Other than the choice of #6~#4 as a jumper, I have no
disagreements with Guy. I would still advocate the use
of wide copper strap. If a round member is desired, I
would use nothing smaller than #2. If you can find the
#6 the power co uses, you can use a weaver or split-bolt
clamp to create your bond.
73,
Bob AA0CY
----------
From: Guy Olinger, K2AV[SMTP:k2av@contesting.com]
Sent: Wednesday, November 03, 1999 12:23 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Another GROUNDING question.
NOT a good idea to use water pipe as an elevated ground. What you have
done with the water pipe is spread the RF through the house. It
probably radiates a good deal.
Sink a ground rod(s) outside as close as you can to a short vertical
run from the shack. Call it the RF Ground. Wide strap to this ground,
as mentioned in prior post is good. Do NOT attach to the water pipe or
any other conductor. Run a # 6 or # 4 wire from this rf ground right
at the rod(s) via shortest possible path to the power ground, buried
outside if possible, and bond them together. This bonding to the power
ground is REQUIRED.
If you have a single 120v cord to an outlet that feeds the
radio/computer gear (at my place a string of MOV'd multi-outlet power
strips that go to a single wall outlet). Take off the plug on the cord
to the wall. Get six or seven winds around a toroid, and replace the
plug. Do the same for a 220 volt or separate feed for the amp. Don't
have any connection to the house neutral conductor other than the
toroid wrapped conductors. These steps will get rig-slop RF off the
power wiring.
Do something similar for the phone line and any control lines for
rotators/switches, as close to the radio setup as decently possible
(this in addition to any Polyphaser, etc, grounding devices where it
comes in to the house. The Polyphaser ground MUST also be bonded to
the power ground as above. You're lucky if some of these paths are
shared, or (oh joy!) they're all at the same spot.
Where the coax leaves the radio setup for the antennas, put
common-mode isolators on all the coaxes (RadioWorks T4 or the like --
WireMan bead balun kits may be ok, but might not be enough). You may
get better results by putting the T4's (or ...) at the amplifier
input/output.
The above will leave the path to the outside RF ground as the only
place for the stuff to go. This also means that all the copper strap
station ground bus will be at the same RF voltage.
Remember, it is the voltage DIFFERENTIAL that gets into things.
Otherwise the local AM radio station would light you up. (RF on the
modem case connection, and phone line like an antenna, means RF flows
through the modem on the way to the "antenna". If rf is blocked on the
phone line with a toroid at the modem, no antenna, no flow. Likewise,
transmitted energy from antenna outside cannot use the phone line as
an antenna, thereby presenting a differential through the modem to the
station connections. Note this phenomena is a two way problem. An RF
block cleans up both directions.
Good luck & 73 from a long time 2nd story shack man.
On Wed, 3 Nov 1999 10:20:28 -0800, you wrote:
>
>A good lightning ground is a good RF ground, but the converse
>isn't necessarily true.
>
>Make sure the cold water pipe is continuously metal and doesn't
>become PVC soemwhere. Also jumper all joints to prevent crud
>buildup from increasing its resistance, the water meter likewise must
>be jumpered. This last step may require a licensed person to do the
>job, so check the municipal requirements. Although the cold water
>pipe doesn't hit ground for a fair distance, it still carries the current
>with minimal inpedance (to any other medium). You should consider
>changing the #6 to at least #2; 2/0 would be better; and 1-1/2"-wide
>(or wider) copper strap would be the best medium for that jumper.
>
>73,
>Bob AA0CY
>
>----------
>From: N6CW@aol.com[SMTP:N6CW@aol.com]
>Sent: Wednesday, November 03, 1999 9:44 AM
>To: towertalk@contesting.com
>Subject: [TowerTalk] Another GROUNDING question.
>
>
>I have been reading with great interest all the comments about grounding a
>station. My question deals with grounding when it is not possible to have a
>short ground from the rig to ground. My station is located on the second
>floor of my house. My current ground system consists of a single 5x2 foot
>copper sheet bolted on the back of my desk which all electronics are grounded
>to, and conected to, a single 3 foot long #6 wire running through the floor
>to a copper cold water pipe directly under the floor and in the garage
>ceiling. This cold water pipe runs all over the house and probaly does not
>get into the ground for 50 feet or so.
>
>The good news is that I do not have any problems with RF getting into my
>equipment. I do have some problems with RFI into phones and on the low bands
>I do have some audio rectification in the TV set. And when I force my antenna
>(CC X7) to work on 18 and 24 MHz I have probelms I dont have with it on the
>resonant bands. Probably this has nothing to do with a poor ground BUT I FEEL
>like this ground is not good enough.
>
>So what do people do with an above ground level shack do to insure they have
>the best ground possible? I realize I am talking about two different ground
>situations here. An RF ground and a single point station ground. Since I dont
>have RF getting into my equipment possibly this is an adequate ground for
>this purpose. And since I dont have any way to shorten the length of the
>ground cable/pipe then maybe I have all I can expect?
>
>Comments appreciated.
>
>Terry/N6CW
>
>--
>FAQ on WWW: http://www.contesting.com/towertalkfaq.html
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--. .-..
73, Guy
Guy Olinger, K2AV
k2av@contesting.com
Apex, NC, USA
--
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Search: http://www.contesting.com/km9p/search.htm
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Problems: owner-towertalk@contesting.com
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