[time-nuts] Thunderbolt cabling questions

[DaveH]

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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