(this is a constantly evolving work in progress of my optimal setup for my K3 - current info at top of page, archived info further down)
Receiver
AGC and Headphone volume I use a Heil ProSet for ssb and Sennheiser HD280 for cw. See AGC/Gain setting page for proper setting of AGC and RF/IF Gain. I always try to maximize rx dynamic range. I normally leave AGC SLP at 0, AGC THR at 8, ATT ON, RF Gain at 2 o'clock, and AF Gain between 9 and 12 o'clock. With these settings, AGC Threshold has been raised to s9 and an increase in signal level from s3 to s9 causes a 30dB increase in audio level. When I'm running in contests (i.e., calling CQ), I turn off AGC (with AF Gain increased to 3 o'clock and CONFIG AF LIM at 22) to maximize pileup readability and minimize effect of neighboring key clicks 2011 Audio Updates - DSP and IO Boards In Jan 2011, I updated my KDSP3 and KIO3 boards - these boards have been improved by Elecraft since I purchased my K3. Improvements include component changes yielding better low end extension on receive and transmit as well as lower distortion.

K3 SSB Receive Passband: magenta is before updates, yellow is after updates (both with shift at FC=1.45Khz and flat RX EQ)




K3 SSB Receive Passband with RX EQ - almost ruler flat 40hz - 3000hz, slight roll off to 3400hz and then steep roll off



The updated RX and TX EQ settings are as follows:
MenuFunctionRX EQ
(SSB)
TX EQ
ESSB
EQ 150hz+3+16
EQ 2100hz+3+16
EQ 3200hz+2+2
EQ 4400hz0+1
EQ 5800hz+10
EQ 61600hz+10
EQ 72400hz+10
EQ 83200hz-1+1

Width Setting (SSB) The K3 receiver in ssb actually has a bandwidth about 100hz narrower than indicated on the display. For example, 1.9Khz on the K3 is equivalent to 1.8Khz on other radios. Shift Setting (SSB) The Shift (center freq) value has to be shifted downward as you narrow the ssb selectivity to preserve good intelligibility. These values work well for me:
WidthShift
2800CF=1.45Khz
1900CF=1.15Khz
1700CF=1.05Khz
1500CF=0.95Khz
For contesting, I use width 1600hz, CF=0.95Khz

AF Limiter An AF level limiter was introduced with firmware version 2.65 for use with AGC off. I have it set to "22" and use it often. It is amazing how quiet and natural the receiver sounds with RF Gain reduced and AGC off. See AGC/Gain setting page for proper setting of AGC and RF/IF Gain VFO Tuning Rate VFO FST is set to 20 to make the fast tuning rate more useable CW: 1Khz/rev slow, 2Khz/rev fast: VFO CTS=100 VFO FST=20 VFO CRS=1.0 SSB: 2Khz/rev slow, 4Khz/rev fast: VFO CTS=200 VFO FST=20 VFO CRS=5.0 Transmitter
TX EQ Settings See table above - these settings were determined by recording my actual transmit signal on a second receiver with a 6Khz passband. For contesting and dx'ing, I use flat RX and TX EQ (non-ESSB).

K3 ESSB Transmit Passband: magenta is before dsp updates (400hz low), green is after updates without EQ (200hz low),
yellow is after updates with EQ (100hz low)       (the 60hz peak is a computer artifact and is inaudible)

Mic Gain and Compression To correctly adjust Mic Gain, turn compression off (CMP=0) and slowly increase MIC while speaking a steady "aaaaahhhhhh" - you want to reach the 5th bar of ALC and not have the 6th bar turn on. After this is set, don't touch MIC. I found that for ragchewing, I want compression off for smoothest audio. For contesting, I set CMP to 23. Archived Info
(this info stems from earlier versions of firmware and before the 2011 DSP/IO updates, but almost all of it is still relevant) EQ Settings - Rag Chewing Below is the receive audio passband spectra at 2.8Khz and 3.2Khz width using the 2.8Khz and 6.0Khz 8-pole filters. With the lowend extension added in firmware version 3.33, the receive passband is now flat down to 100hz with the RX EQ shown. For SSB, the Shift control was adjusted for FC=1.35, which is the maximum shift toward the low frequency that has any true audible effect. For AM, the Shift control is set to FC=1.65
MenuFunctionRX EQ
(SSB)
RX EQ
(AM)
TX EQ
(Ragchewing Heil HC5)
TX EQ
(Ragchewing Pro audio line in)
TX EQ
ESSB
EQ 150hz+90000
EQ 2100hz+5+8/+400+16
EQ 3200hz+20+5+2+6
EQ 4400hz00+20+3
EQ 5800hz+10-50+1
EQ 61600hz00-800
EQ 72400hz-10-80-1
EQ 83200hz-1+1-200

Elecraft K3 SSB Receive Passband: yellow is 2.8Khz filter, aqua is 6.0Khz filter at 3.2Khz width (both with shift at FC=1.45Khz)
(the 60hz peak is a computer artifact and is inaudible)


New lowend K3 Receive Passband extension with version 3.33 (and later) firmware, with EQ as shown above

TX "Pro" audio setup:
  • Marshall MXL2003 condensor mic
  • Behringer VX2000 voice processor with expander off, Voice Optimized EQ +4dB Presence
  • Behringer PEQ2200 parametric EQ (210hz 2.5oct -15dB, 450hz .55oct -9dB)
    For contesting, RX EQ is flat.

    TX ESSB Elecraft provides support for 3.0-4.0Khz transmit bandwidth via dsp filtering starting with firmware version 2.23. Below is a plot of the measured transmit passband bandwidth with the K3 configured for 2.8Khz (aqua, non-ESSB), 3.0Khz (yellow, ESSB) and 4.0Khz (green, ESSB) transmission. No TX compression was used.

    TX EQ Off: Elecraft K3 SSB Transmit Passband at 2.8Khz (aqua), 3.0Khz (yellow, ESSB) and 4.0Khz (green, ESSB)



    TX EQ On: Elecraft K3 SSB Transmit Passband at 3.0Khz (yellow, ESSB) and 4.0Khz (green, ESSB)



    RX EQ Settings - Pink Noise Rolloff Paul PD0PSB suggested a pink noise 3dB/octave rolloff in the rx audio spectrum would create smoother sound in a posting to the Elecraft reflector. I tested the suggestion using various RX EQ settings to vary the onset and degree of the rolloff as follows:
    Menu Function RX EQ
    (200hz)
    RX EQ
    (350hz)
    RX EQ
    (500hz)
    RX EQ
    (1000hz)
    RX EQ* (rev D KDSP3)
    (1000hz)
    EQ 150hz+9+9+9+9+2
    EQ 2100hz+5+5+5+5+1
    EQ 3200hz+2+2+2+2+1
    EQ 4400hz-3-100-1
    EQ 5800hz-5-4-3-10
    EQ 61600hz-10-8-5-3-2
    EQ 72400hz-16-10-7-5-4
    EQ 83200hz-16-16-10-10-8

    To my ears, the 1000hz rolloff (last column above - yellow curve below) sounded best. Here are the resulting audio spectra:

    Elecraft K3 SSB Receive Passband with RX EQ settings shown immediately above. Red is flat passband, Yellow is 1000hz rolloff, Green is 500hz rolloff,
    Magenta is 350hz rolloff, and Aqua is 200hz rolloff. K3 is in USB mode with 6.0Khz roofing filter at 3.2Khz width FC=1.45Khz

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