[time-nuts] Thunderbolt cabling questions
DaveH
info at blackmountainforge.com
Mon Jun 11 02:06:50 UTC 2012
And make sure that the flange is being bolted into a stud and not just the
sheathing. A good gust could pop it off especially if the arm is long.
Great idea though!
Dave (who just got a Tbolt and waiting on an antenna) I am doing a tower
for my ham radio stuff and want to put the Tbolt on the other side of the
house to gain some isolation.
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Camp
> Sent: Sunday, June 10, 2012 17:53
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Thunderbolt cabling questions
>
> Hi
>
> Sorry for the blank.
>
> 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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