Elecraft K3S
firmware v2.23
Elecraft · Released Jul 31, 2008 · First seen Sep 14, 2026
Source:
elecraft.com
v2.23 is not the latest firmware for the Elecraft K3S: the current version is v5.67 (January 22, 2019). Go to v5.67
In short — summary by updatemystuff.com
ESSB transmit added for wider SSB bandwidth, LSB/USB equalization improved.
- ESSB transmission added, supporting up to 4 kHz bandwidth
- LSB/USB transmit equalization improved to fix gain imbalance
Written from Elecraft's release notes, which are printed in full below.
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What's in this update
- LSB/USB TRANSMIT EQUALIZATION (experimental): Improved gain balance between LSB and USB. A 1 to 3 dB difference between the two had been reported with the 2.7 kHz (5-pole) filter. The passband should also be slightly flatter.
- ESSB (EXTENDED SINGLE SIDEBAND) ADDED:~ Allows the K3 to transmit in SSB modes at a bandwidth of up to about 4 kHz. Requires a 6 kHz crystal filter on the RF board. Note: ESSB receive is obtained just by adjusting the WIDTH control.
To enable ESSB transmit: (1) Make sure the 6 kHz filter is configured correctly for AM transmit; switch to AM mode, then specify this filter using CONFIG: FLTX AM. (A future firmware release should allow use of the FM filter for SSB as well, pending lab tests.) (2) Locate CONFIG: TX ESSB.
Select the desired extended bandwidth for SSB transmit (3.0 to 4.0 kHz) using VFO A.
Then tap 1 on the keypad to turn ESSB on/off.
When on, the Ò+Ó icon in the mode area will turn on. (If you turn ESSB on/off frequently, you might want to assign the TX ESSB menu entry to a programmable function switch.)
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