I just moved to an apartment and wanted to keep my radio in the bathroom, same as I did in the last place I lived.
Only problem with this place is that the main electrical drop to the building is right outside my bathroom wall, interfering with FM/AM reception.
Is there anything I can do to alleviate this - putting a noise filter on the radio power cord, etc??
Right at the frequency of an AM I've been listening to for years, is a loud combination buzz/screeching sound.
It happens only to radios brought into this bathroom. Lots of static on FM, intermittent
multiplex(stereo for the young uns!) and loud static and that buzzy-shriek right below
80 on the standard dial(AM).
Once the boombox is moved somewhere else in the apt, it performs like a normal set.
This is (an example of) what I can see in the upper LH corner of my bathroom window:
A big honkin one, twice the size of a residential service! And the closer a radio set gets
to that thing, the worse it buzzes
With Radio reception, you can have architectural interference in a building or a residence
for a myriad of different reasons. Here, you have electrical power interference as well as
other metal (including aluminum) which inhibit radio waves from travel through it. If you
have a table radio or a portable, try moving the device closer to a window or area with open
air. Since you moved in and the place is new, I take a portable radio (an FM radio) from a
cell phone or bike radio and walk around to find out where the best reception is. This is
a trial and error approach. I then due this for AM and see if and where the best reception is
for AM and FM, what direction the antenna is pointed, how far away, etc...
I do this to find the best range within the dwelling. I usually add an antenna to the device
(if it has a telescopic antenna, you can clip additional wire to the top of the antenna with the
clamp portion of the clip being conduction and the handle being non-conductive), so you can
get more range and better reception.
AM is amplitude modulation and the signal is modulated by the height (amplitude) of the
radio wave. FM is frequency modulated (is wider band than AM) and uses line of sight
reception. FM is in a higher band than AM. FM is shorter range and more power. AM is
longer range and less power.
These concepts apply to the wireless internet as well. Key is a good open area to provide
an adequate reception envelope. Good Luck and God Bless.
Well, there's more loop area there to spray magnetic fields around than
there is in the cables in the wall. The nasty high-frequency currents
are probably coming from VFDs, switching supplies, and so on.
I build a lot of sensitive front end amps in instruments, so I feel your
pain. You still hear people advocating for star grounds, split ground
planes, and so on. Those were great in 1950, but in 2022 there's so
much RF and miscellaneous hash running round that a split ground plane
is as good as an antenna.(*)
(*) There are fairly popular antenna designs based on slots and patches
in planar conductors.
The point is, it's an issue, especially at certain parts of the AM dial, when a radio
is within 10 feet of the service mast outside my bathroom corner window. Outside
of the bathroom corner of the apt, the interference drops off exponentially.
On the ground floor is a light-industrial classification, prefabing shower doors and
such. No loud hums or buzzes every time material is cut or edges chamfered. Nothing
like that at all. Just a steadily increasing noise the closer one gets to that bathroom
window. The radio sits on top of a toilet about 8 feet from that corner of the bathroom
The mast itself is not the cause. It is a non conductor. It is
possible there is arcing between the wires inside the mast, but that
is not the mast causing the problem. If arcing is occurring, it's
due to frayed insulation on the wires. And I only mention it as a
possibility, not a diagnosis. Another possibility is corroded/loose
"bugs" ("utility splices" on your diagram). Again, not a diagnosis,
but a possibility. But either of those conditions - arcing within
the mast or bad connections at the top of the mast could make one
think that the mast is the cause of the problem. Take a portable
radio to the utility electric meter at the service entrance and see
what you hear with the radio held near the meter.
By itself, no. It ought to be a fairly passive pass-through for AC
current, with no mechanism for generating RFI. If there's a loose wire
or other bad connection, it could be making noise (and possibly overheating
and creating a safety hazard).
Seems to me there are two possible sources of the RFI you are suffering:
(1) Industrial equipment on that line (welders, big brush motors,
switching power supplies) which are generating RFI internally and
feeding it back into the mains. Here in the US, "Class A" equipment
(for use in business environments) is allowed a lot more RFI leakage
than "Class B" (residential), and industrial equipment is even worse.
(2) A physical fault in the mains wiring, which is causing arcing and
sparking, corona discharge, and so forth. Two fairly common problems
on power distribution poles are bad insulators (with electricity
arcing over them) and loose or defective ground connections. Arcing
in a circuit-breaker panel (e.g. a breaker going bad) could have
a similar effect.
In both cases the noise can travel quite a long distance along power
wiring to the point where it troubles you.
There are a few ways that can be used to track the location of a noise
source or fault of this type. Corona discharges and arcs often
generate a lot of ultrasonic noise, and there are ultrasound receivers
with directional microphones which shift this noise down into the
audible band. Arcing and corona can also generate noise up into the
VHF band which can be tracked using a receiver and a directional
antenna (e.g. a small hand-held Yagi). A spectrum analyzer hooked to
a directional antenna can be a useful tool as you may be able to see
specific noise lines bouncing up and down.
But close to that mast, in this apartment's bathroom, is where the interference
is strongest, out to perhaps a ten foot radius, which covers most of this
bathroom. Beyond that, the interference is, at worst, negligible.
And I understand that the head of the service mast - the part visible above and
to the left of the bathroom window, is only part of the package. I will take outside
a small portable radio, and walk around within 8 feet of the meters at the base of
the service mast, and see what happens at the frequency of the AM station I listen
Nice job deducing the likely point of entry. If your apartment
building has the usual array of smartmeters, see if the noise is also
coming from one particular smartmeter. You may need to REDUCE the
sensitivity of the AM radio by partially covering it with aluminum
Some questions and comments:
1. Is the noise present all the time or does it go on and off? If it
does one and off, try to correlate the timing with something in the
area the goes on and off at the same rate.
2. Does the noise appear (in the bathroom) at every frequency on your
radio? If you have an HF/SW radio, try different bands. If you have
a directional BCB antenna, such as a loop or ferrite rod antenna, you
might be able to find the source by direction finding.
3. If you have an oscilloscope, or a laptop with a sound card running
a software oscilloscope, try to get a screen print of the AM noise.
This will tell me something about what might be producing the noise.
Extra credit if you an SDR dongle and can produce a spectrum analyzer
output. If this is too much work (which it probably is), make an
audio recording of what you're hearing on the AM receiver and post the
MP3 file somewhere so we can analyze it. Try to make the recording
listening to a normally blank spot on the AM dial so that you're
hearing only the noise and not an AM station mixed with the noise.
4. Jumping ahead, if the noise is there 24x7 and never goes away,
then you're dealing with some kind of noisy device built into the
local infrastructure. Such a source is going to be difficult to find
and even more difficult to get the city to fix.
5. If the noise goes away at night, my guess(tm) is you're hearing
noise produced by a PV (photovoltaic) solar inverter. Most vendors
have EMI/RFI reduction kits available. If you have solar panels on
your roof or nearby, it might be a possible source. Something like
these. Make sure there's plenty of attenuation at BCB (broadcast
6. Check if your favored AM station is streaming on the internet or
does simulcast on an FM frequency. The interference might be less and
the filters more effective at 100MHz.
You should check the ground connection of the power conduit, where it
meets the service entrance.
Your boom box possibly has a screw connection marked 'antenna' for
a straight wire, or a telescoping antenna - both are usefull for FM
directional preferential reception. You may have to engage a switch
somewhere to select either.
You can forget about AM. In the region of any concentration of
commercial, residential or tranport activity, reception will be
noisy at best.
It's possible that the bathroom has a big mirror (which is a conductor, so shields/reflects RF) and that's part of why
reception is poor. Move the radio to different spots, and if you find a place that DOES have
reception, consider mounting a shelf there...
A fluorescent ballast can be a major noisemaker; have you tried switching things off in the vicinity?
Most AM noise I've found is worse between 700KHZ - 1MHZ. At my house, the AM is almost unlistenable, and I'm in the middle of a 5 acre lot. What I found by shutting off all breakers and turning them on one by one was several items contributing to the din. I found my outdoor motion sensing light fixtures were causing noise (took them apart and hard wired them then added Honeywell wall dusk to dawn switches), my alarm system (added low value capacitors across all keyboard lines at the panel), but the biggest offender was my wifi router. I took it apart and found the PFC cap bulged and changed it. It cut the noise down but it still generates a racket.