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Chapter 4

Chapter 4   K3 Operating Hints and Kinks

4.1    Reducing Interference with Filtering

There are three sets of filters operating in the K3. The bandpass filter operates in the receiver front-end and one of them is selected for each of the ham bands. You cannot change this filter. The roofing filter in the first IF is your first adjustable line of defense against QRM. These filters have very steep cutoff characteristics and give the K3 its reputation of being able to receive close to other stations. If you have more than one roofing filter, as most of us do, turning the WIDTH knob causes the DSP to automatically select the one that is wider than the DSP filter width. . . .The DSP filter determines the final passband applied to the signals; you can adjust the passband center, the width, and/or the low and high cutoff frequencies.

Passband Shift

. . .

Passband Width

. . .

Passband Low Cutoff

. . .

Passband High Cutoff

The Low and High Cutoff controls refer to lower and higher audio frequencies. The Low Cut control affects the low frequencies; the High Cut affects high frequencies. Thus, the RF (and IF) frequencies affected when you change these controls are different for USB and LSB operation. In Figure 4‑3 an interfering station is below you when you are operating LSB or CW. It will sound higher in pitch and so you would use the HI CUT control to reduce it. Conversely, when operating USB (CW REV), Figure 4‑4, if an interfering station is below you, its pitch will sound lower, and you would use the LO CUT control.


Figure 43. LO-CUT and HI-CUT operation for LSB, CW, and DATA.


Figure 44. LO-CUT and HI-CUT operation for USB, CW REV and DATA REV.


IIR or FIR Filtering

. . .

DSP Normalization

. . .

Filter Preset I or II

. . .

Reverse CW

. . .

Dual Passband Filter for CW

. . .

Dual-tone Filter for AFSK A and FSK D RTTY

. . .

Audio Peaking Filter – APF

4.2    Notch Filter

. . .

Automatic Notch

. . .

Manual Notch

. . .



Practice using the notch control.

 · · · 

Tune to an AM station in the broadcast band using SSB instead of AM. Tune slightly off the zero beat frequency until you hear the carrier and then tap NTCH. The carrier should magically disappear. Switch to CW and try manually tuning out the carrier.


4.3    Noise Reduction

. . .

4.3.1    Noise Blankers

Hardware IF Noise Blanker

. . .

DSP Noise Blanker

. . .

Considerations for Both Noise Blankers

1.     Both noise blankers can be used together, with the IF noise blanker operating on one type of noise and the DSP blanker on another. It is best, however, to try them one at a time.

2.     When adjusting a noise blanker level, do so slowly.

3.     If the NB icon is flashing slowly, the IF noise blanker width and/or level are set too high for the present signal conditions and should be reduced.

4.     Both noise blanker's settings are saved on a per-band basis and if CONFIG:NB SAVE is YES, the on/off status is saved per-band. With this you can have a noise blanker turned on for, say, 80 meters and off for 20 meters. When you return to 80 meters, the noise blanker will be turned back on.


4.3.2    DSP Noise Reduction

. . .

Some K3 users complain about the receiver being “noisy”. By using the attenuator, preamplifier, and RF gain control you can adjust the K3 receiver’s audio noise level. You will want to do this on each of your operating bands and you may have to make adjustments as band conditions change. The idea is to set the attenuator and preamplifier and adjust the RF gain control so that the noise on the band is only just audible. Here is a procedure to do this.

1.     Choose the operating band and tune to a frequency with just noise, no signal.

2.     Set the RF gain control fully clockwise.

3.     Choose preamplifier and/or attenuator settings so the noise level is just flickering the S-meter at about S-1 (or as low as you can go, depending on how noisy the band is). The preamplifier and attenuator settings shown in Table 4‑1 should be fairly close.

4.     If the band conditions are very noisy, turn the RF gain control counterclockwise until the S-meter noise just stops flickering.

5.     You can leave your RF gain settings like this and use the AF gain control to set a comfortable listening level.

A good technique to remember if operating in a contest with many signals on the band is to turn the attenuator on in addition to reducing the RF gain.


Table 41.  Using the preamplifier and attenuator.

Band and Conditions



160 meters



80 meters



40 meters


Sometimes On

30 meters


Sometimes On

20 meters



17 meters



15 meters

Sometimes On


12 meters



10 meters



6 meters

PR6 On


Very noise band conditions



Very busy band in contests





4.4    Digging Out that DX Station

That DXpedition you need to work to complete your DXCC award is nearing the end of its stay on its remote island, but so far you haven't been able to break through the wall of callers to get into the log. Working DX involves skills that you can practice to improve your chances. The most critical of these is the ability to find the station the DX is working and then to be able to set your transmitter on that frequency to be the next station worked.

4.4.1    First You Have to Find the DX

. . .

4.4.2    Operating Split with a K3 without a Sub Receiver

. . .

Listen for the DX Operator's Operating Pattern

. . .

Timing is Everything

. . .

Up, Up

. . .


. . .

4.4.3    Operating Split with a K3 with a Sub Receiver

. . .

4.4.4    CW DXing

. . .

4.4.5    DXing with the P3 Panadapter

The P3 Panadapter makes it almost too easy to find DX stations and their pileups. Tap DISPLAY to activate the waterfall display. Tap SPAN and reduce the span to a few kHz, depending on the size of the pileup. You may wish to hold CENTER to move the DX station's frequency to the left side of the display to get the widest display of the pileup. Be sure to enter split mode as described above and then tune VFO B to the station you see (and hear) working the DX. If there are many stations in the pileup, you may use the P3 to find an less crowded valley in the spectra near the last caller to make your call. Again, this works best with the optional KRX3 Sub receiver. See Figure 4‑9 Chapter 9 discusses the P3 Panadapter in detail.


Figure 49.  Using the P3 in a pileup.


4.5    Oops, Why is it doing That?

A feature, and a problem, with radios that implement so much of their functionality in software, such as the K3, is that many functions are programmable and it is difficult to keep track of the radio's current configuration. This can be a problem because we can find ourselves with the radio not operating as we hoped and expected. There are 25 two-function buttons, six multi-function knobs, six programmable function keys, 13 main menu items, and 100 (at last count) configuration menu items. No wonder we get confused at times.

In addition to the Troubleshooting section in the Owner's Manual, which shows error messages that you might see and other troubleshooting tips, here are some "gotcha's" that have been posted to the Elecraft email list server. If you can't solve your problem with hints from the Owner's Manual or this list, try searching the email reflector archive. If no luck, then post your question to the reflector, where plenty of expert advice is available. But do try the archive first, so you won't be the gazillionth owner to ask the same question.


I get audio only in my left earphone:  You probably have CONFIG SPKRS=1 and SPKR+PH set to yES. Either set SPKR+PH no or SPKRS=2.

When I switch on AFX, I can hear the effect in my headphones but not in the K3's speaker: This is normal. The K3 speaker must output a monaural signal.

When using Line Out to drive externally powered speakers, I get audio only in the left channel when the Sub receiver is turned off: This is normal. The Line Out has the Main receiver on the left channel and Sub receiver on the right channel. You can set CONFIG:LIN OUT =PHOnES to have the left and right Line Outputs match the headphone outputs. The level will be controlled by the AF/SUB gain controls.

When I try to use the APF, I get ringing that makes it useless for me: You might try setting a wider DSP bandwidth filter. Some operators find that a 400 Hz filter is better than a 50 Hz filter.

When I turn on NB or NR, I hear lots of garbage:  You probably have the NB and NR settings too high. Try reducing the settings.

My receiver sounds like it is dead: The noise reduction algorithms are so good that they can reduce all receiver noise to nearly zero. Check to se if NR is turned on. Also, check to see if your squelch control is on and set too tight.


After I turn on the rig, the VOX control is turned off:  For CW, a control in CONFIG:CW WGHT (tap 4) can turn VOX off when the rig is turned off. You would enable this to avoid keying the radio when powering on a PC connected to the K3's serial port. You can remind yourself about this by programming a sign-on message such as VOX OFF using the K3 Utility program.

I get some low-level transmit spurs above and below my transmit frequency when operating CW: These were found to be caused by the sidetone in the speaker causing microphonics in the synthesizer. Using headphones with the internal speaker turned off should eliminate this problem. A stiffener modification from Elecraft[1] can be added to the synthesizer board(s) to cure this problem.

When I connect an external keyer to the KEY input, the decoder does not work for my transmitted CW: The CW decoder only works for the internal keyer using the PADDLE input.

When I have VOX and QSK off and PTT not active and I send CW with the paddle, the relays in my amplifier clatter. I am not actually transmitting a signal and this is most annoying:  Sorry. This is normal operation. The KEY OUT is designed to follow any keying signals.


My K3 gets warm on the front, right-side panel: This is normal. The 5- and 8-volt regulators use that side panel for a heat sink.

How hot can the PA temperature get before there is a problem?: A HI TEMP warning will occur if the PA temperature reaches 84° C. You might get an erroneous high temperature warning if you have a low battery voltage when operating at high power.

A hint for miscellaneous weird things happening: RF in the shack can cause the K3 to act strangely. If a bit gets changed in the K3's control software, you can often reset things to normal by turning the power off and then back on. You may also want to consider reloading all firmware and restoring an earlier configuration. Then try to track down and eliminate the reason for the RF in the shack – it is never a good thing!

My K3 has experienced a MCU load failure. I have followed the procedure in the help file in the K3 Utility program but it still fails to load properly: The help file procedure should work properly. You must make sure to follow the procedure exactly. It may help to leave the K3's power off for more than the suggested 30 seconds and it may help to re-boot the computer, reload the K3 Utility and close the port before reconnecting the power to the K3. Also, make sure you do not have any other devices between the computer and the K3 except for an USB-Serial adapter if you are using an USB port. Operators have reported problems downloading software when using a microHAM interface. If you have a computer with an actual RS232 serial port, you may want to try that.

I can't switch to FM mode: CONFIG:FM MODE may be set to OFF.

I can't program a CW message using an external keyer: This can be done only with the internal keyer or the K3 Utility program.

I can't get my K3 and computer to talk to one another: This is a common problem. Please have a look at Appendix B, which describes troubleshooting techniques to find serial port problems.

Noise Reduction

When I tap NR, it does not work. All I get is N/A: Noise reduction does not work with AGC OFF. Check to see the AGC-F or AGC-S icon is showing. If AGC is off, hold OFF to turn it back on.


I get an ERR 12V message:  One operator found that re-crimping the leads on the wires attached to the 12 V circuit breaker solved the problem. If you have an earlier model K3, you may be having problems with the contacts where the PA plugs into the RF board. Later serial number K3's use gold-plated contacts instead of the earlier tin-plated ones. You should contact Elecraft support for suggestions on solving this problem.

When I hold TUNE I get 100 watts out and I'd like less to tune my amplifier:  You can set CONFIG:TUN PWR to any power level you like when holding TUNE.

When I hold TUNE, I don't get the output power I set using the PWR   knob:  Check to see if CONFIG TUN PWR is nor. You can set the tune power to any value to be able to tune an external amplifier at a lower output power by adjusting this configuration menu.

When I hold TUNE, my display shows dB and mW and my receiver seems dead: The CONFIG:KRX3 menu has probably been set to tESt. Change it back to nor.

When I tap ATU TUNE I see 5.0 W displayed instead of the 100 watts I have the set for the power out: This is normal. The ATU uses 5 or 10 watts output to tune the antenna.

I only get 12 watts out when turning the PWR Æ  knob: Check to see if the KPA3 is installed. CONFIG:KPA3 should be nor.

RF Interference

I seem to be getting RF pickup on the RS232 port:  An Elecraft application note, Improving the Immunity of the Rear-Panel RS232 and Audio Connectors to RF will show you how to remove some RF chokes in the ground leads to cure this situation.

I seem to be getting RF into my transmitted audio through the front panel microphone:  An Elecraft application note, Front Panel Microphone Circuit Modification will show you how to remove some RF chokes in the ground leads to cure this situation.


When operating RTTY, changing bands changes from FSK D to AFSK A: The data mode is saved on a per-band basis. Hold DATA MD and select the data mode you want for each band.

I am trying to decode RTTY with the internal decoder and all I get is garbage: Check that the RTTY baud rate is set up properly. Hold DATA MD and tune VFO A for 45 or 75 bPS. 45 bPS is the most common Baud rate.

RTTY mark and space tones aren't right: Go to DATA mode and then hold PITCH and set the MARK tone to 2125 or to the value required in your RTTY software.

When running in DATA A mode for AFSK A or PSK-31 and the rig is keyed, and I can hear audio with the monitor but no tones are transmitted:  Check to see you are not in TEST mode (TX indicator flashing). Check the ALC adjustment. The ALC should be reading about 4 bars with the 5th just flickering.


When I am in sideband, I do not get any power out: Check to see if you need to turn bias on for your microphone and that the front panel or rear panel microphone is selected. See Chapter 3 and Appendix A for more information.

Sub Receiver

When I turn on the K3 I see ERR DSE on the display: This can occur if you have enabled CONFIG:KRX3 when the Sub receiver is not installed. The error message indicates that a request has been sent to the DSP but no response has been received. By holding CONFIG several times you cycle through ERR DS3, ERR BP3 and ERR IF2, all related to the missing Sub receiver. Finally, you will be able to hold CONFIG and change KRX3 to not inSt.

When I switch to diversity reception, I don't have any signal in the right earphone:  Switching into diversity reception automatically switches the Sub receiver to the AUX antenna. If you do not have an antenna on the AUX RF BNC (when CONFIG:KRX3 Ant=bnc) or ANT 2 (when CONFIG:KRX3 Ant=Atu), you won't hear signals from the Sub receiver.

I get the message USE AUX when I switch on the Sub receiver: You will get that message if the Sub receiver is tuned to a higher frequency band than the Main receiver. See Chapter 5 for more information about dual-band reception.


VFO B is changing with VFO A on some bands: You can link VFO B to VFO A by holding SUB about 1/2 second. This can be done in K3s both with and without a Sub receiver. The VFO linked status is saved per-band, and when the VFOs are linked, the kHz decimal point in VFO B slowly flashes. To unlink them, change to the band where they are linked and hold SUB again.

Holding SPLIT gives SPL N/A: You cannot operate split across different bands (cross-band split) or cross-mode split, except for CW/SSB on the same band. If you see this message, VFO B is on a different band or different mode. Tapping A®B at least once to transfer the band information before holding SPLIT is a good practice. You can keep VFO B from being on a different band by setting CONFIG:VFO IND no.

 BAND  does not change to each band, some bands are skipped: Check CONFIG:BND MAP to see if the missing bands have been mapped out.

When I switch between CW and SSB my VFO A frequency changes: See CONFIG:CW WGHT and tap  5  to set VFO OFS to VFO NOR.

When I have the radio in split, after I turn the power off and then back on, it is no longer in split:  You need to set CONFIG:SPLT SV to yES.

When I tap M>V and select a memory that has both VFO A and VFO B frequencies stored, if VFO B is on a different band, it does not change to the band in the memory:  This is normal behavior when you  have configured the VFOs to operate on separate bands with CONFIG:VFO IND yES.


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