ELECRAFT K3 Specifications
Key Measurements
product review
Elecraft K3/100 HF and
6 Meter Transceiver
142† 140
20 70
20 kHz Blocking Gain Compression (dB)
2 kHz Blocking Gain Compression (dB)
106 110
20 50
20 kHz 3rd-Order Dynamic Range (dB)
Reviewed by Joel R. Hallas, W1ZR
Technical Editor, QST
The Elecraft K3 is a modular and expandable transceiver that can be set up to
fill a number of roles. In our first look, we
described a configuration at the bottom of the
K3 spectrum — a 10 W minimally equipped
kit version of the transceiver.1 At that time,
many of the announced options were not yet
available. This time, we have waited until
almost all of the bells and whistles have been
installed and configured.
In addition to the pieces included for the
earlier review, this version has the following
hardware as well as the benefit of multiple
firmware revisions:
An internal power amplifier module
(KPA3) that makes the K3 into a nominal
100 W output transceiver on 160 through
6 meters.
A second receiver (KRX3), identical in
performance to the first, that fits in the same
box. Two audio channels are provided so one
receiver can be heard in each ear or speaker, or
they can be mixed. In split mode, one receiver
can track a DX station’s receive frequency
and control the transmit frequency, while the
other is listening to his transmission. The two
receiver VFOs can be locked together to provide diversity reception to avoid fading. This
works if you have two separated antennas or
antennas of different polarization.
A transverter interface (KXV3) that
also provides a connection for a receive-only
antenna and an IF output for a spectrum
An automatic antenna tuner (KAT3)
specified to match antenna loads with an
SWR up to 10:1. The KAT3 also provides a
switchable second antenna connection.
General coverage receiver front end
band-pass filter (KBPF3), AM, SSB, CW
and FM roofing filters (see text) and the
KTCXO3-1 temperature controlled frequency reference that provides stability of
better than ±1 ppm over the operating temperature range.
The only announced options that weren’t
yet available for testing were the digital voice
recorder (KDVR3) and the low noise 6 meter
receive preamp (PR-6).
The resulting radio looks the same as the
K3/10 from the front, but it weighs a tad more
and the rear panel has quite a few more connectors. As you might expect, the options result in
a significant increase in the total cost. While
the base 10 W kit costs $1400 at this writing,
our fully assembled and tested radio is about
$4000 ($3350 for the radio and modules, plus
$600 for five optional roofing filters).
A nice feature of the K3 architecture is that
it doesn’t have to be purchased all at once, nor
are all options required to have a fully functional competitive transceiver — build it your
way. Start with as much of a chunk as you’re
comfortable with and then add pieces over
time. It also makes filling out holiday wish lists
an easy chore, possibly for years to come!
Does Size Matter?
So What’s in This Little Box?
Prior, N7RR, “First Look: Elecraft K3 HF/6
Meter Transceiver,” Product Review, QST,
Apr 2008, pp 41-45. QST Product reviews
are ­available on the Web at www.arrl.org/
We should emphasize that this is indeed
a compact and, at just a few pounds more
than the K3/10, still a light transceiver. At
Mark J. Wilson, K1RO  Product Review Editor  2
103 110
2 kHz 3rd-Order Dynamic Range (dB)
29 +35
20 -40
20 kHz 3rd-Order Intercept (dBm)
28 +35
2 kHz 3rd-Order Intercept (dBm)
TX -20
Transmit 3rd-Order IMD (dB)
TX -20
Transmit 9th-order IMD (dB)
Key: † Off Scale
Dynamic range and intercept
values with preamp off.
Intercept values were determined
using -97 dBm reference
80 M
20 M
Bottom Line
The K3, in any of the available
configurations, provides a high performance, modular and expandable
transceiver that can fill the needs of
almost anyone looking for an HF and
6 meter transceiver for home station
or portable use.
[email protected]
From January 2009 QST © ARRL
a size about the same as the compact entry
level radios from other manufacturers, this
radio includes many features found in the
largest and most expensive radios on today’s
market. Its performance is comparable or
superior in most respects as well. On the
other hand, there just aren’t as many knobs
and switches on the front of this radio as its
larger brethren. Elecraft uses each button for
at least two functions. The one shown on the
button happens with a quick tap. A secondary, often related, function, shown below the
button, is enabled with a longer, 1⁄2 second
or more, push. It doesn’t take long to get the
fingers programmed. The buttons and knobs
are organized into groups by function, and I
had no problem getting to know them.
While size and weight are of particular
importance to those who want to take the
radio with them as they travel, or who operate
in close quarters, front panel space is limited.
Controls are somewhat smaller and closer
together than on some larger radios, although
I found them all accessible and easy to use.
Perhaps the display provides the biggest difference. The K3 includes a two-line
monochrome LCD that shows all critical operating information. It doesn’t offer the bells
and whistles of the “big boys,” particularly
a spectrum analyzer — perhaps expected at
the upper end of the K3 price range. An IF
OUTPUT jack is provided (as part of the optional KXV3 transverter module) so that an
external spectrum scope can be supported. At
least one manufacturer provides a very competent one that works with a PC and provides
“point-and-drag,” frequency selection.2
Thus, with an added spectrum scope for
home station operation, the combination of
displays can rival top-end transceivers. At
the same time the basic radio remains ready
for the campground or emergency operations
center. For some, this will be the best of
all worlds. Those who don’t travel or don’t
need the compact footprint may wish it were
somewhat larger.
How’s it Play?
In a word, this is one fine radio. I was so
impressed with its published performance
that I will happily confess to having purchased a 100 W kit version for myself. I don’t
think that makes me biased, since I’ve had
much more cockpit time to get to know the
K3, for better or worse, than most equipment
I’ve reviewed over the years. The ARRL Lab
measurements were taken with a current
production radio. We’ve also spent quite a
bit of time using an early production K3/100
that’s been upgraded as accessories and new
firmware have become available.
software defined IQ direct conversion
panadapter for the K3. Available as a kit or
fully assembled from Larry Phipps, N8LP, at
From January 2009 QST © ARRL
Table 1
Elecraft K3, serial number 1915
Manufacturer’s Specifications
Measured in the ARRL Lab
Frequency coverage: Receive, 0.5-30,
48-54 MHz; transmit, 1.8-2, 3.5-4, 5.33-5.40,
7-7.3, 10.1-10.15, 14-14.35,18.068-18.168,
21-21.45, 24.89-24.99, 28-29.7, 50-54 MHz.
Receive and transmit, as specified.*
Power requirement: 11-15 V dc; transmit,
17-22 A; receive, 0.9 A (without subreceiver).
As specified. Operation confirmed
at 11 V.
Modes of operation: SSB, CW, AM, FM, FSK,
AFSK, PSK, data.
As specified.
Receiver Dynamic Testing
SSB/CW sensitivity, 500 Hz bandwidth:
Noise Floor (MDS), 400 Hz bandwidth:**
–136 dBm (typical), preamp on.
Preamp Off Preamp On
1.0 MHz
–111 dBm
–119 dBm
3.5 MHz
–131 dBm
–138 dBm
14 MHz
–130 dBm
–138 dBm
50 MHz
–130 dBm
–136 dBm
Noise figure: Not specified.
14 MHz, preamp off/on: 12/9 dB.
AM sensitivity, 6 kHz bandwidth, 10 dB S/N:
10 dB (S+N)/N, 1 kHz, 30% modulation:
Not specified.
Preamp Off Preamp On
1.0 MHz
15.6 µV
10.6 µV
3.8 MHz
1.6 µV
0.9 µV
50 MHz
2.1 µV
1.6 µV
FM sensitivity, 12 dB SINAD: Not specified.
For 12 dB SINAD:
Preamp Off
29 MHz
0.55 µV
52 MHz
0.62 µV
Preamp On
0.40 µV
0.44 µV
Blocking gain compression: 140 dB typical
Gain compression, 400 Hz bandwidth:**
at 2, 5 and 20 kHz spacing with 400 Hz,
20 kHz Offset 5/2 kHz offset
8 pole roofing filter.
Preamp Off/OnPreamp Off
3.5 MHz
142/137 dB 140/139 dB
14 MHz
142/138 dB 140/140 dB
50 MHz
140/138 dB 128/124 dB
Reciprocal Mixing (500 Hz BW): Not specified.
20/5/2 kHz offset: –112/–100/–86 dBc.
ARRL Lab Two-Tone IMD Testing**
Band/Preamp Spacing
Input Level
3.5 MHz/Off
20 kHz
–23 dBm
–14 dBm
0 dBm
IMD Level
–131 dBm
108 dB
–97 dBm
–60 dBm
+31 dBm
+28 dBm
+30 dBm
14 MHz/Off
20 kHz
–24 dBm
–13 dBm
0 dBm
–130 dBm
106 dB
–97 dBm
–60 dBm
+29 dBm
+29 dBm
+30 dBm
14 MHz/On
20 kHz
–35 dBm
–21 dBm
–138 dBm
103 dB
–97 dBm
+17 dBm
+17 dBm
14 MHz/Off
5 kHz
–25 dBm
–14 dBm
0 dBm
–130 dBm
105 dB
–97 dBm
–59 dBm
+28 dBm
+29 dBm
+30 dBm
14 MHz/Off
2 kHz
–27 dBm
–14 dBm
0 dBm
–130 dBm
103 dB
–97 dBm
–59 dBm
+25 dBm
+28 dBm
+30 dBm
50 MHz/Off
20 kHz
–26 dBm
–11 dBm
–131 dBm
105 dB
–97 dBm
+27 dBm
+32 dBm
Second-order intercept: Not specified.
It’s Got Features
The K3 does almost anything you can
imagine, and some things we didn’t imagine
until we saw them! The latter category most
notably includes the way it can operate popular digital modes in a stand-alone fashion.
It decodes RTTY, PSK31 and even CW
on the display, as do a few other high-end
transceivers — but the K3 also can send in
these modes by internal translation from
Preamp off/on: +75/+75 dBm.**
Morse using keyer paddles. Remarkable
While it seems like a gimmick, it can be
helpful — as when you see a rare station
running RTTY posted on the DX cluster and
you’re operating portable or don’t have your
station set up for RTTY. The short display
space might be a limit for a rag chew, but
not for a DX contact. I’ve actually made such
contacts. The K3 Utility Program, required
FM adjacent channel rejection: Not specified.
Receiver Dynamic Testing
20 kHz offset, preamp on: 29 MHz,
79 dB; 52 MHz, 79 dB.
FM two-tone, third-order IMD dynamic range:
Not specified.
20 kHz offset, preamp on:
29 MHz, 86 dB†; 52 MHz, 86 dB.†
10 MHz spacing: 52 MHz, 104 dB.
S-meter sensitivity: S9 = 50µV, user-adjustable.
14.2 MHz: preamp off, 50 µV;
preamp on, 13.5 µV.
Squelch sensitivity: Not specified.
At threshold, FM, 29 MHz, 0.2 µV;
52 MHz, 0.3 µV.
Receiver audio output: 2.0 W into 4 Ω
at 10% THD.
2.1 W at 10% THD into 4 Ω.
IF/audio response: Not specified.
Range at –6 dB points, (bandwidth): ††
CW (400 Hz): 459-800 Hz (341 Hz); ‡
Equivalent Rectangular BW: 416 Hz;
USB: 211-2750 Hz (2539 Hz);
LSB: 292-2820 Hz (2528 Hz);
AM: 113-2890 Hz (2777 Hz).
Spurious and image rejection: >70 dB First IF rejection, 14 MHz, 105 dB;
50 MHz, 111 dB; image rejection,
14 MHz, 88 dB; 50 MHz, 72 dB.
Power output: HF & 50 MHz: SSB, CW, FM,
100 W, reduced power on AM.
Transmitter Dynamic Testing
HF: CW, SSB, FM, adjustable, 0 to
typically 116 W AM, 0 to 51 W.
Spurious-signal and harmonic suppression: >50 dB on HF, >60 dB on 50 MHz.
MF, 48 dB; HF, 52 dB; 50 MHz, 66 dB.
Meets FCC requirements.
SSB carrier suppression: >50 dB.
>70 dB.
Undesired sideband suppression: Not specified.
>70 dB.
Third-order intermodulation distortion (IMD)
products: Not specified.
3rd/5th/7th/9th order (worst case band):
HF, –29/–43/–46/–51 dB PEP;
50 MHz, –25/–41/–51/–51 dB PEP.
CW keyer speed range: Not specified.
8 to 46 WPM.
CW keying characteristics: Not specified.
See Figures 1 and 2.
Transmit-receive turnaround time (PTT release
to 50% audio output): Not specified.
S9 signal, 25 ms.
Receive-transmit turnaround time (tx delay):
Not specified.
SSB, 12 ms; FM, 9 ms. Unit is
suitable for use on AMTOR.
Composite transmitted noise: Not specified.
See Figure 3.
Size (height, width, depth): 4.4 × 11.1 × 11.8 inches; weight 9.4 pounds.
Third-order intercept points were determined using S5 reference.
Price: (assembled) K3/100, $2089.95; KAT3 internal antenna tuner, $329.95; KRX3
subreceiver, $599.95; KBPF3 general coverage RX band-pass filter, $129.95; KXV3
RX antenna I/O and transverter interface, $99.95; KTCXO3-1 high stability oscillator,
$99.95; 5 pole filters (200, 500 Hz), $99.95 each; 8 pole filters (250, 400 Hz; 1, 1.8, 2.1,
2.8, 6, 13 kHz), $125.95 each.
*Reduced sensitivity around the 8.215 MHz IF. The optional KBPF3 band-pass filter is
required for full general coverage receive performance.
**Receiver testing was performed with the optional 400 Hz, 8-pole roofing filter for optimum
performance unless otherwise specified. Two-Tone, 3rd-Order IMD Dynamic Range
figures comparable to previous reviews are shown on the first line in each group.
The “IP3” column is the calculated Third-Order Intercept Point. Second-order intercept
points were determined using a –97 dBm reference.
†Measurement was noise-limited at the value indicated.
††Default values; bandwidth and cutoff frequencies are adjustable via DSP.
‡Varies with PBT and pitch control settings.
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Figure 1 — CW keying waveform for the
K3/100 showing the first two dits in fullbreak-in (QSK) mode using external keying.
Equivalent keying speed is 60 WPM. The
upper trace is the actual key closure; the
lower trace is the RF envelope. (Note that
the first key closure starts at the left edge
of the figure.) Horizontal divisions are
10 ms. The transceiver was being operated
at 100 W output on the 14 MHz band.
Figure 2 — Spectral display of the K3/100
transmitter during keying sideband testing.
Equivalent keying speed is 60 WPM using
external keying. Spectrum analyzer
resolution bandwidth is 10 Hz, and the
sweep time is 30 seconds. The transmitter
was being operated at 100 W PEP output
on the 14 MHz band, and this plot shows
the transmitter output ±5 kHz from the
carrier. The reference level is 0 dBc, and
the vertical scale is in dB.
for downloading operating software, and
available from the Elecraft Web site, can
also be used to display a continuous streaming page of text from the internal decoder if
you’re connected to a PC.
This radio provides a large number of
interesting features, all described in the downloadable 78 page Operator’s Manual. We will
hit what we see as the high spots and let those
who want to know more go to the source.
Features for Everyone
Some features are there for all modes. The
combination of roofing filters (2.7 kHz standard, room for four more in each receiver)
and DSP bandwidth filters are seamlessly
adjustable in each mode. Just turn the WIDTH
control and set the SHIFT where you want
it and you get exactly the bandwidth you
need — from the widest roofing filter width
down to an amazing non-ringing 50 Hz that
10 2
10 3
10 4
10 5
10 6
Figure 3 — Spectral display of the K3/100
transmitter output during composite-noise
testing. Power output is 100 W on the
14 MHz band. The carrier, off the left edge
of the plot, is not shown. This plot shows
composite transmitted noise 100 Hz to
1 MHz from the carrier. The reference level
is 0 dBc, and the vertical scale is in dB.
From January 2009 QST © ARRL
A Close Look at K3 Roofing Filters
There has been considerable discussion on e-mail groups about which of the
roofing filters to use to fill the five available slots in the K3. These roofing filters
are key to the radio’s superb dynamic performance, and you get to choose which
ones you want. The available filters are either five-pole (at $100 each), made by
Elecraft, or eight-pole (at $126), made for Elecraft by International Radio (Inrad).
The bandwidths available are:
 Five-pole: 200, 500, 2700 Hz.
 Eight-pole: 250, 400, 1800, 2100, 2800, 6000 and 13,000 Hz.
A 2700 Hz roofing filter is standard in both the main and subreceiver. At the
time of order the 2800 Hz filter may be substituted for $96 additional.
There are some limits to choice, however. In the main receiver, either a 2700
or 2800 Hz filter is required for CW and normal SSB transmission, the 13 kHz
FM filter is required for FM operation and the 6 kHz AM filter is required for AM or
extended (to 4 kHz) SSB transmission. The transmit filters must be in the main receiver chain. The subreceiver does not get involved in transmission, so the restrictions don’t apply. We selected a representative sample of filters to determine the
benefits of the narrower filters, a common question on e-mail groups.
The ARRL Lab test results are shown in Table 2. Note that we have included
some data that we don’t usually report on, because we found the results of interest. First we measured the blocking and third-order dynamic range at a 1 kHz
spacing, because we felt the benefit of the narrowest filters would show up more
clearly there. Second, we generally measure from each side of center and show
the worst case reading. Here we have provided both because some of the filters
do not have a symmetrical response.
The results are interesting, and somewhat surprising — particularly the IMD
data. The blocking dynamic range, now termed blocking gain compression, acts
the way I would expect. As the filters get narrower, the close spacing dynamic
range improves rather dramatically. The 2 kHz separation data may be of most
interest to SSB contesters, while the 1 kHz data probably applies most to CW
operators. The IMD data, on the other hand does not quite act as expected —
particularly with respect to the change from 2700 to 1800 Hz filters. The dynamic
range at all spacings is actually somewhat worse with the 1800 Hz filter. It appears,
confirmed with discussions with Elecraft, that the IMD products are actually occurring in the filter itself. This was observed in two samples of this filter and Elecraft
reported that they are working on developing an improved selection process.
So which should you get? For SSB, the gain compression may be most important, so I’m glad I have the 1800 Hz in my radio. It’s worth noting that often adjacent channel SSB transmit IMD products will be signigicantly higher than
those generated in the receiver. I am also pleased with the 400 Hz filter in my
main receiver for tight CW conditions. Two facts are clear — even with the standard filter, this radio is a fine performer, and — better dynamic performance is
possible with sharper filters, but IMD improvement may not be as dramatic as
expected. — Joel R. Hallas, W1ZR
Table 2
K3 Dynamic Performance with Different Roofing Filters
Blocking Gain Compression, (dB) at MDS (preamp off, 14 MHz)
Spacing (kHz)
Roofing Filter (Hz)
Third Order Intermodulation Dynamic Range (dB) at MDS (preamp off, 14 MHz)
Spacing (kHz)
Roofing Filter (Hz)
From January 2009 QST © ARRL
is actually usable on CW. Alternately, you
can set operating bandwidth by setting the
high and low cut frequencies.
The receiver and transmitter performance
are top notch, as shown in Table 1 and Figures 1
through 3. There is no transceiver in the amateur marketplace that has the close-in dynamic
range performance of the K3 with narrow
roofing filters installed, and most aren’t close
to the K3 in stock form. This is a result of the
HF first IF architecture of the radio, currently
shared only with the Ten-Tec Orion. This
allows the use of narrow roofing filters with
excellent shape factor, compared to radios with
the more common VHF first IF. See my sidebar
in a recent Product Review for a discussion of
the different transceiver architectures and their
impact on dynamic range.3
Automatic gain control (AGC) threshold
(the signal level at which the AGC starts to
reduce gain), AGC slope and AGC hold time
are menu adjustable. I like to have the audio
level increase a bit with louder signals, but not
as much as the default provided — an easy
menu setting fixed that. Similarly, the optimum
AGC threshold depends on the ambient band
noise level, so having it adjustable is a big
plus. I set this menu item to come up with a
front panel button so I could adjust it easily
as I changed bands. Two front panel knobs
can be used for instant adjustment of menu
functions. Both a traditional noise blanker and
a DSP based one are independently available
and are effective.
Dual audio streams are provided to either
stereo headphones or stereo speaker connections. If you have the second receiver turned
on, one of the channels is connected to each
receiver. I find this the best way to operate
split frequency for working DX stations. It
currently is restricted to being on the same
band as the main receiver, but the ability
to monitor a different band is high on the
firmware to do list. A number of antenna connection options allow different antennas and
front-end filters to be applied to each receiver,
if that makes sense for what you’re doing.
If you don’t have the second receiver, or it
is turned off, the two channels are still useful.
Tapping the audio effects (AFX) button brings
up a simulated stereo stream that can be a
constant phase shift between the audio channels or any of four delay intervals between the
two channels. It does add a feeling of depth
to the received audio.
The VFO tuning rate offers considerable
flexibility. The front panel RATE button
toggles the regular tuning steps between 10
and 50 Hz (20 Hz by menu selection). Another front panel button moves from regular
to either FINE (1 Hz per step) or COARSE.
Menu settings for COARSE steps vary per3J.
Hallas, W1ZR, “The Ten-Tec Omni-VII HF/
6 Meter Transceiver,” Product Review, QST,
Jul 2007, p 63.
Figure 4 — The rear panel of the K3/100 includes two antenna
connectors, provisions for a transverter, separate receive
antenna or preamp, and various accessory connections.
mode from 0.1, 0.5, 1 kHz through 5, 9 and
10 kHz. The faster settings apply to AM and
FM modes with 9 kHz intended for European
AM broadcasts on 9 kHz spaced channels.
Another menu item sets the steps per rotation
to 100, 200 or 400. I find the 200 step setting
just right, offering 200 Hz, 2 or 10 kHz per
revolution with the 10 Hz RATE and 1 kHz
COARSE setting. The FREQUENCY display
shows the appropriate digits for the resolution selected.
There are 100 memory locations available, selected using the VFO A knob. Ten of
these are selectable with a quick two-button
push and I have these set up for band selection instead of using the BAND up-down bar.
Once on a band, it is possible to have another
two-button sequence move you between your
favorite modes with associated filter and
other settings.
Those Roofing Filters
Many have wondered about the different
roofing filters and how they impact performance so they can decide which to order. In
addition to the 13 kHz filter for FM and 6 kHz
filter for AM and extended SSB, we tested
our unit with 2700 and 500 Hz five-pole and
2800, 1800 and 400 Hz eight-pole filters.
Each receiver is limited to five filters at a
time, and there’s a bit of menu setup involved
when you install or change them.
An FAQ on the Elecraft Web site goes on
to explain that the K3 uses hardware AGC
after the roofing filter and before the DSP.
Signals inside the roofing filter’s bandwidth
will desense the receiver if they exceed about
S9 + 25 dB, and changing to a 400-500 Hz
filter reduces blocking from signals 1 to
5 kHz away.
The ARRL Lab made a number of measurements with the different filters and the results
are shown in the accompanying sidebar.
CW Features
Elecraft’s roots are in the CW only, portable low power (QRP) transceiver market, so
it’s no surprise that there are many features
especially for the CW operator. Perhaps most
Figure 5 — Interior view of the
K3/100. The 100 W output stage
is shown in the center rear. The
subreceiver occupies the
L shaped enclosure filling the
front portion of the inside of
the radio. Removing the two
knurled nuts and three miniature
coax connections allows
the subreceiver to be easily
removed to add main receiver
roofing filters, for example.
notable is a zero-beat CW tuning indicator.
Push CWT and the upper end of the S-meter
bar on the display becomes a zero-center
tuning meter. It works well, even for surprisingly weak signals. Perhaps even better — if
CWT is on, pushing SPOT automatically zeros
the received signal in your passband. This is
important to take advantage of the razor sharp
selectivity provided. If the received signal is
not exactly centered in the passband, dropping the width to the tightest settings could
make the signal disappear.
An internal memory keyer is provided
with rear panel connections for paddles. A
rear KEY jack is also provided — both are a
convenient 1⁄4 inch size, by the way. I finally
have an easy way to hook up both sides of my
ancient Brown Brothers CTL model combination straight key and paddles. The straight key
is handy for trimming up the tune of my linear,
as well as for ARRL Straight Key Night.
Speaking of linear amplifiers, a menu
choice provides for RF output timing delay.
You can set the timing to accommodate the
switchover delay of your break-in capable
linear. Mine works flawlessly with full breakin. For those using contest software, a menu
selection can set the RS-232 computer connection control leads to key the transmitter
under command of the PC.
The K3 break-in switching is as smooth
and quick as any radio I’ve used. Major CW
controls, including KEYER SPEED, PITCH
and MONITOR LEVEL are front panel rotary
controls, as they should be on a serious CW
radio. The MONITOR LEVEL is independent
of the AF GAIN setting, for which my ears
are grateful.
SSB Features
For those who don’t like being con-
strained by the usual SSB filter bandwidth,
extended SSB (ESSB) is provided, currently
to a 4 kHz width. ESSB requires the optional
6 kHz filter. The K3 provides a single eight
band, ±16 dB/octave audio equalizer contour.
Having one setup for DX and contesting and
a separate setup for ragchewing would seem
like a beneficial addition. A similar, but
separate, equalizer is available for receive.
In this case one per mode might be handy.
Recent firmware has added a noise gate
feature to SSB transmit. This allows you
to set a threshold to eliminate background
noise — especially handy if you are using
compression, or have a noisy amplifier fan,
for example.
The VOX is among the best I’ve used. It
picks up before the first syllable is over, the
ANTIVOX is not fussy and the VOX HOLD delay
is front panel adjustable. A monitor function
is provided, the level setting sharing the front
panel CW MONITOR knob while in voice
modes. This is best used with headphones to
avoid acoustical feedback, but is very handy
for setting up the equalizer, gain, compression, noise gate and other transmit controls.
The front panel MIC connector is the
common round 8-pin type, wired almost to
the Kenwood standard. If you use an electret
mic, the bias connections need adjustment. In
addition, there is a rear panel 1⁄8 inch phone
MIC connector, as well as an 1⁄8 inch phone
LINE IN connector for sound card or other
external sources. The LINE IN GAIN can be
set independently of the MIC GAIN so you
can move between modes without having
to change your gain settings. Menu settings
determine which of the inputs is active.
There is also a rear panel PTT connector
so if you have a Heil headset, for example, it
and a companion foot switch can be plugged
From January 2009 QST © ARRL
The Elecraft K3 as a Contest Radio
How does the Elecraft K3 perform as a contest radio?
To find out, I used a K3 in two major contests in 2008: CQ
Worldwide WPX CW at the end of May and the IARU HF
World Championships in July. In WPX, I used the K3 as the
primary run radio in my SO2R (single operator, two radio)
contest station. In IARU, I used the K3 mostly for searching
and pouncing (S&P) for contacts on other bands while CQing with another radio on the main band. I also tested the
K3’s diversity reception capability in IARU, using the newlyreleased KRX3 subreceiver module.
Results in both contests were outstanding. As a run radio,
the K3’s receiver is the best I’ve used to date. The adjustable AGC action was smooth and allowed me to distinguish
between signals of different strengths in pileups. Thanks to
the K3’s 500 Hz and 200 Hz roofing filters, the AGC wasn’t
overwhelmed by the many strong signals up and down the
band, and there was no hint of IMD. The DSP selectivity was
useful down to 100 Hz without significant ringing. The ability
to store and retrieve passband settings, as well as return to a
baseline “normal” passband setting, was useful after making
changes to avoid temporary interference or to work stations
on the edge of the passband.
The K3’s DUAL PASSBAND feature establishes a narrow
passband inside a wider, attenuated passband. This lets you
hear stations outside the narrow passband, but without being distracted by strong adjacent stations. In practice, I found
the outer passband to be too wide for practical use on very
crowded bands — adjacent stations were just too loud. However, the DUAL PASSBAND feature has recently been enhanced
by Elecraft. Among other improvements, the outer bandwidth
directly into rear connectors without the
need of a special cable adapter. The K3 also
includes a true RF compressor with a front
panel control that works quite smoothly.
Digital Features
The K3 is very much a digital friendly transceiver. We mentioned the LINE IN connector
earlier, and there is also a LINE OUT connector.
Both directions provide transformer isolated
connectivity and have levels adjustable independently of those set for voice modes. The
RS-232 computer serial connection can be set
up to accept PTT (or CW keying) directly from
the RTS or DTR control lines without need for
an interface adapter. With these connections,
sound card modes require only a pair of 1⁄8 inch
phone cables and a serial connection. A USB
adapter is available from Elecraft if your PC
doesn’t have a serial port.
Special DSP filter settings enhance RTTY
or other frequency shift keying mode (FSK)
operation. Narrow filter bandwidths can be
established separately for the mark and space
frequencies, eliminating potential interference from signals in between the two. This
also improves reception signal-to-noise ratio
by reducing the noise bandwidth, compared
to the usual filter that passes both tones and
all that is between them.
AM and FM Features
The K3 provides for these modes as well.
AM reception is reasonable using the basic
From January 2009 QST © ARRL
can be adjusted. This is one of the best reasons to own a K3
— firmware updates over the Internet can address problems
and implement new features requested by customers.
Other rigs I’ve tried suffer from various shortcomings,
including signals slipping under the filter skirts, filter ringing,
AGC pumping, and inability to sort out calls in a pileup because of poor AGC action, IMD and too much circuit noise.
The K3 doesn’t suffer from these problems.
Diversity Reception
In IARU, I was able to evaluate the K3’s unique diversity
reception capabilities. Diversity reception allows you to listen
to two different antennas at the same time, one on the main
receiver and the other on the subreceiver. By using antennas
with different properties, such as horizontal or vertical polarization or different peak arrival angles, the combined effect
can overcome selective fading and other propagation variations more effectively than a single antenna or even a stack
of antennas at different heights. In addition, you can use
diversity reception to listen to multiple directions at the same
time without splitting transmit power.
The key to diversity reception is to use two identical receivers with their VFOs locked together. Many transceivers
offer a full-featured main receiver and a subreceiver with
reduced performance and capabilities, and most lack the
ability to lock the VFOs. The K3 is the only transceiver on the
market that offers two identical high-performance receivers
with VFOs that can be locked. In addition, each receiver can
accommodate up to five crystal roofing filters. Although some
interesting effects can be created by using different filters for
2.7 kHz roofing filter and tuning on one side
or the other as if it were SSB. If you are
serious about AM, though, you’ll want the
optional 6 kHz filter. It’s also required in order
to transmit AM. If you also have the 13 kHz
wide FM filter, it can also be used for higher
fidelity AM reception, but transmit is limited
to using the 6 kHz filter. For shortwave listening, you’ll also want the KBPF3 general
coverage receive band-pass filter module.
FM operation requires the optional FM
bandwidth roofing filter. If FM is enabled, the
K3 can be set for default repeater split options
on a band by band basis. Channels can be set
into memory, including CTCSS access tones.
I didn’t have an opportunity to try FM in my
K3, but it might be of interest to those with
local 6 or 10 meter repeaters.
Transverter Features
The K3 works best as a transverter
driver if the accessory KXV3 connection
panel is added. This unit not only provides
dedicated input and output connections for
a transverter, but also a port for a separate
receive-only antenna and a buffered IF output
for panadapter or other use.
We ran into an issue with our early production KXV3 when a reviewer attempted
to use the radio with a separate receive antenna located close to the transmit antenna.
Isolation in the KXV3 was insufficient to
prevent transmit RF from entering the K3
through the receive antenna port. Other users
reported this on the Elecraft e-mail list, and
it was promptly fixed in production in late
February 2008. There’s a modification kit
for those who have earlier units — see the
Elecraft Web site.
Not surprisingly, since Elecraft offers a
line of transverters, they have included all
the features needed for seamless transverter
operation. All you need to do is tell the configuration menu that you have a transverter,
what frequency (band bottom) it’s for, what
IF frequency you want (10 and 6 meters are
the most common, but you can select another
band if you need to), the maximum power
level you want to send to it, any frequency
calibration error in the transceiver and then
the correct transverter frequency shows up
as you advance the BAND button, just as
if it were built in! The K3 supports up to
nine transverters, each with potentially a
separate IF range and power level. If you
use Elecraft transverters, a special interface
connector makes sure the correct transverter
is engaged.
One Hardware Failure
The K3 has worked as advertised, or very
closely, but we did have a failure during testing. Following extensive audio output testing,
the speaker output completely disappeared.
Fortunately, the front and rear headphone
outputs continued to operate so the dynamic
testing could continue. The speaker output
amplifier ICs are on a DSP sub-board that was
diversity reception, it’s best to use filters with identical width
and specs in each receiver to avoid phasing problems.
To test diversity reception, I used a Y cable to connect my
580 foot northeast Beverage low noise receive antenna to the
K3’s RX ANT jack and the subreceiver’s AUX RF jack so I could
use the Beverage as either a receive-only antenna or a diversity antenna. I also modified my antenna switching system
so I could feed a number of different transmit antennas to the
Diversity reception takes some getting used to. Because
of the stereo effect and variation of signal strength on each
of the antennas, signals sometimes seem to “float” around
between your ears. But the ability to dig out weak signals
is impressive at times, and well-worth the slightly strange
audio. I found the combination of my two element 40 meter
Yagi and 40 meter four square vertical array to be particularly
effective. Here the difference in polarization and arrival angle
often overcame the effects of selective fading. I was able to
copy better through static crashes, too. Since my two element
beam has a 20 dB front-to-back ratio, I was able to periodically listen “off the back” of the beam by pointing the four
square to that direction. I had similar results when using the
Beverage and inverted V antennas on 160 and 80 meters. It
was often easier to copy weak signals, and nice to be able to
hear Caribbean stations on the inverted-V while still hearing
European stations loud and clear on the Beverage.
Operator category in the 2008 IARU contest, so I had an
­opportunity to evaluate the K3 as an IF receiver for the
LP-PAN panadapter.A My setup also used PowerSDR-IF
software and LP-Bridge software to link PowerSDR to the
K3. For full details of this ­powerful K3 accessory, see
Setting up CW Skimmer can be challenging, a subject
that’s beyond the scope of this sidebar. Suffice it to say that
the best approach is to use CW Skimmer with a dedicated
wide-band receiver and a dedicated antenna. Not having
those items at my disposal, the K3 had to do double duty
as both a CW Skimmer receiver and an S&P transceiver.
Technical limitations in CW Skimmer didn’t allow me to do
these things at the same time. So, I had to let CW Skimmer
run for a few minutes to decode signals in the passband
and load up the contest logger’s bandmap with call signs
and frequencies. Then I shut it off so I could grab and work
the stations spotted on the bandmap. Although somewhat
cumbersome, this technique netted enough second radio
multipliers and contacts for me to place well in the contest.
Bottom line: The K3 performed admirably as an S&P and
CW Skimmer radio.
The K3’s small size can be deceiving. Inside the diminutive package is a world-class, state-of-the-art contest radio
with a pair of the best receivers I’ve used. — Dick Green,
LP-PAN and CW Skimmer
When putting in a full-time, serious contesting effort, I
always compete in the Single Operator category. A one-time
ruling allowed CW Skimmer software to be used in the Single
quickly replaced by Elecraft and operation
was back to normal.
Firmware and Support
I have grouped these together, because
with Elecraft they go hand in hand. With an
SDR radio such as the K3, each firmware
reload can provide almost a whole new radio,
within the constraints of the front panel controls and displays. Thus, most support issues
of an architecture or design implementation
nature are resolvable in firmware.
Elecraft has been, in my opinion, remarkably responsive in this area. The company
principals regularly participate in, and even
moderate, the e-mail discussion list (see
mailman.qth.net/mailman/listinfo/elecraft). Reported bugs are usually resolved
within a day or two by the posting of new
firmware. Feature changes or different
operating options are discussed by a lively
group with participation from the principal
developers. If a consensus emerges, the next
beta version will include the feature. If there
is no clear consensus, the feature may end up
a menu option.
A recent example was the use of the
A>B button. Originally a touch of the button
would cause the frequency, mode, bandwidth
and other settings to be transferred between
VFO A and VFO B. It was changed in a subsequent release to transfer just the frequency
to VFO B on the first tap, then transfer the
Skimmer (www.dxatlas.com) simultaneously decodes all CW
signals within the receiver passband, and its use has been the subject
of much discussion within the contest community. The latest rules for
most major contests indicate that it can be used only in those categories that allow use of spotting networks and other assistance.
other parameters on the second. This seems
a bit esoteric, but the respectful discussion
raised good reasons for both approaches under different scenarios. The review, including
all testing, was conducted using firmware
version 2.46, the current production code
during the review process.
Elecraft has done an excellent job with K3
documentation. Check it out yourself — it’s
all available on their Web site, including assembly manuals for the base K3 and all the
options as well as the operating manual. The
one problem is that a manual is frozen in time
with only the changes that have happened up
until publication.
There are a number of ways to handle a
dynamic environment such as the K3 with
its frequent firmware releases. Elecraft has
chosen to issue release notes with each software revision that describe all the operational
changes that have been incorporated. I have
a loose leaf binder with the latest manual
and all the release notes issued since the
manual revision. This is a viable way to
do it, but I’d prefer manual change pages
with each release so the manual index and
table of contents would get you to the latest
information. Of course there are those who
get their K3 and are thrilled with what it
does and how it does it and never upgrade
their software — that’s another viable option.
After all, there was a time when all radios
worked that way!
More to Come
Two additional options for the K3 have
been announced, but were not available in
time for this review. The KDVR3 voice recorder provides over 6 minutes of nonvolatile
voice storage. This is divided between eight
one button user recorded message buffers, recording signals off-the-air for later playback
or even for use as keypress annunciators. The
one-button buffers can be used for calling
CQ or contest exchanges or even to record
received audio.
The K3 receiver was designed with optimized dynamic range as its primary goal. As
noted, it has achieved that nicely — thank
you very much. Unfortunately, it is difficult to
obtain highest sensitivity and highest dynamic range in the same radio. The sensitivity is
fine for HF, where external noise is generally
the limiting factor, but for some K3 owners
additional sensitivity is needed on 6 meters.
The optional PR6 GaAs FET low noise
6 meter preamp can be connected to the
KXV3 interface panel so that the transverter
connections feed through when it’s not in
use. It promises a typical noise figure of
0.5 dB.
Manufacturer: Elecraft, PO Box 69,
Aptos, CA 95001; tel 831-662-8345;
From January 2009 QST © ARRL
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