[PVRCNC] recommended mast

[Mike Barts]

Jim,
The short, unsatisfying answer is, it depends.

The first step is to determine what will be mounted above the tower and how
far. DX Engineering has a handy mast load estimator tool on their website
that's a good first guess.  I'm assuming you're looking at a Christmas tree
of HF beam and VHF antenna(s). I think the rule of thumb is that the VHF
antenna(s) should have spacing about 1/2 their boom length from a lower
frequency antenna. This is where some antenna modeling would come in real
handy. You don't need to worry about the lower frequency antenna as much as
the higher frequency one above it. I'd put at least 4-5' of mast inside the
tower to the rotor so that you have room to lift the mast and antennas in
case the rotor needs replacing/repair. Chrome moly is the gold standard,
but DOM is little cheaper and almost as strong. Check the specs.

A couple of years ago, when I was building my tower, I found a guy on CL
that was bringing stuff from Fayetteville and was able to get a ~20'
2"x1/2" DOM tube for a reasonable price. I also got some 2"x 1/2" aluminum
tube for a gin pole. Unfortunately, I've lost contact with him. But its
worth looking for local sources before paying big shipping. Sorry I can't
be more helpful.

73, Mike N4GU


On Fri, Jan 18, 2019 at 8:53 AM Jim WW4M <jim.ww4m at gmail.com> wrote:

> Hi guys. I haven't been active much recently but have enjoyed reading your
> posts to the list.
>
> This past summer, due to miscommunication with a contractor during roof
> renovations, W4ATC's tower and tribander were removed and scrapped. We are
> looking into options for rebuilding at Daniels Hall or possibly finding
> another location on campus (perhaps co-located with Electrical Engineering
> on Centennial Campus). If we remain at Daniels our VHF beams have been on a
> separate mast. If we find a new location we may have to use a single tower
> for VHF beams and the tribander.
>
> We are starting the process of rebuilding and are looking for mast
> recommendations. DX Engineering has 2" chromoly steel masts but it appears
> they only come in 22-foot lengths (which could be difficult to work with
> because of the length). Texas Towers carries 2" Rohn 5-foot and 9-foot
> high-carbon steel masts and Universal Tower 6-foot, 10-foot and 16-foot
> aluminum masts.
>
> What are the hive's recommendations for mast length and material?
>
>
> https://www.dxengineering.com/search/department/towers/product-line/dx-engineering-heavy-duty-4130-chromoly-steel-masts?autoview=SKU&sortby=Default&sortorder=Ascending
> https://www.texastowers.com/catalogsearch/result/?q=mast
>
> Please reply-all to include Dan Stancil WY3O, the club's faculty advisor.
>
> 73, Jim WW4M
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I kin brain inglish and mouth it gud
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