[MLB-WIRELESS] Making a roof mounted antenna easily removable?

[Nick Sibbing]

Justin wrote:
> 
> Hi Folks,
> 
>  I bought a 5 meter length of 42 mill gal pipe on the weekend to mount to my
> roof as an antenna. I'm going to stick it through a hole in the tiles and
> use 2 U bolts a little over a meter apart to secure the bottom of it to the
> internal roof structure. The bottom of the pole will rest on the top of a
> wall frame. I've got a large stick-on rubber flashing to go over the hole in
> the tiles. The mast will be trimmed to about 4 and a bit meters over all to
> meet the councils '3 meters above the roof' bylaw.
> 
>  So, the question. How can I make the top of this mast removable so I can
> bring it down and put it up every now and then without having to undo the
> entire installation? I don't have to ruin / reseal the rubber flashing every
> time and also loosen and tighten the U bolts blah blah blah....
> 
>  Would cutting it and welding some sort of larger diameter sleeve be ok so I
> can take off only the section sticking above the tiles? I was also thinking
> cutting a slot or two in the bottom of the sleeve and using another U bolt
> to clamp it on.

I'd suggest finding another length of pipe to use as an internal sleeve
to your 42mm gal mast you'd only need approx 2m (1m inside roof cavity
and 1 m outside for the mast to slip over) then weld or clamp some sort
of stop on the innersleeve to stop the mast resting on the tiles. One
advantage of this may be that you'll be able to rotate the mast which
might be handy for aligning the antenna.

If you are just putting an omni on the end then there is probably
minimal sideways load if its a 24db pay tv antenna then the load is more
significant.  Are you going to have guy wires?

I also wonder whether any consideration needs to be given to reinforcing
the timbers in the roof. Its possible you are talking about a 1m piece
of hardwood held in place by 2 nails.

I am no engineer but it all sound pretty right what you are up to. I
tested a temporary mast and 20db pay tv antenna on my roof with a 6 m
length of 3/4 inch old gal waterpipe and one lot of guy wires and it was
fine. Your setup of only 3-5 m and vastly superior pipe for the mast
seems much better again.

Regards nick sibbing

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