Re: [Repeater-Builder] SS-32/5K/Micor

30 Aug 2004 11:30:32 -0000

Thanks for your thoughts Bob. I have managed to minimize the problem by doing as you suggested - I put a .1 uF cap and a 27K resistor is series with the tone output of the SS-32. The frequency still drifts when the tone is keyed and unkeyed, but now only about 50-60 Hz. I think that this is acceptable. 73,

Kevin, K9HX

At 10:16 PM 8/29/2004 -0400, you wrote:
Hi Kevin,
 
I am installing a Comm Spec SS-32 encoder in a Micor
repeater. I am using a logic output from an S-Com 5K
controller to key the ground connection to the encoder
whenever the RX COR is active. I need to do this to
be able to link into another system.

My problem is when ever the encoder is keyed or
unkeyed, it causes the TX to drift off frequency about
+/- 900Hz. It apears that this is being casued by a cap
charging/discharging. I have tried several different
tone insertion points, always with the same result.

 
I haven't seen many responses, so I'll toss out some suggestions.
 
There is probably a DC bias on the Micor side of the audio connection. The SS-32 has a 1 uF polarized cap in series with the tone output with its "+" side toward the SS-32. When the SS-32 has its ground connection floating, the cap probably sees 12V on the SS-32 side and some other (lower) voltage on the Micor side. When the SS-32 is operating, the voltage on the SS-32 side of the cap may be lower than the Micor side. If the cap operates reversed biased, it can leak or short, causing wierd problems. You could try a 1 uF nonpolarized cap in series with the tone lead to see if that's the case.
 
If that wasn't the problem, and if you have plenty of CTCSS level coming from the SS-32 and can afford to lose some, use a smaller nonpolarized cap (say, 0.1 uF) in series. The lower value will attenuate the level, but may also reduce the drift effect you're seeing.
 
73,
Bob, WA9FBO







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