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

"Richard Clark" wrote in message
...
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?

Yes I alreaady described it once in this thread.
73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
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?

Described the radials once but that text has been snipped.

12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in place.
73's
Richard Clark, KB7QHC