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From: Eric Gustafson[SMTP:n7cl@sparx.mmsi.com]
Sent: Monday, August 10, 1998 11:41 AM
To: AF7Y@msn.com; towertalk@contesting.com
Subject: Re: [TowerTalk] Parts for AEA Isoloop
Hello Eric:
I think that what you have noted is accurate in the statement of the symptom,
but not necessarily the cause. It turns out that there was a production flaw
in the early IsoLoop antennas that caused the parts to stress and break out.
It was caused by driving some shear pins through the gear into the fork
assembly. With time, the fork assembly simply cracked and would no longer
support the gear. AEA simply started drilling the holes that the shear pins
went into and apparently fixed the problem altogether.
Tempo Research, the new parent company, is offering a repair kit composed of a
new gear, the fork and pins for $20.00 which I believe includes shipping and
handling. You can order one by calling 1-800-258-7805 and asking for Annette.
If you find a source for this part, please post it here on the
reflector. I have been involved in troubleshooting problems with
5 of these loops now here in the Tucson area. All of the
problems were ultimately traced to a failure of the part you
describe. Fortunately, this all happened while we could still
get replacements from AEA.
This part is obviously underdesigned for its intended
application. Of the 5 loops we repaired here, 2 failed to
survive shipping. They didn't work when tested on the ground
right out of the box. One more didn't survive installation
(worked on the ground but not once up in the air). The other two
failed during relocation. We are pretty sure that these loops
were bumped from the side during handling as a part of the
relocation process. We know for sure that one of them was
temporarily placed on the roof in the vertical orientation. The
owner lost his hold of the top of it and it tipped over about 12
inches until it hit the chimney that it was next to. This was
not a tremendous shock. But it was in exactly the wrong plane
for stressing this part.
Anyone owning one of these antennas:
Be EXTREMELY careful to prevent shocks from being delivered to
the loop case from a direction perpendicular to the plane of the
loop. In fact, handle the thing like it was an expensive piece
of crystal or china. The plastic coupling that connects the
stepper motor to the capacitor rotor (a fairly massive assembly)
is the only source of mechanical support for the motor end of the
rotor. This piece of plastic is not designed to be able to
withstand the loads it is exposed to when the antenna is
subjected to any sudden acceleration. Even normal shipping and
handling stresses are sufficient to cause failure of this part.
The first sign of failure (prior to complete failure) is
excessive (and increasing) backlash in the tuning mechanism.
73, Eric N7CL
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