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Re: Lifetime of Azimuth/elevation setups in winter.



Patrick:
I've had a full- blown, full auto az-el setup, in VA -- which is milder 
than where I am now (PA), but still, saw ice and snow.

I never had weather issues.

I did have design issues:  The Yaesu G5400 is GROSSLY underdesigned.  My 
first indication of this was when the elevation motor seized, taking out 
the power transformer, FOLLOWED by the fuse.  Later, I had ANOTHER 
elevation motor failure, despite ENSURING that there was no unbalanced 
torque.  This time damage was limited to the motor.

Recommendations:
1.  Make SURE that your entire array is balanced such that the elevation 
rotor is not trying to lift a bunch of weight, merely overcoming inertia 
(which is plenty if you have a 2m cross yagi).
2.  Replace the fuse that comes with your rotor with the lowest value 
slow-blow which will not fail under starting load.  This is how I 
prevented further cascading failures.
3.  If you run any kind of automatic control (recommended) make SURE 
that it has decent stall detection/protection.  If it issues a move 
command and doesn't see motion in some number of seconds, it should turn 
off all motors, inform you, and do nothing else until manually reset.  
Not all products meet this test, I'm told.  Full disclosure:  My 
software was homebrew, and I'd implemented what I thought was rigorous 
stall detection, but obviously not.  Turns out that there were some 
subtlties with using multiple interrupts in DOS that I didn't initially 
understand, so insufficient testing did not disclose that my software 
was not doing all that I wanted.  After the first failure, I did some 
more rigorous testing and sorted it all out.
4.  If you run automatic control under MS Windows, be careful.  I'm told 
that if Windows has an error (Critical stop??) which presents you a 
message you need to respond to (like an attempt to write to an empty 
floppy drive) EVERYTHING, including background tasks stops until you hit 
"OK".  (I've NOT tested this, and behavior may be improved with newer, 
more preemptive versions of the OS, but I'd verify before trusting.)  
External devices, like Steve Bible's Easy Track may get commands from 
Windows tracking S/W, but do not care what windows does if they detect a 
stall -- they respond appropriately.  For this reason, I now prefer Easy 
Track to my homebrew hardware/software, except under DOS (which works 
just fine to track and work 9K6 baud birds.)

Design notes:  The G5400 has no thermal protection for the elevation 
rotor, only limit switches at the extremes of elevation -- which are 
absolutely useless if a tree grows into the arc of your 2m longboom 
antenna..  The Azimuth motor DOES have a thermal trip inside it, tho 
it's held to the motor windings with a cheap piece of tape, which dries 
out and separates, leaving the sensor hanging in the air -- which I 
discovered when I had to repair the position sensor pot because the 
cheap tape failed, allowing the fine wire to the slider to break due to 
fatigue failure.  I repaired with good tape backed up by a UV ty-wrap.  
This is why, despite trees, I never had to replace the Az motor.

I'm TOLD (no first-hand experience) that the G5500 has no thermal 
overloads, only limit switches.  It appears to be a bit more rugged 
mechanically, so there's hope if you implement the recommendations above 
regarding stall protection and fusing.

Again, I had NO problems, despite Ice storms and snow.  The above passed 
on for lessons learned/knowledge sharing.

Hope this helps, happy to answer questions.

Good luck and very 73,
Jim
wb4gcs@amsat.org


Patrick Green wrote:

>Hi All,
>
>  I'm considering setting up a full blown satellite setup and am
>concerned with the effects of WX on the fragile setups of AZ/EL rotor
>setups.  I want to hear about people that have had horror stories and
>ones that "set it up once" and never had issues with it for years. 
>I'm in the Chicago area and we do freeze and get all the nasty winter
>weather.
>
>I've always been a "portable" setup person and you might see me
>operation the next HEO with something I can setup and tear down in an
>instant.  I've always liked this because when I travel, I can access
>the same quality setup where ever I go.
>
>73 de Pat --- KA9SCF
>----
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