Western Digital "Livewire" ethernet modem
PLEASE NOTE THE FOLLOWING:
I DO NOT own one of these modems! The one
that I tested came across the workbench and I happened to have enough
time to analyze the RF spectrum occupied by this modem.
I DO NOT know how well these work or "how far"
I DO NOT know for certain if they will or will not
bother amateur radio operations.
I DO NOT know if transmitting on amateur, CB or
other frequencies will bother these modems.
I DO NOT know for certain if they will or will not
bother other radio (e.g. commercial AM/FM broadcast, TV, or CB)
I DO NOT know for certain if they will bother
I am an Amateur (Ham) radio operator and my opinions are biased,
so you should take that into account!
The opinions expressed on this page are my own - so there!
When used as-designed, these modems - which connect via the
domestic mains power - are quite safe to use from
the perspective of the average user. If, however, you attempt to
modify or measure their characteristics, you should be very careful to
prevent shock/fire/other hazards!
I cannot take any responsibility for damage, injury or
interference that might result from the use of this or similar types of
Again, this page only analyzes the frequency
utilization of these modems. Whether or not they are likely to
cause interference in your situation would have to be determined by your
It should be pointed out that devices such as these are covered under
FCC Part 15. If one examines the literature accompanying devices
such as these that have the potential to cause interference to other
radio/wireless devices - or even your TV, DVR or computer - you'll find
a notice included that is worded something like this:
This device complies with part 15 of the FCC Rules.
subject to the following two conditions:
(1) This device may not cause
harmful interference, and
(2) this device must accept any interference
received, including interference that may cause undesired operation.
What this means is that anyone who operates such a device, by using it,
agreed to be responsible when it comes to any
interference that the device under question causes - that is, if
someone complains that said device causes interference to them, it is
incumbent on the owner of that device to mitigate that
interference - even if it means that you have to stop using it!
means that if radio operation causes the device to not
work properly - such as when a Ham operator transmits - that the user
of that device has no legal recourse when it comes to stopping such
operation as this agreement also stipulates that they are using it at
their own risk.
The simple fact is that many devices are just susceptible to being
interfered with by RF signals: If you have a GSM telephone (like
an IPhone (tm), Blackberry (tm), etc.) you may have noticed that if you
are using it you'll sometimes hear your stereo, TV or computer speakers
buzz when you receive or send a call, text, data, or browse the web -
and this buzzing is a result of circuits in those devices
unintentionally picking up radio frequency (wireless) signals.
While it's true that devices could be designed to resist such
interference (stronger rules in some countries required a degree of
resistance to this effect - but not necessarily so in the U.S.)
so would add a few cents or dollars to the device, so it isn't done.
Therefore, someone using a device such as this is obliged to not
interfere with other users of the spectrum - even if the device is
operating as designed!
Purpose of this page:
Recently, one of these modems - Western Digital "Livewire" -
crossed my path: An acquaintance
of mine bought one of them and a co-worker and I were curious about
of operation, so, during a bit of "off" time at
work, we placed it on the bench, coupled it to a spectrum analyzer and
looked at its RF utilization.
A little about "BPL" - or "Broadband over powerline"
One of the reasons why we were curious has to do with the recent
kerfuffle about "BPL" - that is "Broadband
Powerline" communications. The proposal was
that, using existing wires that ubiquitously connect our lives - namely
powerlines - RF signals could be conducted across those same lines that
would allow broadband data connectivity with a relatively minimum of
outlay and added infrastructure. To this end, a number of pilot
projects and some full-time services were implemented over the years to
demonstrate and bring to fruition (possible) commercial applications of
The proponents of the system had stipulated that the conductors of
power were adequately efficient for this task and that minimal
radiation of the RF (Radio Frequency) signals would occur from these
powerlines. This last point is an important one as that property
is necessary for such a system to work effectively and the conducting
wires not radiate signals into the air (as an antenna
might) and cause interference to other services - or itself by
cross-coupling of one "branch" of BPL service/customers into another.
For the most part the proponents are right: Very little of the
signal is actually radiated from the lines along any given segment -
but how much is too
much, and if a little bit of power is radiated from each segment of
powerline, how much is radiated over the entire run when you add it all
Since these same powerline literally connect us together, they go
everywhere and there is the real possibility that such signals
conducting the data will interfere with existing services: After
all, there's no real way to "route" the RF energy - except by virtue of
the where the powerlines conducting this RF energy just happen to run
unless, of course, some sort of filtering was installed on the
powerlines themselves. This latter point is an unlikely prospect
as suitable filters, to be effective, would likely be quite large and
expensive were they to be placed on feeder lines and their installation
would require an interruption in power to customers being served on
those lines: Their use by power companies or their internet
partners seemed unlikely!
In addition to these RF signals being conducted, there was the
possibility that the overhead power wires on which these RF data
signals would be imposed would, in fact, act like antennas.
Particularly concerned the possibility of this happening were Amateur
Radio Operators ("Hams") and shortwave listeners who use portions of
the "HF" radio spectrum from 1.8-54 MHz (among other places) - the same
general frequency range expected to be used by BPL operations.
Also concerned were broadcasters - AM, FM and TV - who worried that
customers' signals may be degraded by the presence of these "other"
Figure 1: The modem and its
testbed. Top: The modem itself Center: The modem, signal coupler, and spectrum analyzer
used. Bottom: The makeshift "Current Transformer" used to
couple the RF from the power cord. Click on an image for a larger version.
This concern sparked a debate among the amateur radio groups as well as
some concern among government and commercial users of the HF radio
spectrum that frequency ranges over which BPL operated would
essentially become unusable. On the side of the proponents,
statements made by the FCC indicated great optimism that the technology
was feasible and would not result in significant disruption to users of
the "shared" spectrum.
Amateur radio operators, on the other hand, took it
upon themselves to review the literature and make their own in-field
measurements, dragging radio gear and test equipment into communities
in which BPL systems had been installed. To the dismay of the
amateur radio operators, their worst fears were justified when it was
observed that moderate to extreme interference was observed and that
some of the recommendations made by the technical arm of the FCC were
seemingly dismissed in favor of moving forward with deployment.
Here are a number of videos related to the "Hams-versus-BPL" debate:
HF - A Primer. (YouTube video) - In-field
demonstration of BPL and interference in North Carolina.
As can be seen from the above videos, there is some understandable
concern that systems that use standard wiring - either power
distribution or in-home wiring - could cause interference to shortwave
(and other) communications. Again, being an Amateur Radio operator, I tend to be concerned about
the use of such systems that have the strong potential toward causing
interference to existing services - even when used in the manner in
which they were intended to be operated!
The difference between "BPL" and the type of device
At this point it is worth mentioning that there is a
difference between BPL and the devices intended for providing in-home
BPL is intended to provide connectivity across the community,
using the powerlines as a conduit for the broadband signals.
The device described here is intended only to
provide connectivity within a single dwelling and is not
intended to provide signal outside the person's own house wiring.
What these devices share in common are the fact that they both
mains to conduct the radio signals used to carry the data and their
potential to cause interference to users of the HF spectrum.
The Western Digital "Livewire" device.
Refer to the pictures on the right, in Figure 1.
This is a consumer device that is intended to be used within the home
to provide connectivity by using the in-house wiring to conduct RF
signals amongst computers. Based on what was already known about
potential for such devices to cause interference, we decided to put it
on a spectrum analyzer to see what it's spectrum looked like.
Again, these are observations made on what signals the modem
produced. There was no attempt to provide an analysis of actual,
in-use operation and its impacts on HF operation.
The spectrum analyzer readings were taken with the modem in its
"idle" state. In that mode, the received signals are periodic
pulses, not unlike the "popping" one might hear on a radio from a noisy
spark plug on a gasoline engine. When higher throughput is called
for the pulsing turns to buzzing or hissing - the rate and sound
varying with the bandwidth/usage of the link.
The test setup:
The test setup was very simple. We had, on hand, a 3-way
power tap (the orange thing) that had been modified to allow the use of
a clamp-on ammeter to measure current consumed by a device plugged into
it. These modifications were very simple: Simply cut away
the outer jacket of the power tap and expose the three individual wires
(each being independently insulated) so that current in each of the
three leads - Hot, Neutral and Ground (Black, White and Green,
respectively) could be measured. Due to the very nature of
current flow and magnetics, simply clamping a meter on the entire cord
and surrounding all three conductors would not yield usable results as
the magnetic fields would cancel out - hence the requirement that each
wire be individually accessible.
To couple the HF (High Frequency) energy transmitted by the modem into
the power line several turns of wire were wound around the black (Hot)
conductor to act as a very simple current transformer - with the wire
passing through it acting as the primary. The two ends of this
wrapped wire were terminated in a 15 ohm resistor (this low value being
used to minimize the effects of stray inductances on the pickup) and
then this was conducted, via coaxial cable, to the spectrum
analyzer. In this way the RF signals could be picked up while
detecting a minimum of other signals - except, of course, those that
might also be on the powerline itself.
Figure 2 (below) shows the initial plots of the occupied
spectrum of the modem.
Figure 2: Wide-bandwidth
of the spectrum occupied by this modem. Top Left: 0-30 MHz plot. Top Right: 0-10
plot Bottom Left: 10-20 MHz plot
Bottom Right: 20-30 MHz plot. Click on an image for a larger version.
We were both surprised and pleased to see that there were many "holes"
in the spectrum occupied by this devices. Closer analysis
indicated that these holes aligned nicely with the HF amateur bands and
the AM Broadcast band. Except for these holes, this modem
produced spectral energy over the frequency range from just above 2 MHz
to just below 28 MHz.
The "noise floor" in the analyzer plots (above) is generally that
of the modem itself. When the modem was powered down, the noise
floor (of the analyzer and pickup coil) was at least 10dB below that of
the modem - with the exception of the AM broadcast band carriers that
can be seen at the left (low frequency) edge of the "0-30 MHz" and
"0-10 MHz" plots, above.
These plots were taken using the "Max Hold" feature of the
analyzer and allowed to integrate over time. In doing so, the
noise and peak levels are somewhat exaggerated, but still in relative
proportion to readings taken in which levels of individual data bursts
the noise floor were measured.
The amplitude discontinuity across the broad band (that is, the
"steps" upward in signal level as frequency increased) may be due to
the frequency response of our simple setup or they may be due
to actual power level differences within the modem: We just don't
Based on these results we decided to "zoom in" using the analyzer and
see, exactly, how wide and deep these "notches" were - an indication as
to how effective they may be in preventing interference to amateur, HF
communications. To do this, individual plots were taken of each
of the HF amateur bands.
It should be pointed out that these "notches" aren't due to filtering
within the device, but just that the device has been programmed NOT
to use certain frequency ranges.
Figure 3: Plots centered on
the 160 and 80 meter amateur bands
160 and 80 meters:
Figure 3 shows a spectrum +/-500 kHz (a total of 1 MHz span)
about the center of the 160 and 80 meter amateur bands.
As can be seen from the plots, the energy is about 28dB down at the
edges of each amateur band - a significant reduction. Into the AM
broadcast band, the signals drop off dramatically: The slight
"peaks" are due to leakage of nearby AM stations into the power cord of
the test setup.
Figure 4: Plots of the 60 and
40 meter amateur bands
60 and 40 meters:
Figure 4 shows 1 MHz wide spectrum plots of the "60" meter band
and centered on the 40 meter band.
We were surprised to see a "notch" in the general area of the "60
meter" amateur band. At the time of writing, this isn't an
"amateur band" per-se, but a number of individual channels on which
restricted amateur radio operations are permitted in the 5.2-5.4 MHz
area: The exact frequencies of operate vary depending on the
country and are subject to change.
The 40 meter band is also "notched" out to the tune of 30-33dB at the
Figure 5: Plots centered on
the 30 and 20 meter amateur bands
30 and 20 meters:
Figure 5 shows 1 MHz wide spectrum plots of the 30 and 20 meter
The measured "notch depth" on 30 meters - a rather narrow (50 kHz wide)
band just above 10 MHz was not as deep, but still over 25dB. At
the edges of the 20 meter band notch depth was about 27dB, but well
over 30dB in the center.
Figure 6: Plots centered on
the 17 and 15 meter amateur bands
17 and 15 meters:
Figure 6 shows 1 MHz wide spectrum plots of the 17 and 15 meter
17 meters - like 30 meters - is a rather narrow band and the depth of
the "notches" at the edges weren't as deep - but still over 25dB.
As with 20 meters, the notches at the edges of 15 meters were about
27dB deep and well over 30 in the center of the bands.
Figure 7: Plots showing the
12 and 10 meter amateur bands
12 and 10 meters:
Figure 7 shows a 1 MHz wide spectrum plots of the 12 and another
plot spanning from 27 to 30 MHz.
The results on 12 meters were very similar to those on the other two
WARC bands (e.g. 30 and 17 meters) with slightly lower "notch" depth
owing to the relative narrowness of the band - but still over 27dB
within the band itself.
The final plot shows a 3 MHz wide swath from 27 to 30 MHz, encompassing
much of the CB radio frequencies and all of the 10 meter amateur
band. At the very bottom edge of the 10 meter amateur band the
depth of the "notch" is only about 25dB, but it approaches 40dB by the
time one reaches the upper edge.
Above 30 MHz there is very little energy: It would appear that
the highest frequency being used would be just below 28 MHz and by the
time one gets above 50 MHz or so, residual energy from this device was
unmeasurable with our simple setup.
We were pleased to note that the whoever designed this modem was
conscientious enough to "notch" out the HF amateur bands and to not
utilize frequencies in the AM broadcast band.
If you are an avid shortwave listener - and either you or a
neighbor has one of these modems in the house - you may be in trouble!
If you are a CBer - and either you or a neighbor has one of these
modems in the house - you may also be in trouble!
If you are an amateur radio operator listening only within one of
the HF amateur bands and you have one of these in your house, you will
likely hear it: Whether or not it will prove to be disastrous to
your reception capabilities in anyone's guess and likely depends
strongly on how the house's wiring conducts and radiates these signals.
If you are an amateur radio operator listening only within one of
HF amateur bands and one of your neighbors has one of these in their
house, you may hear it: Again, whether or not it will
prove to be disastrous to your
reception capabilities in anyone's guess and likely depends strongly on
how the house's wiring conducts and radiates these signals.
I would not want to have one of these in my house and I would
rather that none of the neighbors did, either!
With the proliferation of wireless devices operated in the 2.4
GHz and higher frequencies, it is expected that these sorts of devices
are not likely to proliferate highly - at least in the
U.S. - as they
simply aren't quite as convenient as "Wi-Fi": To use them, one
has to take up another
plug one of these devices in and the ethernet cable must be plugged
It is unknown if all versions of this modem have "notches" in the
HF amateur bands. It is possible that different revisions aren't
so-programmed. Any firmware/software revision level information
of this particular modem is unknown.
It is unknown if other brands/models of similar modems have
"notches" in the HF amateur bands.
The part number of the modem tested was: WDBABY000NBK-NESN.
Your mileage may vary!
Any comments or questions? Send an email
- but please remember that I really can't answer any questions
about if these will cause interference as I don't actually own these
devices, nor have I used them.