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The following is summary of the replies I received to my question about
grounding 1/2 CATV hardline to my Rohn 25G tower. Many thanks to all who
replied!
73 de Mike, AD4VH
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On Oct. 18, I wrote:
I am interested in a good method for grounding a piece of 1/2" CATV hardline
as it passes the base of my tower. I would like to get a good solid
connection, but am concerned that anything that clamps to the hardline
asymmetrically will deform or crush the relatively soft aluminum outer
conductor. The cable is jacketed, so the fixture in question would
necessarily have to open wide enough to accomodate the extra diameter of the
jacket if it were to be slipped over the end. Alternatively, I was thinking
that with something like a pair of clamp shells, they could be placed at the
ground point directly without having to feed thru the 30 remaining feet of
cable.=20
Anybody solved this problem already? I am hoping the there is some little
gizmo waiting for me at the local hardware store that will do the job
directly without the need for alot of modification.
73 de Mike, AD4VH...................
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Jay, WX0B wrote:
Hows this for size,
slice the cover off the heliax/hardline at the base of the tower.
Use an aluminum strap you have made from some AL thin stock and clamp=20
into place with a stainless steel hose clamp. You should not use copper=20
strap because of galvanic actio.
place another stainless steel hose clamp around the tower leg to protect=20
the galvanization from migration and place the Aluminum strap on top of=20
it. Secure in place with another Stainless hose clamp on top of the=20
whole sandwich. Should work fine. I would also use NALOX (tm) at all=20
junctions to prevent AL oxide. =20
I would use 3M (tm) Vapor wrap to seal it all up and tape.
GL
Jay
If you find a better way copy me please.
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Dick, WJ0M wrote:
SNIP...
Hi Michael, I use =BD CATV hardline as well. It runs into a modified
electrical distribution panel for switching. Where it goes into the
panel, I've used brass plumbing hardware, ... can't recall the proper
names, but it's the same as what you'd use for copper pipe. When
fittings are tightened, it locks the feedline in place. Also use a
combination of those fittings and a modified barrel connector to get
from hardline to flex. If you desire more detail, I can check the
hardware store for the proper names and a better explanation. Clear as
mud??
CUL, 73
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J.P., AA2DU wrote:
Michael:
Polyphaser in Linden, NV, makes a device such as you are seeking.
They clmap the tower leg and the hardline shield and bond them together
to ground. I don't remember their number off hand, but they advertise
in most of the ham mags.
73, J.P. AA2DU
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Bill, KM9P wrote:
I just wrapped several wraps of braid around it and it acted like a
dampening to the force of the clamp.
73
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Pete, N4ZR wrote:
Mike, I use a bronze clamp of the sort made for clamping electrical ground
wires to house plumbing. They come in various sizes and seem to squeeze
pretty symmetrically. The teeth cut into the aluminum jacket of my hardline
(granted 3/4", not 1/2") nicely with very little pressure and no evident
deformation.
73, Pete Smith N4ZR
n4zr@contesting.com=20
... and not changing!
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Chuck, KE5FI wrote:
I would be interested in the answers you get. I will be using this type=20
cable soon.
My soloution would be to cut away 1" of rubber and solder to the=20
aluminum. Then cover the whole thing with a sealant.
Chuck
ke5fi@wt.net
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Bill, AA4NU wrote:
Mike .... I.C.E. offers "grounding blocks" like you need, Also
Polyphaser offers straps to do the same ...
Hope this gets your pointed in the right direction !
=20
73 Bill AA4NU
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Jim, KC8MK wrote:
Mike,
Go to the hardware and get a stainless steel hose clamp.
Use some penetrox and whatever wire you are going to use to
ground it with.
Tape the whole mess up when you are done.
Scotch 130C and 88 will do the job.
73, Jim
P.S. Look for you on 160 this winter.
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Denny, K8DO wrote:
Get a block of aluminum about 2.25" square... have a local machine shop=
drill
two holes through it.. one hole to be the right size to clamp to the leg of
the tower (or ground rod as the case may be) and the other to clamp to the
hard line (sans jacket).. then they can saw half blocks out of this to=
form
clamps, add 3/16" clamp bolt holes, and you are in business...
I get my aluminum from:
Dillsburg Aeroplane Works
Dillsburg, Pa
717/432-4589=20
Cheers ... Denny k8do@aol.com
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Roger, K2JAS wrote:
like Denny's (k8do@aol.com) idea about machining a block of aluminum and
I'm sure that the people he recommended for the aluminum stock would have
this material:
Dillsburg Aeroplane Works
Dillsburg, Pa
717/432-4589
I've seen their catalog and it is comprehensive regarding just about
anything you could ever want in aluminum tubing and supplies. However, be
prepared for a substantial bill.
Again, allow me to recommend that you (or for that matter anyone) check out
your nearest scrap metal recovery yard. It has become one of my most
favorite places to visit. Aluminum, steel, stainless, copper, tubing,
piping, wire and cables...
and believe it or not working electronic equipment too (sold by the weight)!
You name it, it's a "gold mine" not only for what's available but the prices
are ridiculously low.=20
Today I picked up about 40 feet of a oil and gasoline resistant jacketed
stranded copper cable. The diameter of the copper was easily 1/2 inch plus.
It weighed 12 pounds. I think I overpaid but it only cost $10 with some
other pieces of alunimum. It will make a magnificent grounding cable to run
from my roof mount tower down the side of the house to a buried 8-ft ground
rod. Two copper clamps for this cable cost me over $6 at Home Depot!
The scrap metal yard may never have exactly what you want because things
just keep coming and going. You just have to make it a habit to stop by
every once in a while and check out the stock.=20
73's, Roger
K2JAS@worldnet.att.net
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J.P., AA2DU wrote:
Hmmm...I'm no metallurgist but I was always taught that aluminum and
galvanized steel don't mix. That's the very reason that the use
of aluminum jacketed "CATV" hardline is not recommended for runs
going up the tower.
Polyphaser makes an excellent set of feedline to tower grounding
systems that use different metals depending on what you attach them
to. One end might be copper or aluminum and the other could be
compatible with the galvanized steel of the tower leg.
73, J.P.
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Mike, NS7Z wrote:
Industrial Communication Engineers (ICE) sells a tower mount ground block=20
that attach's to the legs w/ U bolts. You specify the drilled hole size=20
or describe your coax and they will drill the holes to match the shield=20
OD, less the covering. It is all stainless stell and not to costly.=20
They are in Indianopolis , Indiaana
73 de Mike NS7Z
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Rich, KE3Q wrote:
I'd think it'll work fine as long as you don't overtighten whatever you=20
clamp around it. It's common to use a hose clamp (stainless preferred)=20
and a wire or braid to the ground at that point. It'd be very difficult=20
to overtighten a hose clamp so as to deform the coax. Goop the whole=20
connection up with waterproofing stuff.
73 - Rich Boyd, KE3Q
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Steve, N0YVY wrote:
I would use homemade clamps. I start with a piece of 3/4 inch aluminum plate
about=20
2 inches square. I drill the appropiate size hole through the plate for the
aluminum=20
jacket. Then I flip the piece 90 degrees and drill two 11/32 holes on each
side of=20
the center hole and perpendicular to it through the edge of the plate for
the 5/16=20
inch clamp/mounting bolts. Then I saw the whole thing in half and the saw
cut provides=20
about the right crunch. Depending on where it is going, I may make the
clamp/mounting
spacing fit a U bolt and then grind/file radious to fit tower leg. When
clamping to a=20
tower leg, I would use a stainless steel bolt, and a thin piece of stainless
sheet between
the aluminum block and the galvanized tower leg with lots of anti-ox
compound. Then
seal the clamp, leg and cable like it was a coax joint to keep the water=
out.
No moisture means no electrolysis.
It is cheap and takes me about 15 minutes to make with a drill press, band
saw and grinder.
de n0yvy steve
____________________________________________________________________________=
___
Michael Tope, AD4VH (ex KD8NS) =20
200 Easy Street =20
Melbourne, FL 32934 =20
Phone: (407) 259-7494
Eail: mtope@iu.net
____________________________________________________________________________=
___
"It is the empty space inside the vessel that makes it useful" - Lao Tzu
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