[Elecraft] Re: KX1 debug questions

[Wayne Burdick]

Robert Greenwalt wrote:

> I just completed the KX1 kit and I've got a couple issues.  I was
> wondering if anyone else noticed them (are they normal, or is there a
> problem..):
> 
> First, the 3 digit LED emits some light at strange times.  This unwanted
> lighting is very very dim (verge of detection), or I wouldn't have a
> doubt something was wrong.  

Hi Robert,

Another good catch! We should make you a field tester next time  ;)

Some LED segments may continue to be very (very!) weakly illuminated even when
the LED is in its off state. The reason for this is that the MCU does periodic
checks for switch inputs, encoder movement, supply voltage, etc., using the same
I/O lines that are involved in multiplexing the display. Even though the duty
cycle of these background checks is very small, the LEDs are incredibly
efficient: they'll glow a little bit even with average currents in the tens of
microamps. In fact the LEDs are so efficient that the entire 3-digit display
draws only an average of about 1 milliamp--total!--with the LED value set to "2"
(about right for use in indoor lighting). 

So this is nothing to worry about. Again, I'll add a note to the manual.

> I've also noticed that when changing values on some menu items
> where the value changed for every 2 position changes on the vfo knob
> (low bat setting, for example) the left-most digit would light and turn
> off alternatively with every position change on the knob.

This I did not notice during testing. I'll take another look at it. I'm sure
it's of no consequence in any case.


> My second issue is headset noise during menu ops/display changes.
> Without an antenna and with the af gain turned up I hear noise through
> the headset during menu operations.  Is that normal?

Yes. When you press a switch, it sets off a mad scramble, with some 10
interleaved firmware "state machines" doing their thing, looking for further
input, debouncing the switch, in some cases generating tones, running timers,
etc. This burst of MCU activity injects a small amount of noise into the
sidetone outputs, mute line, etc., and it can be heard with no antenna.

Workaround: use an antenna  ;)

73,
Wayne
N6KR


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