How to mount a vertical antenna on my roof?

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From: rehm@zso.dec.com
Date: Tue Jun 06 1995 - 04:13:04 EDT


I've just purchased a Cushcraft R7 vertical (no flames please) for
broader HF coverage than my 40m-20m loop (which doesn't work well when
it's raining...the turning capacitor isn't water-proofed...)

I'm considering various ways to mount the R7 on my roof of my 1 story
house.

I've never done this before. In previous homes, I strung dipoles and
other wire antennas. I'd like the benefit of the wisdom of others how
have roof-mounted their verticals.

Givens: The R7 requires 5'-8' clearance from the roof line, and
1.5"-1.75" mast. (1.25" TV mast is too small!) R7 weighs 12.3 lbs
and is 22.5' tall.

So far: Bought the R7. Purchased a 6' length of 17 gauge 1.675"
galvanized fence post. (This was recommended by Cushcraft.)

Here are the various options I've considered:

1. Roof peak mount - it has two trapezoidal flanges that are bolted
    to 4" piece of 1-1/2 tube.

            + Simple to mount on the roof.
        + Tilts too, so tuning adjustments are easier.
          - Must find 1-1/2" mast. TV 1-1/4" mast is too small for
                the mount *and* the R7. My 6' piece of 1-5/8" fence post
                is too large.
        - Mast must be guyed with non-metallic wire since the mount
          itself is a bit flimsy. Source for non-metallic guy wire?

2. Tripod mount

        + Sturdy
        + Can accomodate my 6' piece of 1-5/8" steel fence post.
        - Lots of holes (and silicon caulk) in the roof.
        - Lots of climbing around in the attic.
        - Potential for a leaky roof.
        - Not asthetically pleasing to anyone but a Ham.

3. Chimney mount

        + Can get the parts at Radio Shack. Easy to install.
        - Must take it down when needed chimney repairs
          (at the very top / cap) are done.
        - Will it put too much stress on my 49 year old chimney?

4. Vent Pipe Mount

        + Easy, cheap.
        - Not sure that the vent pipe mount is strong enough for
          6' of fence post + 22.5' of R7.
        - Not sure my vent pipe (either cast iron or glavanized steel)
          is strong enough, either.

5. Eve or Side of house mount
        + Cheap
        - How do a find the studs from outside? (I have asbestos siding
          that's very brittle, so I *can't* go punching test holes with long
          thin nails into the side of the house.)
        - Would need a longer piece of mast to clear 5-8' above the roof.
        - Least asthetically pleasing.

Right now, the tripod mount seems to make the most sense since it's
the sturdiest. Any tips on mounting are welcome. One suggestion I've
received from a co-worker is to make a "sandwich": bolt the tripod
to a 2x4. The bolt then runs through the roof to a 2x6 mounted on the
other side of the rafters. So the sandwich is the 2x4+rafters+2x6.
White plumbing//hvac adhesive/sealant or silicon was recommend to
be used in copious amounts. Any other suggestions? How should I treat
the 2x4 that's on the outside?

How about any of the other methods? How else have people on qrp-l
roof mounted their verticals?

dit-dit-dit dah-dah-dah dit-dit-dit,

/eric rehm
kj7ae
Seattle, WA


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