[Elecraft] K3 FIRMWARE UPDATE: MCU 1.87, DSP 1.69 (Finally!)

[Joe Subich, W4TV]

> MCU 1.87 / DSP 1.69, 5-3-08

>    * AM RECEIVE WIDTH RANGE INCREASED:  The WIDTH control in AM 
> mode now has a range of 2.8 to 10.0 kHz. Wider settings provide 
> outstanding fidelity for hi-fi speech and other wide-band signals. 
> This is the *IF* filter bandwidth -- the traditional way to show
> bandwidth for AM, because the required IF bandwidth is twice the 
> modulation bandwidth. 
>    NORM selects an IF bandwidth of 6.0 kHz in this mode. WIDTH 
> settings above 6.0 kHz will not be useful unless you have an FM-
> bandwidth crystal filter installed (at FL1).

Audio response is limited to 4.2 KHz with either the FM filter (13 
KHz) or AM filter (6 KHz) at FL1.  With the AM filter, 4.2 KHz is 
wider than necessary.  With the FM filter, the 4.2 KHz high cut is 
less than the 10 KHZ of IF bandwidth.  Why is the IF bandwidth and 
audio response excessively restricted with the FM filter?  It should 
be possible to achieve at least 12 KHz of IF bandwidth and 6 KHz or 
more of audio bandwidth depending on the filter skirts. 

>  * IF A 2.8 KHZ FILTER IS INSTALLED, SSB "NORM" BW is 2.8 kHz 
> (was fixed at 2.7 kHz).

Can this be extended to CW and Data?  It appears that "NORM" is 
currently fixed at 400 Hz regardless of mode and filter.  500 Hz 
would be more appropriate for CW with the 500 Hz crystal filter 
and even wider values might be appropriate for some DATA A modes 
with a 1000 Hz or 1.8 KHz filter. 

>    * AUTO-SPOT (SPOT with CWT ON) now works with both very 
> weak and very strong signals.

Auto-spot consistently tunes to a tone 50 Hz low (50 Hz below 
the value set for pitch). 

>    * SSB TRANSMIT BANDPASS EXTENDED AT LOW END. Improvement 
> is about 2 dB at 300 Hz, 3 dB at 200 Hz, and 6 dB at 100 Hz. 

Can this be made optional?  Excess LF response only wastes 
power at low frequencies and occupies excess bandwidth. 

> Additional improvement possible via TX EQ.

Will TX EQ be made mode and/or input dependent?  Setting TX EQ 
for voice screws up the audio response for digital mode (AFSK A 
and DATA A) operation.  The same is true for RX EQ. 

73, 

   ... Joe, W4TV