Topband: Key Clicks

[Tom Rauch]

> Next, I raised the drive level to 80% of the ALC range 
> (Drive control at
> about 1:00)
>
> Icom Setting                Measured
>
> 2 ms                            0.2 ms
> 4 ms                            0.5 ms
> 6 ms                            1.1 ms
> 8 ms                            1.5 ms
>
> ALC has a profound effect on the IC-7800's CW rise/fall 
> time and indeed, on
> most radios.

ALC is part of the power control loop, and is not adjustable 
in rigs without a "drive" control.

In the FT1000MP series you can go into a menu and change the 
drive setting. I have details on the MKV at

http://www.w8ji.com/ft1000mk_v.htm

I have a question Paul. What ALC level does ICOM say to run 
on CW? Do they tell you to barely run the ALC up with the 
drive control?

73 Tom


> About eight years ago, I ended up modifying a Ten Tec Omni 
> Six after the
> factory "Plus" upgrade.  Once distinct difference after 
> the upgrade was that
> in an attempt to control a very slight amount of power 
> overshoot in the
> original Omni Six, the Plus' ALC was redesigned by the 
> factory to completely
> eliminate the power spike.  In doing so, the leading-edge 
> rise time was half
> of what it was on the original Omni Six.  No amount of 
> adjusting of the
> internal rise/fall control had much of an effect on the 
> leading waveform
> edge.  Later Omni Six Plus units eliminated the control 
> altogether and fixed
> resistors were used.  (i.e., why have a control if it no 
> longer works as
> designed?)  Take a look at the QST product reviews for a 
> comparison between
> the keyed waveform of the Six and Six Plus models.  I 
> ended up re-designing
> my Plus with a 2-speed ALC circuit that held power spikes, 
> yet left the
> ramped waveform intact.
>
> For the measurements above,  I am using a microHam CW 
> keyer modified with an
> isolated open-collector to +Vcc through a 1K limiting 
> resistor for
> triggering an 80 MHz Tektronix SC 504 dual-trace scope. 
> This allows me to
> take reasonably accurate measurements without having to 
> chase the waveform
> on the screen by changing the time base.  My measured 
> points are taken at
> the point where the keyed waveform starts taking off and 
> ending where full
> output is reached.
>
> Paul, W9AC
>
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