[TowerTalk] MA-550 advice...

Mon Aug 18 09:39:20 EDT 2003

Jim - I'm now on your page after strugging with alternatives.  For my QTH,
the MA-550 seems perfect -- neighbor and code friendly in terms of
appearance and ability to lower it below the roofline of the house, easy to
install assuming I can work on its top side from the second story roof.

Sure could use your experience now that I'm running on this track.  E.g.:
Hadn't even thought of sound deadening as an issue.

Situatin: I'm assuming I'll use a MAB or MARB base.  Antenna will be a Force
12 3CSS weighing 25#, and a 2 meter yagi and 2m/0.70m vertical above it, and
some kind of nice rotor; a bottom mounted would certainly look nicer and be
a lot less hassle to maintain.  I'm in my mid-50's and in excellent shape,
but that may not always be the case in the future....  $ is an issue, of
course, but I want to make sure I'm not pennywise and # foolish.

Questions:

1.  Is is practical to use the MARB rotator base and still attach the unit
to the roof?  Is there an available bearing?
2.  If I don't attach to roof, does the 3.5' x 3.5' x 5' concrete pier still
provide sufficient stability?
3.  Raising lowering - do I need the MAF if I can use the roof structure
itself and a block and tackle?
4.  Motorizing the up and down...
      hand crank vs motor?
      buying the MD-75 or MD750 vs rigging a lower cost motor later?
      which US Tower options are worth it?
5.  Noise management

David, WA6PXX

-----Original Message-----
From: Jim Jarvis [mailto:jimjarvis at comcast.net]
Sent: Sunday, August 17, 2003 3:13 PM
To: David Giuliani
Subject: RE: [TowerTalk] rohn 25G--a third thought

Dave...

It occurs to me that if you're building the house
from scratch, you can incorporate some backing
plates in the framing, to make it easier to install
a house-mount bracket, outside the structure.  That
way, you'll save yourself some schlepping in the attic
on a hot afternoon.

Regardless of tower type, the stock brackets are not
strong enough, in my opinion.  I've built mine out
of 2x6 and 2x8, and either bolted or lag-screwed them
into house framing.  Usually, I extend over 3 roof
trusses, making it a 48" plate that attaches to the
house...and which has carriage bolts extending out to
allow a second plate to be bolted down to the one which
is house-bracketed.

In the case of Rohn, that second plate goes over the
legs and ties the tower in. This is useful where you
don't need to stand off any great distance to clear an
eave or soffit. If standoff is an issue, their brackets
are fine.

In the case of US tower, the bolts simply go through the
house-bracket which comes with the tower.  Should you go
with the telescoping tube, I have some thoughts on sound
deadening.  Won't bore you with them unless you go that way.

N2EA, Jim

-----Original Message-----
From: David Giuliani [mailto:David at Giuliani.org]
Sent: Sunday, August 17, 2003 20:07
To: Jim Jarvis
Subject: RE: [TowerTalk] rohn 25G

Thanks, Jim - very helpful.  Glad that Rohn is still in the business.   I'll
call them and check delivery.

I'm getting concerned about placing the lower half of the tower running
through the upstairs bath closet and down onto the garage floor - lighting.
I'd be well grounded (say 8 rods + ufer connection to foundation), but even
still.  I'm also thinking that the hazer elevator system would be a very
nice way to raise and lower the antenna, for only small $$ beyond the hinge
plate.

David, WA6PXX

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of Jim Jarvis
Sent: Sunday, August 17, 2003 11:13 AM
To: Towertalk
Subject: [TowerTalk] rohn 25G

Dan  (TT):

Rohn still lists 25G on its website, and will sell it
in either 10' or 7' section lengths.  The latter is UPS
shippable.  Price for 10' was $89.

I suspect what they're doing is bypassing the dealer
network, and taking the margin themselves.  Hence, the
story that Rohn isn't selling it; dealers can't get it.

As for the proposal to hinge 25G at 30'....it might make
more sense to hinge it at the base, and use the house
bracket and base as mounting points for a pulley system.

you'd want to calculate the load on your roof truss,
before embarking on the adventure, of course.

I recall seeing Rohn's catalog quoting 25 or 30' above
a house bracket as the safe unguyed height for 25g, with
a 2 sq. ft. antenna windload, in 70mph.  However, I no longer
have my Rohn commercial catalog, and am unsure.

I'd asked this question on this reflector a week or so back,
and had but one person echo my recollection.

Rohn no longer makes foldover sections for 25g or 45g...too
many failed due to amateurs overloading them.  One of those
at 30' would work nicely.  I had one in my 45G in Vermont,
for three years.  Beware, though:  they're very heavy, and
the 45g was an assembly nightmare.

There was an M.E. on here a couple weeks back, who compared
MA550 tubular strength to 12" triangular tower strength...
Sure would like to see that replayed.

n2ea

_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.

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