[AMPS] RE: ALC

[Steve Thompson]

>Message text written by "Steve Thompson"
>
>>And FT990 and .. and...In practice, it's likely that the menu power
>setting simply sets a reference level in the ALC system so you retain all
>of the dynamic problems.<
>
>Is the FT-990 a known offender? Mine doesn't seem to generate anything
>untoward when set for about 45-50W output, and drives an 87A very happily
>with no aggro. Maybe I need a better scope <g>.
>
>73 John
>GW4FRX


Mine certainly offends with a nasty little overshoot of a few 100 us on
rising edges whenever there is any ALC action. It depends on the excess gain
in the transmit chain and varies with power and frequency. When wound down
to drive a transverter, it makes the rig too dirty to use in our contest
station with spitching covering about 30kHz. Over 24 hours, the gain varies
somewhat and it's asking for trouble to have all the ops keep tweaking the
mic gain.

The problem is that the ALC loop response is crudely slowed with a
capacitor, presumeably to keep it stable. One day I'll find some spare time
to try and improve it.

Steve



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