RE: K60XV with KAT2 ALC problem

Posted by Don Wilhelm-3 on Mar 06, 2005; 11:23pm
URL: http://elecraft.85.s1.nabble.com/K60XV-with-KAT2-ALC-problem-tp375428p375429.html

Greg,

Take a look at the K60XV errata sheet, and look for the 470 ohm resistor
that is supplied with the K60XV - that resistor is to replace R6 on the KAT2
board.

The problem is that all options that drive the VFRDET line except the KAT2
use tri-state drivers, but it would be difficult to change the KAT2 to a
tri-state driver - so the KAT2 output interferes with the K60XV output
signal when the K60XV is active.  The increased value resistor almost
eliminates the interaction and does not hurt the KAT2 when it is used.

73,
Don W3FPR

> -----Original Message-----
>
> With the tuner plugged in, the ALC voltage, on pin 6 of J13 on the
> K60XV, varies from 0.820V at minimum power to 2.971V (Fluke 8060A with
> current calibration sticker, all the digits are correct) when it stops
> going up, at .70 mW indicated, it looses ALC control.
>
> With the tuner unplugged, it seems happy, ALC runs from 0.811 to 3.505V
> when it's claiming to be making 1 mW (it really only makes 0.820 mW but
> I can live with 0.8 dB low. I'll work on calibration later).
>
> I looked at the tuner, R6 (47 ohms) is present and correct. R6
> "isolates" the ALC buss from the low output impedance of the LM358 that
> makes the forward power indication on the buss.
>

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