On 09/09/2018 22:32, Bob Wilson wrote:
... There was a lot of hum out of the system with a 300 watt
audio amp feeding the speakers!


Somewhat reminiscent of the opening sequence in
one of the Back To The Future films!

Or, going back some years to the April Edition
of Wireless World and the article by the
Dutchly-named George Izzard O'Veering.

Bob Wilson wrote:
Yet another ground to contend with is whatever may come with a cable TV
connection. (Sorry for my ignorance, I am not sure how to translate for
the other side of the Atlantic! In the US we typically have a 75 ohm
coax coming in for this purpose.) At another residence I had about 3
volts between that ground and the ground for AC power.

A modern cable TV demarcation point has galvanic isolation.
With a TV there usually is no problem because it usually has galvanic
isolation in its input circuit as well (some ferrite bead transformer
between the input and the tuner).

For radio tuners that may be different.

On 06/09/2018 13:59, Rambo wrote:
On Thu, 6 Sep 2018 11:46:55 +0100, Gareth's Downstairs Computer
wrote:

Unearthed the previous fan of plumbers' copper microbore tubes
and associated ground rod to find a corroded and non conductive
mess and raised the question of how to protect underground
junctions from the worst that nature could throw at them?

Firstly, resurrecting a technique from school metalwork lessons
from 53 years ago when brazing things together, dig out the
gas torch, soldering flux***** and solder and connect all together
electrically.

Secondly, to protect the now-relatively-massive joint, smear with
petroleum grease. Was this a good idea, and is there something better?

***** Curious as to whether could be combined with one's radio
interest to nake a flux capacitor to go time travellingg :-)


cathodic protection?


Galvanising !
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On 06/09/2018 16:39, Catweazel wrote:
On 06/09/2018 13:59, Rambo wrote:
On Thu, 6 Sep 2018 11:46:55 +0100, Gareth's Downstairs Computer
wrote:

Unearthed the previous fan of plumbers' copper microbore tubes
and associated ground rod to find a corroded and non conductive
mess and raised the question of how to protect underground
junctions from the worst that nature could throw at them?

Firstly, resurrecting a technique from school metalwork lessons
from 53 years ago when brazing things together, dig out the
gas torch, soldering flux***** and solder and connect all together
electrically.

Secondly, to protect the now-relatively-massive joint, smear with
petroleum grease. Was this a good idea, and is there something better?

***** Curious as to whether could be combined with one's radio
interest to nake a flux capacitor to go time travellingg :-)


cathodic protection?


Galvanising !

Can't see how to do that when it's all still in the ground with just
the ends showing :-)

On 9/6/2018 5:46 AM, Gareth's Downstairs Computer wrote:
Unearthed the previous fan of plumbers' copper microbore tubes
and associated ground rod to find a corroded and non conductive
mess and raised the question of how to protect underground
junctions from the worst that nature could throw at them?

Firstly, resurrecting a technique from school metalwork lessons
from 53 years ago when brazing things together, dig out the
gas torch, soldering flux***** and solder and connect all together
electrically.

Secondly, to protect the now-relatively-massive joint, smear with
petroleum grease. Was this a good idea, and is there something better?

***** Curious as to whether could be combined with one's radio
interest to nake a flux capacitor to go time travellingg :-)



I don't know how to protect it, I recently installed ground rods and
figure to periodically test them and replace as needed.
I ran a 253ft BOG antenna, I needed a ground at each end.
I started with 1-five ft 1/2" copper pipe, with predrilled 1/8" hole
running down and around the pipe. I used the method on page 25 of this
pdf to measure the ground resistance.
http://www.weschler.com/_upload/site...owntoearth.pdf

I had a pair of wires ran from my home to each end of my BOG antenna
so it was convenient to connect it to a variac driven by an isolation
transformer. I used that as my voltage source*. I set it at about 40V,
but measured the voltage at the ground rods for calculations, because
of the voltage drop of the feed wire.
My first measurement was 112 ohms, both ends 253 apart were basically
the same even though I had 3 rods at one end and 1 rod at the other. I
added 2.5lbs of Calcium Chloride at one end by pouring the water/Calcium
Chloride solution into the three copper pipe ground rods. After a few
hours a retest showed a drop from 112ohms to 73 ohms. The next day it
was down to 60 ohms. About a week later I added another 3.5lbs of the
Calcium Chloride solution into the copper pipes, this brought the
resistance down to 34 ohms.
I added 2 more rods to the other end and added more Calcium Chloride,
that brought the end down to 24 ohms.
The measurement at one end 22.35V and 660ma for 33.9 ohms.
The other end 13.14v and 580ma for 23.9 ohms. Lower voltage because my
240ft feed line was a much smaller gauge and had more voltage drop.

* I know 60hz drive voltage is not ideal but, I didn't have a signal
generator with enough power do the job.
http://www.esgroundingsolutions.com/...stance-meters/

There are some papers saying DC better to measure earth ground, I
don't know.

On Fri, 7 Sep 2018 09:37:53 -0500
amdx wrote:


I ran a 253ft BOG antenna,

What DX did you hear with it and on what band(s)?


--
Mouse.
Where Morse meets House.

On 9/10/2018 3:19 PM, A. non Eyemouse wrote:
On Fri, 7 Sep 2018 09:37:53 -0500
amdx wrote:


I ran a 253ft BOG antenna,

What DX did you hear with it and on what band(s)?



I ran it for the AMBCB. It was clearly directional.
I'm in the Panhandle of Florida and I pointed it North.
It is a quiet antenna and the best of the 3 antennas I have.
I suspect It will work well on 160 and 80 meters, but My R-71A
has a SSB problem and until I fix that, I can't check.
Mikek

On 12/09/18 03:23, amdx wrote:
On 9/10/2018 3:19 PM, A. non Eyemouse wrote:
On Fri, 7 Sep 2018 09:37:53 -0500
amdx wrote:


I ran a 253ft BOG antenna,

What DX did you hear with it and on what band(s)?



Â*I ran it for the AMBCB. It was clearly directional.
I'm in the Panhandle of Florida and I pointed it North.
Â*It is a quiet antenna and the best of the 3 antennas I have.
I suspect It will work well on 160 and 80 meters, but My R-71A
has a SSB problem and until I fix that, I can't check.
Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* Â* Mikek
is this called earth bounce ?