Hi Mark, WA8SME
Sometime the voltage regulators tends to self-oscillate in a very low but very wide frequency band.
In this condition the regulated voltage is unstable not clean and dirty as can be seen using an oscilloscope.
This problem is well know by the microwave people when they try to get a local oscillator clean and stable.
To eliminate the self-oscillation an effective cure is to put a ceramic capacitor of 0.1 uF in parallel to an electrolitic capacitor ranging from 1 to 10 uF both at the input and the output of the regulator and check again with the oscilloscope any trace of oscillations at the regulator output.
73" de
i8CVS Domenico
----- Original Message ----- From: "Mark Spencer" [email protected] To: [email protected] Sent: Monday, July 13, 2009 8:42 PM Subject: [amsat-bb] G5500 Rotor Drift Issue
There have been a couple of recent posts about a G5500 voltage drift issue and some solutions. I'd like to thank those gentlemen for the posts and
the
solutions. I am in a unique position to be able to work with nine G5500 rotors side-by-side in preparation for the Teachers Institute II that I
will
hold at the end of the week. I noticed the same warm-up/calibration issue mentioned in the posts. I discovered that it took on average 10 minutes
of
warm up time for the voltage to stabilize, and this voltage is the
reference
on which the antenna position indications are based. The difference
between
the cold start and warm up position was around 10 degrees for AZ and 4 degrees for EL. Minor but irritating. I thought I'd try the easiest solution suggested first (changing the output cap on the regulator to
.1uF)
before I tried the more dramatic solution of changing out the voltage regulator. I simply tack soldered the .1uF cap on the exposed leads of
the
existing .01uF cap, and it worked like a charm. All nine rotor
controllers
fire up at 6.12 volts and hold that voltage throughout the operation of
the
rotor. This sure will make instruction of rotor setup and calibration a heck of a lot easier. Thanks for the suggests.
Mark Spencer, WA8SME
ARRL-The national association for Amateur Radio
Education and Technology Program Coordinator
http://www.arrl.org/FandES/tbp/
530-495-9150
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb