The WiFi transmitter in my Actiontec GT701-WG produced interference over
much of the HF spectrum and completely obliterates the 17 meter band.
With my HF receiver in AM mode, looking at the received audio with a
spectrum analyzer, I see peaks at 60Hz and 120Hz. The router and WiFi
portion work just fine.

That's distinctly puzzing, from a frequency point of view, since the
WiFi frequency is far above HF, and the 802.11 protocol tends to use a
beaconing / timeslicing which isn't tied to the powerline frequency
cycle.

Anybody ever run into a problem like this and found a solution to it?

Consumer-grade networking gear is notorious for generating QRM. I
haven't seen this specific symptom before.

I can eliminate the noise by disabling the radio in the router, but a
real fix would be preferable.

I could imagine several paths for the interference:

- The presence of 60 and 120 Hz sideband spacing suggests that it may
be power-supply related. Possibly, the enabling of the radio is
raising the WAP/router's current consumption beyond what the "wall
wart" is capable of delivering. If the DC voltage supplied by to
the router were sagging 120 times a second, it might generate all
sorts of interesting QRM... and this might be leaking out of the
cabinet directly, or coming back out along the power cable. Or,
perhaps, a switching-supply wall wart might be emitting QRM
directly under conditions of high (but acceptable) current load.

- There might be QRM RF coming out to the WiFi antenna... but that's
a pretty good approximation of an infintesimally-short
dipole/monopole at HF and wouldn't radiate efficiently.

- The QRM might be coming from the radio itself, but leaking back out
through other paths... onto the Ethernet cables or the power wiring.

I'd tend to suspect the power supply, and QRM leakage back out into
your household AC wiring... that'd be a much more efficient path than
emission out of the WiFi antenna.

As to specific examples: I've chased down QRM problems involving two
different pieces of consumer Ethernet / wireless gear.

One was a buzzy QRM which wandered around the whole 2-meter band, and
was bad enough to get in on the squelch tails of at least two
repeaters located miles away. The cause was a 10/100-megabit hub
which was "singing" loudly - I believe it was probably a harmonic of
one of its on-board clock oscillators. The QRM was apparently getting
out into the external power wires and external Ethernet cables
(common-mode, I assume) and was being re-radiated efficiently.
Replacing the switch with one of another brand fixed the problem.

The second was a a set of closely-spaced (some kHz apart) spurs
throughout the 2-meter band, strong enough to open the squelch on an
HT or scanner. These were coming from the switching DC-to-DC
converter inside a wirelss router/switch (one of the Netgear grey-
plastic varieties). They seem to have been radiating directly out
from the PC board, as they were strongest with the probe closest to
the chassis, and did not appear to be leaking out through the DC
cable to the wall wart. The router had some ferrite beads and cap
bypassing for the DC input. Replacing the WAP/router with a different
model fixed the problem.

If your router is of a fairly recent vintage, it was probably supplied
with a switching-type DC supply... I think a lot of the cheaper ones
can be prone to be HF-noisy. You might want to consider finding
an old linear-type (transformer/rectifier/caps) supply with the same
output voltage and equal or better current capacity, and see if that
makes the problem go away.

Other possible technical fixes: wrap the DC power cord through a
clamp-on ferrite a few times, as close to the router as possible;
figure out how to construct a high-pass filter for the router's
antenna connection which will pass signals above 2 gig and block
signals below that.

If all else fails, replace the router with a different brand.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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