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Re: Yaesu G500 bearings, KLM antennas

----- Original Message -----
From: "KYLE YOKSH" <yokshs@sbcglobal.net>
To: <amsat-bb@amsat.org>
Sent: Friday, March 21, 2008 8:36 PM
Subject: [amsat-bb] Yaesu G500 bearings, KLM antennas

> Hello,
>   I've got a KR-500 and G500a rotor that need a good servicing. I've found
> a lot of great info in the archives that will help me, but still have a
> questions..
>   I've read that the original bearings were steel, and begin to rust
> almost immediately after installation.  Can anyone suggest a better
> bearing, and perhaps a source and part number?
Hi Kyle, K0KN

The KR-500 and G500a elevation rotors are mechanically similar and if
you look at the KR-500 Instruction Manual you will find the exploded
mechanical drawing with part numbar and location.

Each bearing is composed by part numbar 34 made with 20 ball bearings
size 0.312 ( 5/16 inch ) and a bearing holder part number 33

By the way  one groove for the balls is casted into the "aluminum boom
shaft tube" part number 29 and the other groove is casted into the rotor
housing 1.2.

The bearing holder 33 is a stainless steel toothed ring with 20 teeth and
the purpose of it is to keep the 20 balls separated each other while holding
the lubricant grease between them and lubricate the grooves during rotation
preventing in addition the wather to enter the rotor housing from the

The problem here is that the balls are not in contact-to-contact each other
but they are separated each other by the teeth of the bearing holder.

In this condition when the weight of the antennas is very large the radial
vertical force generated by it's weight is not absorbed by the balls but  is
completely applied over the teeth and so the 20 balls will be forced to
separate away one from the other.

This load is responsible to wear out, to deform and to cut the teeth but
as soon only one or two teeth are broken then the distance from the balls
decreases so that the assembly tube gear 31 has room to fall down a little
bit but the distance between it and the internal gear 10,11 increases up to
a point that to come into gear with the pinion fail.
>   I've also read that the bearing cages are subject to failure, and some
>   folks prefer to ditch them altogether.
To cure this problem and prevent damages to pinion and gear 31 I have not
used anymore the bearing holder 33 but I have filled the grooves with
black molibden grease adding in it , I do not remember exacly if two or tree
more same size balls in order to replace the original room occuped by
the teeth and this rotator is actually running without problems from several
years now.

When I did this modifications in 1992 the spare parts for Kempro were sold
by SMC South Midlands Communications l.t.d in UK actually available at
shaun.hey@smc-comms.com  but I got advice that actually they do not have
many spare parts at stock for it.
>   I'm also curious if anyone has any suggestions to optimize my old KLM
>  crossed yagis?
>   I use a KLM 2m14c and 43518c, and they seem to work fairly well, but are
>  not exactly
>   top performers. I've never opened the polarization switcher units on
>  either antenna, but suppose I might want to clean the relay contacts?
I have the same antennas and for the KLM 2M-14C  I realized immediately
that the PCB of the CS3 switcher carrying the polarization relay was the
critical point exposed to rain and umidity condensation.

For the above reason I have incapsulated the PCB with it's relay into an
additional plastic box drilling  in it few suitable holes to drain out water
and let the relay to stay at the same atmospheric pressure inside and
outside the additional box and this prevent condensation of the umidity.

In order to prevent that during temperature variation occurring from night
and day new contaminated air enters inside the original relay cup ( the
relay breathe air + pollution) the original plastic cup of the switching
relay must be very well silicon sealed and the studs fitted inside the PCB
must be inspected for good soldering.

In my antenna circularity switcher CS3 I found as new that one stud was not
perfectly soldered to the trace of the PCB  but when I attemped to better
solder it I realized that the stud becames immediately oxidated when heated
by the soldering iron.
The stud of this relay is not made of copper and it became oxidated if the
temperature of  the soldering iron is too high so that it was necessary to
scratch  it and solder it again at a lower temperature using Alpha Metals
Inc. Plastic Rosin Solder 62 Sn , 36 Pb and 2 Ag

 Another precaution to increase the relay contact life is not to switch the
polarization while transmitting expecially with high power and the use
of an electrical interlock between TX and polarization Switch seems to
be a good idea.

About my 435-40CX the original CS-2 switcher is identical to that of your
435-18 C but I have not used the CS-2  because I have replace it with one
of my own designe 4 polarizations V-H-RHCP-LHCP as published into the
AMSAT-Journal, March.April 2007 Part-1 and May-June 2007 Part-2

>   Since my tower must be tilted over to service the rotator and antennas,
> I'd like to get several years of service out of this gear.
If you mount the antennas as per the Assembly Instruction of the Manual
they will be already optimized for the best performance for gain and VSWR
and I don't think it will be possible to do better.

By the way in two separate email I will send to you copy of the mechanical
drawings for the KR-500 and a set of pictures showing how I have
water-protected the CS3 for the KLM 2M-14C and as well for the KLM

>   Thank you for any help.
>   73,
>   Kyle
>   K0KN

You welcome and 73" de

i8CVS Domenico

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