Our AM/FM radio has severe noise when tuned on the AM band. We have lived
with this, because we mostly listen to FM, but these seem more directional
than the AM stations, so keep fading in & out when at anchor.

Today, I did a test to find the source of the noise. I had suspected it was
the battery charger but this turned out to be wrong. What it is, is a small
computer fan that we use to ventilate the cupboard where the refrig
compressor is located. Turn fan off and noise is gone!

The fan is new and is a typical 3" computer fan except it has two speeds
controlled by temperature.

The refrig unit itself has two fans - a 4" and a 2" and these do not seem to
cause any noise.

I suppose I can change the fan, but is there another way to eliminate the
radio interference?

"OldSailor" wrote in news:dtwDg.103772$hp.40793
@read2.cgocable.net:

I suppose I can change the fan, but is there another way to eliminate
the
radio interference?





Probably not. It's an electronic pulse generator running a sort of
stepper motor and they are very noisy, RF wise, in the MF/HF spectrum
computers don't worry about. I'm amazed your battery charger isn't
trashing it. We cannot hear anything on HF at the dock unless I cut the
breaker to the Guest dual 10A charger in the engine compartment. It just
radiates broadband noise something awful into the Icom M-802 HF receiver,
rendering it useless.

We had another electronic motor controller problem on the old boat that
had an Adler-Barbour 12V cold plate in the ice box. Of course, it only
made this repetitive, intermittent bzzt...bzzt...bzzt.bzzt.bzzt repeating
over and over just strong enough so you couldn't squelch it out on VHF
channel 16! Because you didn't monitor the other channels, hour after
hour, Adler-Barbour made it only jam Channel 16...driving you just CRAZY,
hour after hour listening at the helm. Took me a while to find it as I
never suspected 12V refridgeration would do such a thing so high in freq
on
FM....bzzt...bzzt...bzzt.bzzt.bzzt..........bzzt.. .bzzt...bzzt.bzzt.bzzt

Of course, NMEA networks running today with the manufacturers grounding
one side of the balanced network all over the place, radiate like hell,
too into the HF. I just shut our system down if I want to talk to
anyone.

"Larry" wrote

Probably not. It's an electronic pulse generator running a sort of
stepper motor and they are very noisy, RF wise, in the MF/HF spectrum
computers don't worry about. I'm amazed your battery charger isn't
trashing it.

Interesting that this particular fan causes excessive interference while the
two other fans that are built into the Waeco/Adler Barbour refrig unit do
not cause interference. All three are computer type muffin fans.

"OldSailor" wrote in news:kyJDg.67388$Uy1.29125
@read1.cgocable.net:

All three are computer type muffin fans.


Brushless DC.....that's the word I was looking for. Uses pulsating DC from
a little electronic noise maker...

"Larry" wrote

Brushless DC.....that's the word I was looking for. Uses pulsating DC
from
a little electronic noise maker...

Many of the fans are advertised as brushless - I thought it would be a good
thing - longer life.

I have two spare fans - Will have to run them on the boat and see if they
too cause interference.

In article ,
"OldSailor" wrote:

Our AM/FM radio has severe noise when tuned on the AM band. We have lived
with this, because we mostly listen to FM, but these seem more directional
than the AM stations, so keep fading in & out when at anchor.

Today, I did a test to find the source of the noise. I had suspected it was
the battery charger but this turned out to be wrong. What it is, is a small
computer fan that we use to ventilate the cupboard where the refrig
compressor is located. Turn fan off and noise is gone!

The fan is new and is a typical 3" computer fan except it has two speeds
controlled by temperature.

The refrig unit itself has two fans - a 4" and a 2" and these do not seem to
cause any noise.

I suppose I can change the fan, but is there another way to eliminate the
radio interference?




Well, now, if you really want to eliminate the noise you can do one of
three things.

1. Buy a different fan that doesn't make noise in the MF Radio Spectrum.
They do make them.....
2. See if you can supress the noise coming out of the current fan, with
the appropriarte Ferrite Beads, and ByPass Capacitors, or get one
of the fancy NUMAR or Ormicon Noise Filters for the DC wires
feeding the fan. (wires most likely are acting like an antenna)
3. Get ride of the fan altogether.....or maybe just turn it off while
your listening to the radio.

Bruce in alaska one with years of experience, in noise supression, on
Maritime Mobile Stations.....
--
add a 2 before @

"Bruce in Alaska" wrote

1. Buy a different fan that doesn't make noise in the MF Radio Spectrum.
They do make them.....

I have two different fans - I will test them. The refrigerator fans don't
cause noise, but they are powered from refrigeration Danfoss module, while
noisy fan is powered direct from panel.

2. See if you can supress the noise coming out of the current fan, with
the appropriarte Ferrite Beads, and ByPass Capacitors, or get one
of the fancy NUMAR or Ormicon Noise Filters for the DC wires
feeding the fan. (wires most likely are acting like an antenna)

I will look at Radio Shack/The Source and see what they offer. Would it
help to use a shielded power cable?


3. Get ride of the fan altogether.....or maybe just turn it off while
your listening to the radio.

The fan is required to keep the refrig compressor compartment at acceptable
temperature - Maybe if I moved to Alaska I could turn it off , otherwise
our choice is cold beer or music.

As another option, I could relocate the AM/FM antenna - it is quite close to
the DC power panel. Could use one of those VHF/AMFM splitters and eliminate
AM/FM antenna altogether - would that help?

OldSailor wrote:
"Bruce in Alaska" wrote
1. Buy a different fan that doesn't make noise in the MF Radio Spectrum.
They do make them.....

I have two different fans - I will test them. The refrigerator fans don't
cause noise, but they are powered from refrigeration Danfoss module, while
noisy fan is powered direct from panel.

2. See if you can supress the noise coming out of the current fan, with
the appropriarte Ferrite Beads, and ByPass Capacitors, or get one
of the fancy NUMAR or Ormicon Noise Filters for the DC wires
feeding the fan. (wires most likely are acting like an antenna)

I will look at Radio Shack/The Source and see what they offer. Would it
help to use a shielded power cable?


3. Get ride of the fan altogether.....or maybe just turn it off while
your listening to the radio.

The fan is required to keep the refrig compressor compartment at acceptable
temperature - Maybe if I moved to Alaska I could turn it off , otherwise
our choice is cold beer or music.

As another option, I could relocate the AM/FM antenna - it is quite close to
the DC power panel. Could use one of those VHF/AMFM splitters and eliminate
AM/FM antenna altogether - would that help?





Along the lines Bruce suggested, it
might be worthwhile identifying the
transmission mechanism of the noise. It
may be radiated and picked up by the
radio antenna, or it may be carried over
the 12 VDC power wires.

The simplest test is to short the
antenna terminals at the radio if you
can. To see if the noise is being
carried by the 12 VDC wires, try using a
portable radio (with its own batteries)
in the same spot.

Usually, it is much easier to clean up
the 12 VDC power system (at least at the
radio connection).

Good luck.

Chuck

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"chuck" wrote

Along the lines Bruce suggested, it
might be worthwhile identifying the
transmission mechanism of the noise. It
may be radiated and picked up by the
radio antenna, or it may be carried over
the 12 VDC power wires.

The simplest test is to short the
antenna terminals at the radio if you
can. To see if the noise is being
carried by the 12 VDC wires, try using a
portable radio (with its own batteries)
in the same spot.

The portable radio test should be easy - I THINK we have one somewhere! The
AM/FM antenna is just an automotive type installed horizontally in a
locker - Is it OK to short the connection plug (RCA type). The noise is
acros the whole AM band but does not occur on FM - would this indicate it is
more likely radiated noise?

Usually, it is much easier to clean up
the 12 VDC power system (at least at the
radio connection).


Thanks for the input

OldSailor wrote:

The portable radio test should be easy - I THINK we have one somewhere! The
AM/FM antenna is just an automotive type installed horizontally in a
locker - Is it OK to short the connection plug (RCA type). The noise is
acros the whole AM band but does not occur on FM - would this indicate it is
more likely radiated noise?
\

Not necessarily. You didn't think it
would be THAT easy, did you? ;-)

Chuck

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