View Full Version : Roof Mini-Tower or Tripod
I have seen the Glen-Martin mini towers...I like the 4.5 foot one. I guess this is what I could mount and have a rotor (Ham IV) on the inside with a "thrust bearing" near the collar. Question, who else makes these mini towers? Whats the most height I can add for a mast? Is it feasible to have the 8.5 foot Glen-Martin mini tower? Isnt it dangerous climbing this thing on a slanted roof? I used to do tower work back in my early 20's. I was never afraid of heights. It was more of the sudden "stop" thing that scared me if I fell..(LOL)
My thinking is a TH2MK3 on the bottom (maybe 3 feet above the thrust bearing) and another 2 meter antenna 5 feet or more above that. Are these too conservative? Can I go more? Can I use a 2 element Quad instead of the TH2MK3? But where would the 2 meter go?
The days of a simple dipole seem a fond memory when I consider what I am contemplating doing..
Peace
WB2WIK
08-23-2011, 10:04 PM
I have seen the Glen-Martin mini towers...I like the 4.5 foot one. I guess this is what I could mount and have a rotor (Ham IV) on the inside with a "thrust bearing" near the collar. Question, who else makes these mini towers?
Glenn Martin does, and hams work there. They're not a distributor, they're the manufacturer.
Whats the most height I can add for a mast? Is it feasible to have the 8.5 foot one? isnt it dangerous climbing this thing on a slanted roof?
I have the 8 footer on my roof right now, for the past 11 years; and I've used the 9 footer in the past also. They're very, very strong and install easily. I use a climbing belt to climb it (of course) and it's not dangerous at all; however they also tilt over in either of two directions once installed, and that's quite easy also. Mine is installed at the roof peak (ridge) and I don't find anything scary about it. The 8 footer is very strong and has legs spaced 32" apart between the mounting brackets (in both directions) so the brackets usually fall directly over roof rafters in most homes that use 16" stud and rafter spacing, so it's easy to get good attachment through the roof and directly into rafters. It will accommodate a mast at least ten feet long, and I've gone fifteen feet without issues, as long as the mast is 2" O.D. and strong.
My thinking is a TH2MK3 on the bottom (maybe 3 feet above the thrust bearing) and another 2 meter antenna 5 feet or more above that. Are these too conservative? Can I go more? Can I use a 2 element Quad instead of the TH2MK3? But where would the 2 meter go?
You'd probably have to use a longer mast for a quad, since a quad takes up a lot of "vertical" space, not just horizontal like a yagi. Unless you want the quad scraping the roof, you'd need at least the 8-foot model RT832 with at least a 10' mast installed. About 3 feet of the mast is used up inside the tower, so that will put the top of the mast 15' above the roof. Probably "just" enough. A 4-1/2 footer is too short and will not do this job. If you're using a 2m beam on the same mast, a yagi is a better option.
I use a Glen Martin 18ft tower on my roof with a TH-3JRS beam 6ft above the thrust bearing. I'm sure I could have put it up the higher, I have 3 more feet available but I wanted to be ultra conservative. I'm a big guy and wouldn't trust the tower for climbing but like Steve says, it tilts over easily and my wife, step daughter, her girlfriend and I can easily take it up and down, two on the ground pulling on a rope and two walking the tower up. See my qrz.com profile for a picture.
Here's why I have to use a roof tower.
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