[Elecraft] KX3 beta firmware rev 1.61: SSB, ESSB, and AM improvements, etc.

[Wayne Burdick]

KX3 beta firmware rev 1.61 (with DSP rev 1.23) is now available. See release notes below.

You'll need the KX3 Utility application to download and install firmware. For full instructions on loading beta releases, refer to our KX3 software page:

http://www.elecraft.com/KX3/KX3_software.htm

73,

Wayne
N6KR

* * *

MCU 1.61 / DSP 1.23, 8-31-2013

* AM TRANSMIT IMPROVED: Depth of modulation increased.

* SSB SPEECH COMPRESSION IMPROVED: Significant cleanup of opposite-sideband intermodulation (IMD) products with speech compression turned on.

* ESSB MODE IMPROVED: Speech compression is now automatically disabled when ESSB mode is turned on. This completes the ESSB implementation. To turn on ESSB, use the TX ESSB menu entry. Tap ‘1’ to turn ESSB on/off; use VFO A to adjust the transmit bandwidth from 3.0 to 4.0 kHz. (These menu changes cannot be made while in transmit mode.)
 
* ROOFING FILTER USE CONFIGURABLE IN SSB MODE: Roofing filter FL2 (3 kHz) can now be inserted when the upper edge of the receive passband is either 2.4 kHz (original value) or 2.9 kHz. When the passband edge is higher than this point, FL1 is used (wide filter). If the KXFL3 filter option is not installed, FL1 is always used.

If you frequently encounter QRM in SSB modes, use the 2.9 kHz selection; this will insert FL2 when normal passband settings are used. If QRM is less of an issue or you frequently use ESSB, use the 2.4 kHz selection (original value); this will insert FL1 for normal passband settings. The PBT knob can override either selection (see below).

To select the desired FL2 insertion point: Locate the PBT SSB menu entry. Tap ‘1’ to select either 2.4 or 2.9 kHz using the criteria above.

Impact of FL2 configuration on the NORM function:  If 2.4 kHz is selected, NORMalizing the passband (by holding the PBT knob) will select FL1 (wide filter). If 2.9 kHz is selected, NORM selects FL2 (narrow). Impact of FL2 configuration on the PBT I/II functions:  When LO-HI CUT is in effect for SSB, the FL2 setting determines when FL2 is inserted as HI CUT (PBT II) is adjusted (2.4 or 2.9 kHz). When WIDTH / SHIFT (NOR) is in effect, the FL2 setting affects both adjustments. For example, with the passband NORMalized, reducing WIDTH (PBT I) inserts FL2 at either 1.7 kHz or 2.8 kHz, for the 2.4 and 2.9 kHz FL2-insert selections, respectively. However, the insertion point for FL2 is also affected by the SHIFT setting (PBT II).

Note on SSB demodulation methods used for FL1 vs. FL2:  When FL1 is in selected (wide filter), the KX3 uses conventional SSB demodulation, providing the best overall audio fidelity. When FL2 is selected (3 kHz filter), the KX3 uses “Weaver” SSB demodulation, which introduces a narrow 1.5 kHz notch into the receive passband as part of the DSP algorithm. This notch typically has no impact on speech intelligibility, but it can sound slightly different to an operator who is most concerned about fidelity.
  
* CURRENT DRAIN LIMITS ADJUSTED: Receive and transmit current drain limits were set a bit too low, occasionally causing an unexpected roll-back of power output or turn-off of the KX3. Note: If rollback of power output still occurs, it is probably because the supply voltage is dipping below 11 V on keydown, or because of excessive transmit current drain, possibly due to a low-impedance load.