ARRL SOTABEAMS User manual

www.arrl.org QST March 2020 7
Reviewed by Paul Danzer, N1II
[email protected]
The Wolfwave Advanced Audio Processor from
SOTABEAMS can add selectivity to an existing
receiver or transceiver, and it offers a number of
other audio processing features as well. It connects
to the headphone jack or speaker output and pro-
vides processed audio that can be used with head-
phones or a speaker.
Overview
The block diagram for the Wolfwave is simple —
audio is fed to an analog-to-digital (A/D) converter,
and then it goes to a microprocessor. The processed
SOTABEAMS Wolfwave Audio
Processor
Bottom Line
The Wolfwave Advanced Audio Processor
oers a number of ways to add lters, noise
reduction, and other features to receivers
without those amenities.

8 March 2020 QST www.arrl.org
signal then goes to a digital-to-analog (D/A) con-
verter and then to an audio amplifier connected to
the output jacks. The 4 × 3 × 1 inch package is pow-
ered by either a USB cable (cable included, without
USB power supply) or an external 5.5 to 18 V dc
supply. Current draw is approximately 60 mA. We
used a 12 V dc wall cube supply.
The Wolfwave is controlled by firmware, which can
be updated online using the USB cable. If the USB
cable is used to power the unit, the 5 V available in a
standard USB connection is fine for headphone use,
but it will provide lower speaker output than the 1 W
available when using an external power supply of 7 V
or more.
The right side panel of the enclosure has a 3.5-mil-
limeter stereo headphone jack and a 3.5-millimeter
speaker jack, along with the 2.1-millimeter coaxial dc
power receptacle (center pin positive). The left side
has the 3.5-millimeter stereo audio input jack and a
micro-USB connector. There is also a pushbutton
labeled
FIRMWARE for use during the update process.
One important word of caution — neither side of the
speaker can be grounded. The audio amplifier has
both output leads floating, and grounding one of
them may result in damage to the amplifier. This is
important to note if you are using a matching
speaker to an older transceiver where one speaker
lead is typically grounded to the metal enclosure.
Received audio spectrum and menu commands are
shown on a monochrome front-panel display that
measures approximately 11⁄8× 11⁄16 inches. A two-
color LED is mounted just to the upper left of the dis-
play and tells you if the audio input is high enough
(green) or too much (red). If the LED shows red,
back off the transceiver volume control and use the
volume control on the Wolfwave to set a comfortable
listening level. There is no power on/off switch, so
you will have to control this function externally.
There are three pushbuttons on the front panel.
MENU picks the general function you want to select or
adjust.
MODE lets you adjust the selected function
and access submenus if available. HELP brings up
context sensitive information, just as a right click
does on many PC applications.
On the bottom of the panel are the audio
VOLUME
control and one labeled MULTI-USE . Pressing
MULTI-USE is the same as pressing the MODE button.
Rotating it helps select operating mode and menu
values.
Using the Controls
I found that there was a bit of a learning curve to be
able to rapidly make selections and adjustments
using the menus and submenus. The Wolfwave unit
has repetitive selection patterns, so with practice,
these selections can be made quickly and accurately.
The initial display shows an audio spectrum (100 –
2,700 Hz) with a vertical dotted line in the center rep-
resenting the filter center frequency. The default is
that the band-pass filter is enabled, bandwidth is
2,400 Hz, and the center frequency is 1,500 Hz. To
show the general pattern of operation, let’s set up a
CW filter:
Rotating MULTI-USE (we’ll just call it MULTI ) changes
the filter bandwidth in the range of 50 Hz to 5,000 Hz
in steps of 10 Hz to 100 Hz depending on bandwidth.
At settings higher than 2,400 Hz, the spectrum dis-
play widens to 100 – 5,000 Hz. You can adjust the
width at any time.
Press MULTI and you will see CENTRE 1500 Hz (the
default center frequency). Adjust the center fre-
quency by rotating MULTI until it matches your pre-
ferred CW tone (I like 750 or 800 Hz). When you
adjust the center frequency below 1,175 Hz, the
spectrum display changes to 100 – 1,400 Hz.
Figure 7 shows a 600 Hz filter.You can adjust the
filter parameters every time you turn the unit on,
store your favorite settings, or select from several
preconfigured filters.
To access and adjust other Wolfwave features, the
general pattern is:
Press MENU to bring up a list of functions. Scroll
through this menu by rotating the MULTI control and
then press the
MULTI control to turn a function on and
adjust it. As an example, select NOISE REDUCTION ,
and a long press of MULTI will turn it on and display a
submenu with several options (including an
ADVANCED submenu with further options).
Figure 7 — The
Wolfwave set up
for a 600 Hz CW
fi lter with a center
frequency of 650
Hz.

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Rotate MULTI to highlight the desired parameter,
press MULTI to select the parameter, and again rotate
MULTI to adjust the setting.
Within each submenu, highlight the top line and
press MULTI to go back to the previous menu.
Within the menu system, pressing
MULTI and
pressing MODE usually have the same effect.
Pressing
MENU brings you back to the top-level filter
display without having to back out through multiple
menu layers.
Testing the Modes and Features
Bypass Function
A long press of the HELP button turns off the pro-
cessing functions. The label BYP will appear in the
lower left corner. A second press turns processing
back on.
Band-pass Filter
On-the-air testing showed the filter was very sharp
and as good as I wanted — as long as the LED on
the panel showed green. In addition to experimenting
with various SSB bandwidths, I tuned in a strong AM
broadcast carrier (S-9 plus) to be just inside the filter
passband. Then I slowly turned the transceiver VFO
knob to move the carrier out of the filter passband.
The carrier quickly dropped to just about S-0. With
just the tiniest change in transceiver tuning I could
manage, the carrier switched between these two
values — S-9 and annoying, to S-0 and barely
audible.
The Wolfwave offers 14 memories to store band-
pass filter settings. Four are preset — wide/narrow
for CW and data, and wide/narrow for SSB. The rest
are open for your selections, and you can designate
a default power-on setting.
A recent firmware addition is
BANDSTOP FILTERING ,
which allows the user to set up to 10 notches within
the passband. The center frequency and width of
each notch is adjustable, and the instructions sug-
gest 100 Hz as the minimum usable width. This
might be helpful to reduce unwanted signals within
the passband, low-frequency hum, high-frequency
hiss, or other irritants. When
BANDSTOP FILTERING is
enabled, any programmed notches are shown in the
BANDSTOP FILTERING display
Noise Reduction and Tone Reduction
I tested the NOISE REDUCTION function on 75 meters
during July, with typical high summer noise levels.
Coarse (5% steps) and fine (1% steps) adjustments
are available (see Figure 8). I started with the noise
reduction level at 50% while listening to my local club
net one evening. That level brought minimal improve-
ment. As I increased the setting toward 90%, the
noise went down, but the digital artifacts increased
(the underwater effect often heard with noise reduc-
tion systems). Weaker stations, which I could not
really hear in the noise, were reduced to clipped
snippets of sound. However, very strong stations
became much more readable. At around 75%, the
noise was reduced — but not to zero — and the
moderately strong stations were easily understand-
able. For quieter band conditions, settings around
30% reduce the background noise without too many
digital effects.
A submode of
NOISE REDUCTION is TONE REDUCTION ,
where the Wolfwave automatically identifies and
notches a steady tone. The NOISE REDUCTION mode
must be on for TONE REDUCTION to work. I tried this
function with AM broadcast carriers ranging from S-2
to well over S-9, and the tone was suppressed effec-
tively. Some fuzziness was introduced when the tone
was next to the edge of a sideband signal, but that is
to be expected.
Hearing Loss Correction
The manufacturer describes this function as applying
a gain curve that varies with frequency according to
the international standard ISO 7029 (www.iso.org/
standard/42916.html). From the main menu, select
HEARING LOSS COMP , and then your gender and age.
I use hearing aids, so I was very interested in this
mode. The instructions also note that if you do use
hearing aids, this compensation will not replace the
hearing aids. Generally speaking,
HEARING LOSS
COMP adds gain at higher audio frequencies. I
removed my hearing aids and set the function for my
gender and age. On CW, as expected, I heard no
obvious difference because the tone of the CW note
Figure 8 — Setting
the Wolfwave noise
reduction features.

10 March 2020 QST www.arrl.org
was not high (around 800 Hz). Similarly, I didn’t hear
a noticeable difference while listening on SSB with a
filter bandwidth set to 2,300 Hz.
I set the upper limit of the filter bandwidth to 5,000 Hz
and tuned in some music on a shortwave broadcast.
There was definitely a difference in the high frequen-
cies of the broadcast transmission, but because the
bandwidth was limited to 5,000 Hz, I didn’t hear a big
difference. While this mode appears to work, I didn’t
find it too useful for typical ham radio modes, which
have limited audio bandwidth.
More useful for some operators is the left-right bal-
ance control included in a recent firmware update.
Accessed from the
OUTPUT SETTINGS menu, this fea-
ture allows increasing the audio level in one ear or
the other in 1⁄2dB steps to compensate for differ-
ences in hearing.
Morse Code Decoder
Decoded text appears on the left side of the display
and a small audio spectrum scope on the right (see
Figure 9). The received signal to be decoded must
be centered in the spectrum scope.You can do that
by tuning your receiver to the correct pitch, or by
turning the
MULTI knob to match the Wolfwave to the
received pitch.
The Wolfwave automatically adjusts to the received
CW speed. The default setting allows CW speeds
from 5 to 40 WPM, but you can change the limits
from 0 to 100 WPM. The detection threshold can be
changed as well, which helps with false decodes
from noise.
I found the decoder to be very accepting of off-fre-
quency tuning — the pitch just has to be close to the
incoming signal. In addition to showing decoded text,
dots and dashes are shown at the bottom of the
screen and the measured code speed in words per
minute on the top left corner. If the band is noisy, try
raising the decoder threshold from its factory setting
of 3 dB to perhaps 8 or 10 dB.
CW Regen
CW regeneration is a function that I have not seen
for a long time. Many years ago, the National
Company included a function called Select-O-Jet in
several of its receivers. The circuit gave positive feed-
back on a selected frequency, and in the presence of
noise or other signals, the selected tones would be
boosted by the function.
In the Wolfwave, this experimental function detects
the dits and dahs in the received signal and regener-
ates the CW signal with a clean sine wave and no
noise. The CW tone to be regenerated must be in the
center of the passband, and the trigger level point
can be adjusted from 1 to 30 dB.The output (regen-
erated) tone can be set to be identical to the input
CW tone or offset from it. With a stereo headset, you
can listen to the received signal in one ear and the
regenerated CW tone in the other.
For the regenerator to work, I had to carefully set the
band-pass center frequency to the CW tone I use,
and to carefully limit the input signal to the green
LED range.The CW regenerator works well, but
tuning is critical. Any attempt to change the receiver
frequency by a tiny amount almost always resulted in
loss of copy, requiring shutting the regenerator off
and resetting the receive frequency.
Audio Test Generator
Under UTILITIES on the main menu, there is a selec-
tion to generate tones.Turning this on brings up an
audio generator with the output selections of sine
wave, triangle wave, square wave, and two-tone.
Each of these can be set to a selected amplitude and
frequency.
Support and Firmware Updates
The Wolfwave package does not include a printed
manual, but detailed information about setup and
operation may be found on the SOTABEAMS web-
site, as well as a website dedicated to this product
(www.wolfwave.co.uk). In addition to written
instructions, there are tutorials and links to helpful
videos.
SOTABEAMS offers accessories and replacement
cables for the Wolfwave. One that may be useful is
an audio ground loop isolator, which can reduce or
eliminate hum from ground loops. This isolator plugs
in between your transceiver and the filter, breaking
the ground loop.
Figure 9 — The
Wolfwave Morse
decoder screen.

www.arrl.org QST March 2020 11
Firmware updates may be downloaded, along with
Windows software and drivers needed for the pro-
cess. The Wolfwave website offers well-illustrated,
step-by-step instructions, as well as a video demon-
strating the update process. New firmware with
added features was released several times during
the review period, so it’s a good idea to check peri-
odically for updates.
Manufacturer: SOTABEAMS, Macclesfield, United
Kingdom; www.sotabeams.co.uk or www.
wolfwave.co.uk. Distributed in the US and Canada
by DX Engineering, 1200 Southeast Ave., Tallmadge,
OH 44278; www.dxengineering.com. Price:
$275.99.