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UPS and radio interference

 
 
- Bobb -
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      09-10-2007
I have a few APC UPS's including one for stereo equipment and one for
computer. When I turn on PC, I hear whine when listening to AM signal of
tuner . I would think between the 2 UPS's I should get NO interference.
1. Am I maybe getting the whine " through the air" vs "thru the electrical
system" ?
2. How to tell ?
3. Wherever its source, how to stop it ?
Thanks

PS - whine not noticeable in lower AM range , but if on 1030AM ( and
higher frequencies) it's a steady high-pitched noise in addition to the
radio audio.



 
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Paul
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      09-10-2007
- Bobb - wrote:
> I have a few APC UPS's including one for stereo equipment and one for
> computer. When I turn on PC, I hear whine when listening to AM signal of
> tuner . I would think between the 2 UPS's I should get NO interference.
> 1. Am I maybe getting the whine " through the air" vs "thru the
> electrical system" ?
> 2. How to tell ?
> 3. Wherever its source, how to stop it ?
> Thanks
>
> PS - whine not noticeable in lower AM range , but if on 1030AM ( and
> higher frequencies) it's a steady high-pitched noise in addition to the
> radio audio.
>


Whether the UPS can cause a whine, will first depend on the architecture.
I have an SPS for example, the cheapest kind, and the inverter in one
of those does not operate, until the power fails. That one is not a
line interactive model.

There may be other kinds, that the inverter runs all the time, and that
could be what you are hearing.

I would say the most likely mechanism, is conducted emissions. Meaning
the noise is delivered on the cable, and not through the air.

And that is not all - if the noise is on the cable, the cable can function
as an antenna, and then the signal is also spilled into the air.

This is an example of a "filter brick". If placed on the input side
to the UPS, it would prevent noise from going back into your wall plug.
If place on the output side, it would prevent non-60Hz energy from
going to the load. Ideally, you want to buy these at some place that
doesn't charge a premium, as they can be expensive if you aren't
careful where you buy them. Newark sells them, but would not be the
cheapest place.

http://www.cor.com/PDF/N.pdf

Ouch - Digikey wants $92 for one!
http://www.digikey.com/scripts/DkSea...ame=CCM1649-ND

The single stage is cheaper, but still not what I want to see.
http://www.digikey.com/scripts/DkSea...ame=CCM1713-ND

Filters like that, are present on premium outlet strips. But perhaps
not dual stage filters, like the 10VN1 example. And since the 10VN1
is being sold as an electrical component, it still needs cords and
plugs fitted, and a housing around it to prevent electrocution
of the unsuspecting.

"filter banks" - but no attenuation specs.
http://www.tripplite.com/products/pr...productID=1347

My partial solution to this problem, it to put an antenna in a distant
part of the house, far away from the computer room. I do that for
OTA broadcast video. I have an antenna, a 300 ohm to 75 ohm balun,
a 20dB amplifier, maybe 75 feet of coax, and then a distribution
box in the computer room. By doing that, the TV antenna picks up
less interference from computers and related stuff. If I use an
antenna locally, I'll see herringbone patterns from my Antec power
supply

What I cannot tell you, is how best to "remote" A.M. pickup. There
are web pages that discuss building antennas, and maybe the
directional nature of one of these would help.

http://www.mindspring.com/~loop_antenna/

Paul

 
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- Bobb -
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      09-10-2007

"Paul" <(E-Mail Removed)> wrote in message news:fc4020$40c$(E-Mail Removed)...
>- Bobb - wrote:
>> I have a few APC UPS's including one for stereo equipment and one for
>> computer. When I turn on PC, I hear whine when listening to AM signal
>> of tuner . I would think between the 2 UPS's I should get NO
>> interference.
>> 1. Am I maybe getting the whine " through the air" vs "thru the
>> electrical system" ?
>> 2. How to tell ?
>> 3. Wherever its source, how to stop it ?
>> Thanks
>>
>> PS - whine not noticeable in lower AM range , but if on 1030AM ( and
>> higher frequencies) it's a steady high-pitched noise in addition to the
>> radio audio.
>>

>
> Whether the UPS can cause a whine, will first depend on the
> architecture.

<< Snipped to clarify this one point >>

I don't suspect the APC 350VA UPS to be the CAUSE. With no UPS's same
issue. It seems the PC is the CAUSE. With PC off (on its UPS in den) the
radio ( on a different APC 350VA UPS in LR) AND the radio ( on a third APC
350VA UPS in Bedroom) is fine.

Whatever the reason for the whine, I thought the UPS's would
isolate/filter it. Same thing still.
BTW I DO have a TV card/coax attached to the PC. Maybe THAT is the reason
( as you say - acting as antenna) ?

 
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Paul
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      09-11-2007
- Bobb - wrote:
>
> "Paul" <(E-Mail Removed)> wrote in message news:fc4020$40c$(E-Mail Removed)...
>> - Bobb - wrote:
>>> I have a few APC UPS's including one for stereo equipment and one for
>>> computer. When I turn on PC, I hear whine when listening to AM signal
>>> of tuner . I would think between the 2 UPS's I should get NO
>>> interference.
>>> 1. Am I maybe getting the whine " through the air" vs "thru the
>>> electrical system" ?
>>> 2. How to tell ?
>>> 3. Wherever its source, how to stop it ?
>>> Thanks
>>>
>>> PS - whine not noticeable in lower AM range , but if on 1030AM ( and
>>> higher frequencies) it's a steady high-pitched noise in addition to
>>> the radio audio.
>>>

>>
>> Whether the UPS can cause a whine, will first depend on the architecture.

> << Snipped to clarify this one point >>
>
> I don't suspect the APC 350VA UPS to be the CAUSE. With no UPS's same
> issue. It seems the PC is the CAUSE. With PC off (on its UPS in den) the
> radio ( on a different APC 350VA UPS in LR) AND the radio ( on a third
> APC 350VA UPS in Bedroom) is fine.
>
> Whatever the reason for the whine, I thought the UPS's would
> isolate/filter it. Same thing still.
> BTW I DO have a TV card/coax attached to the PC. Maybe THAT is the
> reason ( as you say - acting as antenna) ?
>


I don't see a reason to suspect the TV card. But if you wish, you can try
disconnecting the coax to the TV card, then see if your AM radio is
affected or not.

I believe you, when you say the problem disappears when the PC is powered
off. Since I've seen my Antec power supply, put a herringbone pattern on
my TV screen, I know that an ATX power supply can do it. I'm just surprised
that FCC rules don't apply to them. If I had to fix it, I'd want to try
something like the 10VN1. To me, it looks like a conducted emissions problem,
with switching noise flowing backwards on the PC's power cable. Placing a
filter as close as possible to the PC (i.e. use as short an AC cable between
the filter device and the computer), will reduce the loop size of the antenna.
Which is why, the filter should be inside the PSU...

The UPS could have a filter in it, but I doubt they provide a spec for its
effectiveness. The filter could be present, to help the UPS itself meet
FCC.

Paul
 
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w_tom
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      09-11-2007
On Sep 10, 4:43 pm, "- Bobb -" <b...@noemail.123> wrote:
> I don't suspect the APC 350VA UPS to be the CAUSE. With no UPS's same
> issue. It seems the PC is the CAUSE. With PC off (on its UPS in den) the
> radio ( on a different APC 350VA UPS in LR) AND the radio ( on a third APC
> 350VA UPS in Bedroom) is fine.
>
> Whatever the reason for the whine, I thought the UPS's would
> isolate/filter it. Same thing still.


Noise on an AM (medium wave) radio suggests bad computer hardware.
Often due to power supplies that are missing essential functions. But
other defective components (common in clone system built on price by
someone without electrical knowledge) inside the computer can also
cause that noise.

Remember, component manufactures need do no effort to restrict that
noise. Noise reduction is the responsibility of the computer
assembler. The guy who so often does not know how electricity works
even if A+ Certified.

You are fooling yourself if you think a typical UPS provides any
filtering or isolation. Does it claim that function in numbers? So
many computer assemblers who don't even know how electricity works
will promote myths about UPS functions.

View it yourself. Review those APC numeric specs. Numerous claims
can be made in color glossy sales brochures. Only place those claims
matter are in numeric specs. Where do those specs make claims to
provide filtering and isolation? They do not.

Meanwhile, what is the dirtiest electricity delivered to that
stereo, et al? When a UPS is in battery backup mode, then electricity
will often be the dirtiest. AC mains never provide electricity that
dirty. Electricity so dirty that it may even harm some small electric
motors. But again, did you learn about UPSes from popular myths - or
learn using science. Science starts with numeric specifications.

Remember, a UPS typically dumped into the market as cheap as
possible. Even a car battery that remains outside in adverse weather
will last twice as long as the rarely used battery inside a UPS.
Don't make assumptions for what that UPS does. It does one thing -
provide electricity during blackouts and extreme brownouts - nothing
more.

 
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