[time-nuts] Thunderbolt cabling questions

[Chris Albertson]

I did that once and thought the bends in the pipe looked ugly.  I wanted a
simple vertical mast.   The simple mast is also stronger because I can use
"U" bolts to secure it to a rafter and a floor joist that are about four
feet apart.  Results in the very strong installation.   It is build exactly
like a plumbing vent, just a long pipe with the last few feet above the
roof.  The coax run is completely 100% out of the weather.


On Sun, Jun 10, 2012 at 7:06 PM, DaveH <info at blackmountainforge.com> wrote:

>
> > The easy way to mount the antenna:
> >
> > Head over to Home Depot and get a 1" Tee, a 1" flange, a 1"
> > nipple, a 12" to 18" 1" pipe, and a 6" long 1" pipe.
> >
> > The antenna goes on top of the 18" pipe. That screws into the
> > tee. The bottom of the Tee gets the 6" pipe. Coax runs
> > straight through the 18" and 6" pipe. Nipple goes to the
> > flange and the tee. Flange mounts to the house. If you need
> > to get a bit further out,  change out the nipple for a piece of pipe.
> >
> > Spray paint it all black ( or what ever) and move on.
> >
> > Bob
> >
> > On Jun 10, 2012, at 7:43 PM, Jim Lux wrote:
> >
> > > On 6/10/12 4:24 PM, Chris Albertson wrote:
> > >> On Sun, Jun 10, 2012 at 2:50 PM,<bg at lysator.liu.se>  wrote:
> > >>
> > >>> ... 3m
> > >>> of antenna cable is no problem. Antenna position is more
> > important than
> > >>> the exact type of antenna. I'd rather have a decent
> > antenna at a very good
> > >>> site, than a very good antenna at a slightly worse antenna site
> > >>
> > >>
> > >>
> > >> 3M is trivial.  30M will work fine too.
> > >>
> > >> I agree about the location really mattering more than
> > anything else.  What
> > >> I did was drill a 2" hole through the roof up from the
> > attic and push a 10
> > >> foot gallanvised iron plumbing pipe up.
> > >
> > > you would probably want appropriate flashing around that to
> > prevent water (and vermin) ingress.
> > >
> > >
> > > The antenna sits on thop ithe
> > >> pipe and is higher then the roof top ridge and then the
> > cable go down the
> > >> center of the pipe.  I pipe flange on top  of the pipe
> > makes a perfect
> > >> mounting platform.   I used a timing antenna comes inside
> > a white pointed
> > >> plastic radome.  These sell for just under $30 on eBay.
> > Maybe it is
> > >> coincidence or not but the four holes pin the standard
> > pipe flange match up
> > >> with the four holes in the bottom of my antenna and there
> > is enough room
> > >> inside the hole in the center for an "N" connector.   It
> > is worth getting
> > >> the antenna "done right" because it is the most important
> > part of the
> > >> entire system.     Those dome type antenna are worth it.
> > the shape is
> > >> designed to shed both bird poop, and snow.  Birds can be
> > an issue with a
> > >> flat top antenna, no snow here.
> > >
> > > You probably get snow every few decades (it snowed in
> > Malibu a couple years ago, for instance), but I wouldn't
> > worry about snow loads, even so. <grin>
> > >
> > >
> > > HOWEVER, your scheme is going to be tricky to pass muster
> > with the National Electrical Code.  Two aspects need attention:
> > > You need to have a ground wire from the mast to the ground point
> > > and
> > > You need to have some form of ground of the coax shield at
> > the point where the coax enters the building.  (a "listed
> > antenna discharge unit" is the usual way).
> > >
> > >
> > > While Southern California isn't exactly the lightning
> > capital of the world, we do get some.  A bigger concern (and
> > the primary reason for the code requirement) is that above
> > ground power lines can come down and touch your antenna.
> > >
> > > And someone living in a more lightning prone area is going
> > to want to take those precautions.
> > >
> > > The installations I've seen typically use the same general
> > "pipe" scheme  (using rigid conduit, which looks a lot like
> > pipe, but has a smooth inside with no burrs) to a box on the
> > roof, and then regular conduit running down the outside of
> > the building.  Then at the point of entrance, the ground
> > bonding conductor goes from the conduit to ground, and
> > there's a coax grounding block in a box at the place where
> > the hole in the wall is.
> > >
> > >
> > > Granted, if lightning does hit, everything connected to the
> > antenna is going to fry, unless you have some sort of
> > reradiation scheme to provide an air gap.  That's what we do
> > when we test GPS receivers destined for space, where you
> > don't want to take the risk of killing the expensive flight hardware.
> > >
> > >
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-- 

Chris Albertson
Redondo Beach, California