K3 Operating Tips

Learning how to use a modern amateur radio transceiver can be a daunting task. We encourage you to read the Owner's Manual, of course.  But as one of the creators of the K3, I have my own list of favorite features that I'd like to introduce you to. These "Operating Tips" are listed below, and more will be posted both here and on the Elecraft reflector in the future.




K3 Field Day Note: QRO/Battery    

AFX (audio effects)

Adding text labels to ANT1 and ANT2

Viewing and manually adjusting ATU L-C settings

RTTY operation without a computer

Copying the RIT offset to VFO A & other RIT/XIT techniques

How to do RIT (sort of) with the "BIG" knob

Special display modes (Time, Voltage, Temperature, etc.)

Setting up your K3 for PSK (and other audio-based digital modes)

Lyle Johnson, KK7P, explains Noise Reduction

Menu Help Text and Factory Default Settings

Operating at 500 kHz

June 10, 2009

Operating at 500 kHz

A few countries allow experimental amateur radio operation in the 500 kHz band (600 meters). This is a fascinating and historic band that is used for beacons and ground-wave communications. For hams, there are very specific mode and power restrictions, and an experimental license may be required. In the U.S., see http://www.500kc.com/ and http://www.arrl.org/  for the latest news.  The K3 can be used for both receive and transmit on this band as explained below.

 500 kHz Receive-Only Operation

The K3 can receive signals in the 500-kHz band if both the KXV3 and KBPF3 modules are installed.  The KXV3 (RF I/O module) is needed because it provides an RX ANT IN jack. This jack bypasses the high-pass filter in the normal receive antenna path. At 500 kHz, the high-pass filter--which protects the T/R PIN diodes--will attenuate signals by about 20 dB. There is no such attenuation at 500 kHz when using the RX ANT IN jack, and sensitivity is excellent. We measured an MDS of -133 dBm with preamp OFF and a DSP filter bandwidth of 50 Hz.  The KBPF3 (general-coverage module) is needed because the normal 160-meter band-pass filter covers only about 1.7 to 2.1 MHz. The KBPF3 includes a low-pass filter that passes signals down to 500 kHz with very little attenuation.  A low-noise receiving antenna is recommended for use at 500 kHz.

 Diversity receive should be very useful at 500 kHz. To do this, you'll need a sub receiver (KRX3) that is equipped with its own KBPF3 module.  You'll also need a separate receive antenna for the sub, oriented differently from the receive antenna used with the main receiver.   

500-kHz Transmit/Receive Operation

The K3 cannot be used to directly transmit on 500 kHz at high power.   The low-pass filter cutoff frequency is well above that needed for attenuation of harmonics on this band, and other components in the transmit path are optimized for 1.8 MHz and higher.  However, the K3 can put out a clean 500 kHz signal of about 0.5 milliwatts at the XVTR OUT jack (on the KXV3). This can be fed to an external amplifier (this is left as an exercise for the reader).  Transmit power is restricted on this band, and is usually expressed as ERP (Effective Radiated Power). This means you can use high power to make up for the use of an electrically short antenna. Since 1/4 wavelength at 500 kHz is about 468 feet, not many hams will be using a full-length vertical or dipole. 

As with receive, transmit at 500 kHz requires the KXV3 and KBPF3 modules. In this case, though, you'll need to use the XVTR IN and XVTR OUT jacks, with XVTR IN going to the receive antenna, and XVTR OUT going to your 500 kHz amplifier and a transmit antenna. If the same antenna is used for both transmit and receive, an external T/R switch will also be needed, controlled by the K3's KEY OUT signal. If separate transmit/receive antennas are used, it may be necessary to provide a PIN-diode switch to open or short the receive antenna during transmit. The XVTR IN jack is normally used with a transverter, so it doesn't have such protection built in. 

IMPORTANT: In order to transmit at 500 kHz via the XVTR OUT jack, you  must set CONFIG:KXV3 to TEST. This routes all signals through XVTR IN and XVTR OUT, which is why the receive antenna must be connected to XVTR IN in this case. (You can't use XVTR OUT for transmit and RX ANT IN for receive due to switching limitations.) Be sure to set KXV3 back to NOR when using normal ham bands.

If interest in the 500-kHz band is sufficient, we'll change add 160 meters as an IF band for use with transverters. This would allow you to set up a 500 kHz transverter band, so it would not be necessary to set KXV3 to TEST.

Synthesizer Considerations

Before using 500 kHz, you'll need to make sure your synthesizer is adjusted to cover this band. Tap DISP and use VFO B to locate the "PLL1" display. If the voltage is less than 0.9 V when VFO A is set, contact customer support for suggestions on how to adjust it. If you plan to transmit on this band, connect an short (3') antenna to the XVTR OUT jack and listen to your signal with another 500 kHz receiver.  Make sure the signal sounds clean.

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Dec. 18, 2008

Menu Help Text and Factory Default Settings

Sometime when you're cruising through the K3's menus, wondering what some of the entries are for, try tapping DISP. This will show help information for the current menu entry.  For example, if you're in CONFIG:SMTR PK, tapping DISP will show:


If a value in parentheses is shown at the start of the text, it's the factory default; this is useful if you want to set some things back to their original values. (Some entries, like CONFIG:FW REVS, don't have a
default.) You can tap any switch to cut off the scrolling help text before it finishes.  So, you think the CONFIG menu doesn't have enough entries? That means you probably have CONFIG:TECH MD (tech mode) set to OFF. Set it to ON and stand back ;)

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June 27, 2008

K3 Field Day Note: QRO/Battery

The K3 can be used at QRO power levels (13-100 W) when powered from a car battery or a large gel cell. Here are a few things to keep in mind:

- A battery that's significantly discharged will have higher internal resistance, which will cause the voltage to drop when high current is drawn. (Small-gauge battery cables should also be avoided.)

- You can monitor your battery's vital signs during RX and TX using the K3's built-in voltmeter and ammeter. Just tap DISP, then rotate VFO B to see the voltage or current.

- The specified minimum supply voltage for the K3 is 11 V. This is a conservative rating, intended to ensure spectral purity and stability.  But maximum power output will drop almost linearly with supply voltage.  You'll typically get 100 W at 12 V and about 75 W at 11 V. At 10.5 V, you should drop to QRP levels. Below 9.5 V the rig may turn itself off.  Reduce the power setting manually when voltage drops, just to be safe.

- If you see an unexpected "HI TEMP" warning during QRO transmit, it could be due to an excessive dip in battery (or generator) voltage at the PA monitor circuitry. If you see this happen, try configuring the temperature sensor to sample only during receive mode. To do this, locate the PA TEMP menu entry (CONFIG menu), then tap the '1' key until you see "R ONLY" (rather than the default, "T AND R"). This mode of  operation is completely safe as long as you're not "standing on the key" for several minutes at a time.

March 2, 2008

Setting up your K3 for PSK (and other audio-based digital modes)

The K3 is an outstanding platform for operating digital modes. It already has dedicated direct FSK and PSK with your CW paddles. But there is also an option to use Data-A mode to operate PSK or any other audio based digital mode in conjunction with soundcard-based digital mode software.

It is usually best to use a second soundcard for your audio-base digital modes. This way you will not be plagued with Windows sound effects in your waterfall or in your transmitted signal. If you do not have that option, you can always go into your Windows control panel and open “Sounds and Audio Devices.” Select the Sounds tab and set Sound Scheme to No Sounds.

Here are the steps to setup for PSK using Data-A mode:

1. Set your soundcard volume to about 50%.

2. Connect soundcard output to the K3 LINE-IN.

3. Connect the soundcard input to the K3 LINE-OUT.

4. Set Menu item MIC SEL to LINE IN. The K3 will remember this MIC SEL source next time you use digital modes.

5. Set mode to DATA. HOLD DATA MD to choose Data-A using the VFO B knob.

6. Set power to ~20W (just something to start with).

7. Use the MIC control to set the drive level so that your see 4 bars of ALC and output is equal to, or just below what you dialed in (20W in this case). Compression is locked at zero automatically when in Data mode and cannot be adjusted.  When setup this way I get excellent PSK31 results with TX IMD at ~ -26 dB to -32 dB - a very clean signal.


You can use a separate line for PTT from a computer COM port to the ACCY connector or the RCA PTT connection on the back of the K3. This requires a simple circuit using a transistor and resistor between the COM port and the K3. You can find this circuit on many ham radio websites, including the AA5AU RTTY website.  You can also use the RS-232 serial connection if your software allows you to set it up that way. Not all software allows you to do this. Some programs will also allow PTT via CAT command. 

In the K3 CONFIG menu, set PTT-Key to either RTS - OFF or DTR - OFF. Then in your software set PTT to either DTR or RTS as appropriate to the same COM port the radio is connected to.

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Feb. 19, 2008

Special display modes (Time, Voltage, Temperature, etc.)

The VFO B display normally shows the VFO B frequency. As you've probably discovered, it also shows decoded CW or DATA-mode text, menu entries, memory numbers and their labels, and the RIT/XIT offset (as you turn the offset knob).  You can also set up the VFO B display to show a variety of useful system parameters, including:

Time (24-hour)
Date (US or EU format)
Supply voltage
Current drain
KPA3 heatsink temperature
Front panel compartment temperature

If you have the TECH MD menu entry set to ON, the list expands to include PLL voltages, audio output voltage (AFV), and dBV (audio level relative to most recent AFV reading). The latter is very useful for comparing signal levels (usually, you'd turn AGC OFF in this case).  To access these special displays, simply tap DISP, then rotate VFO B until you find the display of interest. Tap DISP again to return to the normal VFO B display.

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Jan. 12, 2008

How to do RIT (sort of) with the "BIG" knob

For those who would like to use the large VFO A knob as if it were RIT, there's a setup just for you.

Once you have your base frequency (or RUN frequency in a contest) TAP A>B to send the VFO A frequency to VFO B. Then place the K3 into SPLIT mode. Your TX frequency will not change, but now you can tune your RX frequency with the VFO A knob to tune in those stations calling who are slightly off frequency.

In the CONFIG menu there's a B>A function that you can assign to one of the programmable buttons. This feature allows you to pick up your TX frequency from VFO B to match your RX frequency on VFO A.

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Jan. 11, 2008

Copying the RIT offset to VFO A & other RIT/XIT techniques

If you've tuned in a signal using RIT, but would then like to move VFO A to that frequency, simply hold the CLR (RIT clear) button for 2 seconds. You'll see "OFS->VFO" flash on VFO B briefly, the RIT offset will be cleared, and the green LED above the offset knob will turn on.  The VFO A display itself will remain unchanged, because it always shows the effect of any RIT offset anyway.

Example: Suppose VFO A is tuned to 14250 kHz, and you're tuning around this frequency using RIT. You find a station calling CQ who's off by +0.30 kHz, so the VFO is now reading 14250.30 (RIT offset = +0.30). Just before calling, you hold CLR for two seconds to move VFO A up to this frequency, so that your transmit and receive frequencies are equal. The RIT offset is now 0.00.

Another way of accomplishing the above is to turn on both RIT and XIT at the same time. The offset that was in effect for RIT (receive) will then also apply to XIT (transmit). In effect, this turns the offset control into a limited-range VFO knob that covers +/- 9.99 kHz around a given VFO A frequency.

Note that the RIT/XIT tuning resolution always matches that of the VFOs. So if you want to tune the offset in 1-Hz steps, just tap FINE.  For large steps, hold COARSE.  When both RIT and XIT are turned off, you can use the offset knob as a COARSE tuning knob. This requires setting CONFIG:VFO OFS to ON.  Be careful, though -- if you frequently use RIT in contests, you may want to leave this feature turned off to avoid moving the VFO in large steps accidentally. OFF is the default.  The COARSE VFO step size can be set per-mode, using the CONFIG:VFO CRS menu entry. This step size applies to both the COARSE tuning rate of VFO A and B and to the offset knob function described above, if enabled.

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Dec. 28, 2007

RTTY operation without a computer

If you're a CW operator but would like to dabble a bit in RTTY (especially easy during a contest), you're in luck: You can use the K3's internal keyer to directly transmit RTTY. You can also copy RTTY on the K3's text display, making it a self-contained RTTY station -- no need to set up computer cables or software.  Just follow the procedure below (all parameters are saved, so you'll only need to do the setup one time).

1. Tap either end of MODE to get to DATA, then hold DATA MD and select FSK D.

2. Hold PITCH and select a mark tone; I use 915 Hz.

NOTE: No matter what pitch you select for FSK D mode, the K3's VFO will always show you your mark frequency. Thus there's no need to do any math to convert from an SSB suppressed-carrier frequency to the actual data carrier frequency. This makes RTTY operation very similar to CW:  just tune in a signal and call them using the keyer paddle.

3. Hold TEXT DEC and turn the text decoder. You'll start seeing random noise characters on the VFO B display.

4. Tap CWT; the upper half of the S-meter will become a RTTY tuning aid. When tuning in signals, try to get the mark and space tones balanced in their number of bars on either side of the CWT pointer.

5. Set power to the desired level. The K3 can transmit at full power in RTTY mode.

6. Plug in a keyer paddle. Adjust the sidetone volume in CW mode (if necessary), then switch back to DATA mode.

7. Send a few characters with the paddle. If you don't hear the FSK signal, adjust the MONitor level (hold the CMP/PWR knob in to select MON level adjust). Note that you can adjust the levels in TX TEST mode, too, without putting out any power. This is a good way to practice with CW-to-RTTY.

8. If you pause, the K3 will remain in a data idle state for about 4 seconds before automatically returning to receive mode. To cut the 4 second timeout to about 1 second, you can send "..--" (IM prosign, for "IMmediately exit").

For further details, see the Owner's Manual, page 32 (revision C).

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Dec. 20, 2007

Viewing and manually adjusting ATU L-C settings

Most of the time you'll let the KAT3 automatic antenna tuner do its thing and ignore it. It has a wide matching range and saves L-C information per-band and per-antenna, so you'll rarely need to re-tune. (We do plan to add multiple stored segments per band, too.)

If you're ever curious about the actual L and C values used in the matching network, you can check them using a special setting of the KAT3 menu entry (in the CONFIG menu). Just set KAT3 to LCSET, then exit the menu. Next, tap "ATU TUNE". This will display the present L and C values.

For example, I just matched my K3 on a random wire antenna on 40 meters, went into LCSET mode, and saw this when I tapped ATU TUNE:

CA 0.08 nF
L 0.25 uH

The "CA" means that the capacitance ended up on the antenna side of the L-network. The other possibility is "CT", or capacitance on the transmitter side. The capacitance is shown in nF (nanofarads) so it can fit into three digits on the VFO A display even when the value is over 999 pF. The value shown, 0.08 nF, could also be expressed as 80 pF.

Now, suppose you'd like to see what the effect of changing the L and C values would be on the match. (Or you're troubleshooting the KAT3.) You can simply rotate VFO A to change the C value, and rotate VFO B to change the L value. Tapping "ANT" alternates between "CA" and "Ct". Having made a change, tap ATU TUNE again to exit the L-C display. Then hold TUNE to go into transmit mode and see the new SWR value.

Manual view/change of LC settings is certainly fun and educational. But it could also be used to give me (your overworked firmware guy) feedback about a difficult matching situation. I'm always open to fine-tuning the KAT3's algorithm. So if you discover -- using LCSET -- that you're able to do better than the KAT3 in auto-tune mode, just let me know.

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Nov. 29, 2007

Adding text labels to ANT1 and ANT2

 If you have a K3 with the internal automatic antenna tuner installed (KAT3), you can assign text labels to each of the two antenna jacks (ANT1 and ANT2). Once you've assigned a label, tapping the ANT switch
 or changing bands will briefly flash the antenna name. This serves as a reminder of which antenna is in use -- especially useful for those of in the 50 And Beyond club.  For example, if you have a triband yagi and a dipole connected to the K3, you might name them "YAGI" and "DIPL".

One good reason to assign names to the antennas: you may want to A/B test antennas on individual received signals. The ATU covers a wide matching range, allowing you to use each of the two antennas on bands  outside their design frequency range. So, you could end up with several bands on which both antennas are useful. This is especially true during field outings, where you might have two long-wire antennas oriented in different directions.

 Here's how to assign names:

 1. Select ANT1 or 2 by tapping the ANT switch.

 2. Hold the ANT switch until the antenna symbol and blank text field appears on the VFO B display.

 3. Use VFO A to select which character to change.

 4. Use VFO B to select a character (A-Z, 0-9, and various symbols).

 5. After selecting all characters, tap ANT to return to normal operation.

 This is covered in the Owner's Manual under Basic Operation/Antenna Selection and Matching (page 22 of the rev C manual).

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Nov. 18, 2007

AFX (audio effects)

If you have stereo headphones and/or two speakers plugged into your K3, you can use the AFX (audio effects) function. This creates a simulated stereo or binaural audio "space" that is hard to describe -- you'll just have to try it :) For some operators it reduces listening fatigue when compared to monophonic audio, and can even help improve signal copy.

To use AFX, simply tap the AFX switch (just above the VFO B knob).  You can select different AFX variations using the AFX MD menu entry (MAIN menu). I prefer DELAY 5, which is the default. "BIN" creates
binaural audio via phase shifting, while DELAY1-5 simulate stereo using a short delay between the left and right channels.

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