[TowerTalk] MARB-550

[JC Smith]

Hi Alan,

Sorry I didn’t get back to you sooner; I’ve been having problems getting my
TT messages lately (I’m on Comcast).

I have a MA-550MDP with the MARB and it’s a great little tower.  It came
(used) with a fairly beefy old HyGain Rotor (Roto-Brake 400) but I wanted a
computer controlled AZ/EL system for satellite antennas so I thought I’d
give the Yaesu G5400 a try.  In addition to the large KLM satellite
antennas, which were mounted on a crossboom through the EL rotor at the top
of the lower tower section (the one that doesn’t go up and down) I also
installed a 3L tribander (HyGain TH-3) on a 10’ mast at the top.  I knew the
AZ rotor of the G5400 set was pretty anemic so I purchased a second one,
still in the unopened box, for half price at a swapmeet as a spare.  I
figured if I had to get them rebuilt every few years, that would still be
cheaper than some exotic setup like the M^2 EME rotors.  To make a long
story short, the first one is still in the tower after almost 15 years, and
the spare is still in the box.  The TB built into the tower does a great job
of handling that big, rotating mast.  You can turn it by hand, no problem.
The big issue is the break.  The G5400 is only rated at 145 ft-lbs of
braking torque (44 ft-lbs rotation torque) but it’s been working.  I had my
mast slip inside the top tower section once, but the rotor has always held.
The weight, of course, is no factor as it is all supported by the TB.  I
should ad that we are not in a high-wind area.


I’m not encouraging you to undersize your rotor, but given the way it will
be mounted in the MARB, you don’t need to oversize it either.  The braking
torque will be your main limiting factor.

73 – JC, K0HPS