser will tell you when you are at resonance. Vary
frequency for the minimum pure resistance. And that is the resistance you
are looking for.

The lower the measurement frequency the more easy and accurate the
measurement provided it is not overdone. The earth resistance measurement
doesn't have to be made at the same frequency the antenna is to be used at.
It can be appreciably lower.

The great advantage of these one-hand held, battery-driven, antenna
analysers is that the connecting wires can be kept very short, ie., much
shorter than a 1/4-wavelength.

They are sufficiently accurate for this sort of job. And don't be afraid of
lying on your belly to read the meter. The best things since sliced bread.
---
Reg, G4FGQ.

"Reg Edwards" wrote in message
...
I should have mentioned. When measuring signal strengths as a measure of
performance there's safety in numbers. Take the average of a fair number
of
transmissions, all well above the noise level, at about the same time each
day, using your most stable S-meter with the receiver gain turned down
such
that the meter deflection is on the most sensitive sector of its scale.
Allow the receiver to warm up for the same length of time on each occasion
it is used.

S-meter calibration doesn't matter two hoots.

And once set, don't ever touch the receiver gain control.

You should take all these precautions from the time when you have laid
only
one radial. You will not wish to dig up already laid radials in order to
re-measure the earlier ones you forgot to treat in the standard manner.

It will be appreciated, to make tests during radial-laying operations by
asking for signal strength reports from your many friends, using THEIR
S-meters, will result in you losing them.

Incidentally, when "I" used this method of testing antenna efficiency I
stopped at 8, 10 feet, radials with a 3 feet rod at the end of each. This
included the domestic incoming main water pipe which made no difference
when
THAT was connected. So I stopped.

But my soil resistivity is only about 70 ohm-metres. I can grow anything
in
my garden. At present it is covered with a dense growth of 3 feet high
weeds except for a small patch which I use to feed the birds. As if they
didn't get enough to eat anyhow. With the trees and overgrown bushes it
is
a wild-life sanctuary for frogs, rats, squirrels and hedgehogs. The only
complaints I get are from the neighbours. But its stopped them
complaining
about TVI.
---
Reg, G4FGQ


Sounds a little like my counterpoise. 12 wires 12ft long, Short ground rod
at far end of each wire just to pin it down. 10ft 2inch pipe in the middle
for ground/ mount. You can get an idea of resistance to ground by
connecting 120 VAC to the ground system through a fuse and see how big of a
fuse you can blow. I rigged a fuse holder with a neon blown fuse indicator
to a piece of PVC pipe. last time I checked mine it would pop a 10amp fuse.

"Bill Turner" wrote in message
...
On Fri, 03 Sep 2004 17:19:26 GMT, "Jimmie"
wrote:

You can get an idea of resistance to ground by
connecting 120 VAC to the ground system through a fuse and see how big
of a
fuse you can blow. I rigged a fuse holder with a neon blown fuse
indicator
to a piece of PVC pipe. last time I checked mine it would pop a 10amp
fuse.

__________________________________________________ _______

Remember the movie "Dumb and Dumber"? This is the electronic version.

--
Bill, W6WRT
QSLs via LoTW

Thats what I thought the first time I saw it done but this is the way the
power company checks grounds. It can be done in a safe manner. Also there is
equipment commercially made for doing this test. Ideally one should use this
approved equipment but there is no reason it cant be done with improvised
equipment with no more risk than taking a voltage measurement in a hot
chassis. Of course there are those who lack the ability to safely perform a
test like this and should not even be allowed in their service panel to
reset a breaker.

"Bill Turner" wrote in message
...
On Wed, 08 Sep 2004 14:51:10 GMT, "Jimmie"
wrote:

Thats what I thought the first time I saw it done but this is the way the
power company checks grounds.

__________________________________________________ _______

I can't believe a power company could be dumb enough to blow a fuse to
measure (?) ground resistance.

A much better way would be to use either a variac or a current-limited
source and calculate the resistance with Ohm's law.

In what way better, They are not interested in a specific value in most
cases. Just a go -no go test. Plug the tester into an outlet, touch it to
the ground stake after isolating ground from neutral. Fuse pops or it
doesnt, Ground meets spec or it doesnt. Apparently there are lot of people
who think this idea is not so dumb since the tester they use is commercially
available, a fact that I mentioned in the previous post that you chose to
ignore.

--
Bill, W6WRT (founder of the Society to Prevent Fuse Abuse)
QSLs via LoTW

On Wed, 08 Sep 2004 21:24:53 GMT, "Jimmie"
wrote:
They are not interested in a specific value in most cases.
....
Ground meets spec or it doesnt.

Without a specific value, how do they (we) know it meets spec?

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Wed, 08 Sep 2004 21:24:53 GMT, "Jimmie"
wrote:
They are not interested in a specific value in most cases.
...
Ground meets spec or it doesnt.

Without a specific value, how do they (we) know it meets spec?

For a mains safety ground, the bottom line is: is the ground resistance
low enough to blow a fuse in the live rail? If the answer is no, you're
heading for a fire, so there is some surety in verifying that a fuse
really will blow.

On the other hand, for an RF ground it's a lousy test.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Ian White, G3SEK" wrote in message
...
Richard Clark wrote:
On Wed, 08 Sep 2004 21:24:53 GMT, "Jimmie"
wrote:
They are not interested in a specific value in most cases.
...
Ground meets spec or it doesnt.

Without a specific value, how do they (we) know it meets spec?

For a mains safety ground, the bottom line is: is the ground resistance
low enough to blow a fuse in the live rail? If the answer is no, you're
heading for a fire, so there is some surety in verifying that a fuse
really will blow.

On the other hand, for an RF ground it's a lousy test.

True enough on the RF , but no worse than any other test meant for primary
power. While this test alone does not insure a good RF ground and it is a
good first test to let you know you are going in the right direction. If
this test is bad for 60Hz AC then RF ground is probably a lot worse. VSWR
reading for my antenna is 1.25:1 at the resonant frequency of my antenna.
Given the inaccuracies of SWR meters I figure I have a ground resistance
some where between 3 and 10 ohms. Maybe one day I will try to to get a more
accurate reading when other things in my life take less priority.



--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Thu, 09 Sep 2004 13:11:02 GMT, "Jimmie"
wrote:

VSWR
reading for my antenna is 1.25:1 at the resonant frequency of my antenna.
Given the inaccuracies of SWR meters I figure I have a ground resistance
some where between 3 and 10 ohms.

Hi Jimmie,

How do you figure that?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Thu, 09 Sep 2004 13:11:02 GMT, "Jimmie"
wrote:

VSWR
reading for my antenna is 1.25:1 at the resonant frequency of my antenna.
Given the inaccuracies of SWR meters I figure I have a ground resistance
some where between 3 and 10 ohms.

Hi Jimmie,

How do you figure that?

73's
Richard Clark, KB7QHC

Mostly an educate guess, my AC test blows a 10 amp fuse to smithereens so I
figure less than 10. SWR is 1.25 to 1 This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring 37
or soo for this. I know its a lot of by guess and by golly and I am aware
that there are better ways of finding out what the ground loss really is
but I'm not so anal that I reallly care. Given the SWR reading I figure
closer to 3 and a neighbor recently had lightning rods installed and the
installers measured theire ground resistance at 2.5 ohms so I am pretty
confident of my educated guess .

When I get my tower up 20 meters will be on a beam on top of the tower and I
plan to use the ground plane with a 40 M vetical 1/4 wave antenna. Ground
plane is made of 12 wires 12ft long connected to a 10 ft ground rod at the
base of the antenna. Do you think I should modify the ground plane. I was
thinking of at least adding 4 wires 1/4 wl long for 40, I really think this
may be a waste of time though. Also would existing ground plane be good for
80M.

On Thu, 09 Sep 2004 19:42:41 GMT, "Jimmie"
wrote:

This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring 37
or soo for this.

Hi Jimmie,

So you have no radials?

73's
Richard Clark, KB7QHC