Shack Earth. Peter Sumner, VK5PJ
A sometimes forgotten part of a ham’s shack is the earthing system, I
must admit I had only made half hearted attempts at a good station
earth in the past. Which is odd as my previous work life had a
large component of making sure all gear was properly earthed. I
am not sure if it was the cost of heavy copper cable and copper bar
stock that put me off the scent but I just always seemed to find a
reason not to do it.
About 18 months ago I had a light globe moment, why try and use all
these fancy earth bars when I had some left-over copper GAS pipe (19mm
O/D) in the shed. A scheme was hatched to use commonly available
parts from a hardware store to make a shack earthing system that could
be flexible to use and not break the bank.
My operating area is in an L shaped desk so I bought a 19 mm copper
elbow to combine with my scrap 19mm pipe, some heavy duty solder and
borrowed a small gas torch as my old BIRKO soldering iron was not up to
the task, plus a handful of copper saddles to fit the 19mm pipe but not
in the traditional way.
Now the method I settled on to attach each bit of the radio gear was to
us the copper saddles soldered along each leg of my L shape of pipe as
the connection points for flying leads to each piece of radio gear,
with the pipe mounted on the back of the desk and earth leads passing
through existing holes to the gear. I firstly measured, cut
and soldered my two pieces of 19mm copper tube into the 90 deg bend so
I could take it to the shack and mark on it where I needed the
connection points to be. Some areas of the shack had lots of gear
grouped close together so multiple copper saddles (attached in the
opposite direction to what you would to secure the pipe to the desk)
were needed in those spots.
Looking back at it I should have used a pop rivet through each saddle
to help locate it on the pipe as soldering of the multiple copper
saddles in some areas became tricky when I could not control the heat
from the gas flame. This resulted in a number of oddly angled
saddles as they slipped around the pipe when the heat was on.
Note to self, do not do it like that again.
Clean up each saddle and the locations on the pipe where they are to
go, then I tinned each of the inside surface of the saddles and then
tinned each location on the pipe where the saddles went, This was
a bit messy but effective. As I mentioned earlier a pop
rivet through the U of the saddle and the pipe probably would have been
a good way to keep each saddle in the right spot when the heat was
applied.
At the end of the copper pipe nearest to my wall (exit point), I
flattened the copper pipe using my vice and hammer to create a TAB that
I could drill an 8mm hole to attach my cable out to the copper coated
earth spike (bought from bunnings) just outside the shack wall.
For the flying lead used between the rear of the radio gear and the
earth system, the cable chosen was from the RS components catalogue as
it has a high stand count in the cable (84 strands of 0.3mm) to ensure
the cable is super flexible with a cross section of 6mm squared , which
was one of my main criteria for the cable. In retrospect this is
where I blew my budget as I could have settled on a lower spec cable
but once again my previous work experiences drove this choice for
flexibility, size and colour. Our old Quality Assurance person at
Jindalee would have been happy with my cable choice for once.
The cable from the end of the copper pipe to the earthing rod was a bit
of a fluke, I was given a short length of left over cable from a
commercial transmitter’s earth connection install and had hidden it
away for a one day project, this proved to be ideal for the purpose BUT
on the flip side I could have used multiple runs of the more common
household earth cable in a bundle, there is nothing that says it has to
be ONE cable. For the main connecting LUG to the earth rod, I
visited my local car parts people and bought a heavy duty crimp lug to
fit the cable I had. If you chose the multi cable bundle then you
could use a similar cable lug or many smaller crimp lugs, there is no
strict best way here, it is all about getting a low resistance
connection. You must remember this earth is not there to carry
high current, just to provide a low impedance path between the radio
gear and provide a common earth point for the shack equipment.
Pic-1
Two of the copper saddles ready for connections to the radio gear
soldered onto the earth pipe
Pic-2
Saddle for connections and the 90 degree bend to fit the rear of my
operating desk
Pic-3
All items soldered, now time for a cleanup
Pic-4
Earth system in use, showing the pigtales that connect to the radio gear
Pic-5
Corner of the earth system mounted on my home made operatoins desk
Pic-6
Heavy copper cable off to the earth rod outside the shack wall.