[TowerTalk] Alliance Rotator

[Stan Griffiths]

>Hello All,
>
>     I just picked up some Rohn 25, and it came with an Alliance HD-73-1
>"Heavy Duty" rotator mounted in the top section.  The Alliance owner's
>manual section on wind loading runs about 400 words, but I think it was
>written by the marketing department!  If there's any real info in there, I
>am unable to extract it.
>
>     Is there anyone on the list who has experience with this rotator?
>
>TNX and 73, Ken
>
>
>Ken Freedman
>AKA: N1QQV/QRP  VE, EC Madison CT, QRP-L
>Living Proof That, "You don't have to be a blonde to be light headed!"

Hi Ken,

W7WHB and I owned a radio store once.  We handled HD-73 rotators and put one
on the roof on 20 feet of Rohn 25 with a TH6 on it.  It quit rotating after
a moderate wind of perhaps 50 mph.  When we looked in side, the casting that
holds all the gears was shattered.  I think the rotator freewheeled in the
wind and crashed into a hard stop inside the rotator which broke the gear
housing.

The HD73 does have a brake, but is nothing but a disc about the size of a
quarter mounted on the motor shaft that drags against another disc when the
motor is not energized.  This is not a locking brake like the Ham-M and
later rotators of that series have.  It only increases the friction but
still allows the rotator to turn in a wind.

Alliance rated the HD73 at 10 square feet and the TH6 proved to be too much
for it even though it is less than 10 square feet.

The fix for our broken rotator was a completely new gear box.

Chapter 2:  I recently bought an estate sale in which I got a Triex W51 with
a TH6 mounted on it.  The rotator was a Ham-4 in working condition.  In the
garage, I found an HD73 and when I took it apart, guess what?  Yep.  A
broken gear box casting . . .  I still have that piece of junk and I am
wondering if I can still get a gear box for it . . . ?  If so, I will sell
it immediately.  I would not put another one up with more than a small
tribander or a small VHF array on it.

That is my total HD73 experience.  Oh, yes.  We did sell about 20 of them to
customers and never had a complaint from any of them . . . I wonder why?

Stan  w7ni@teleport.com


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