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OT Local QRN what is it?

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Bill Hammond

OT Local QRN what is it?

I have been chasing this noise in my urban neighborhood for several years now. It usually visits during the daylight hours and stays for several hours. It has a rhythm and is across all frequencies and bands. I have pulled the big switch in my house and the noise is still with me (listening on battery powered rigs). Neighbors on all sides of my city sized lot have swimming pools and my first suspicion is noise generated by circulation pumps.

Here are two recordings (on a K3 of coarse). Why not ask the most discriminating radio fans in the world their opinions on the source?

http://www.flickr.com/photos/ak5x/4279625626/in/photostream/

http://www.flickr.com/photos/ak5x/4279577818/in/photostream/

Bill Hammond-AK5X
[hidden email]
[hidden email]
[hidden email]
K3 #69
K2/100 #4637
K1 #2033
KX1 #1023
T1

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John, KD8K

Re: OT Local QRN what is it?

Here is a web site that might be of help to you in identifying this. It
is the RF noise identification web site.

http://www.arrl.org/tis/info/HTML/rfi-noise/appliances.html

To me it sounds a lot like the "treadmill" noise clip.

Hope this is of help.

73, John KD8K

Bill Hammond wrote:

> I have been chasing this noise in my urban neighborhood for several years now. It usually visits during the daylight hours and stays for several hours. It has a rhythm and is across all frequencies and bands. I have pulled the big switch in my house and the noise is still with me (listening on battery powered rigs). Neighbors on all sides of my city sized lot have swimming pools and my first suspicion is noise generated by circulation pumps.
>
> Here are two recordings (on a K3 of coarse). Why not ask the most discriminating radio fans in the world their opinions on the source?
>
> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>
>
> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>
>
> Bill Hammond-AK5X
> [hidden email]
> [hidden email]
> [hidden email]
> K3 #69
> K2/100 #4637
> K1 #2033
> KX1 #1023
> T1
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>

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k1tl

Re: OT Local QRN what is it?

In reply to this post by Bill Hammond

Bill,
Sounds like a treadmill as my next door neighbor has one and cause problems,
mostly on the 30m band. He also has a Kenmore HE-3 washing machine which is
an RFI generator. My 30m 4sq is about 200 feet from his house and cause an
S9 hash noise on 10.103, 10.118, etc...PITA ! ! !

73 es gl

Tom/k1tl...
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Will - AI4VE

Re: OT Local QRN what is it?

In reply to this post by Bill Hammond

Bill,

I'm afraid it's not unique to your neighborhood. I've heard the same noise at my station in NC. It doesn't match the treadmill example referred to (at least at my QTH) because the roughly 3 KHz 'beat frequency' doesn't vary. When it's there it is audible from about the 17m ham band continuously down through the 160m band. Like you I also hear it during the day but mostly on weekends since I work during the week. I'd love to know what it is because when it's present I may as well quit operating.

Will Ravenel, AI4VE
[hidden email]

On Jan 16, 2010, at 2:34 PM, Bill Hammond wrote:

Bill Hammond

Re: OT Local QRN what is it? UPDATE!

In reply to this post by Bill Hammond

Thank you Elecraft reflector members for all of the great suggestions on this QRN problem.. With your help I was able to locate the problem. I would of not found it without your help.

Now, I have no idea what to do about the issue, perhaps nothing. I now know the source.

It's my neighbors treadmill. We share a power transformer (underground utilities). Although I bet the noise is from a motor arching and most likely is radiating at the motor as opposed to being carried on the power line. I have hope as he is not a ultra marathon runner and his runs rarely cause a QRT of over an hour.

If you want to hear the sound click on the Flickr link:
http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
http://www.flickr.com/photos/ak5x/4279577818/in/photostream/

Thank you again list members for allowing me to tap the collective :)
73,
Bill
AK5X

On Jan 16, 2010, at 1:34 PM, Bill Hammond wrote:

Bill Hammond-AK5X
[hidden email]
[hidden email]
[hidden email]
K3 #69
K2/100 #4637
K1 #2033
KX1 #1023
T1

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Phil Hystad

Re: OT Local QRN what is it? UPDATE!

We have a treadmill and it DEFINITELY radiates noise. It produces a 20/9 signal on my Icom 706 truck when I am sitting in the driveway and my wife is on the treadmill. As I drive away, I can still hear the noise as it decreases in strength until about 1 mile away where it disappears into the background noise.

Our treadmill is NordicTrack APEX 6100. Noisy little beasts. If I remember, they are about 20/9 peaks separated every roughly 20 KHz across all bands. They are strongest in the 10 to 20 MHz range though.

You though have one advantage over your neighbor. You are licensed to transmit RF and he isn't (I presume that he isn't licensed).

73, phil, K7PEH

On Jan 19, 2010, at 10:12 AM, Bill Hammond wrote:

> Thank you Elecraft reflector members for all of the great suggestions on this QRN problem.. With your help I was able to locate the problem. I would of not found it without your help.
>
> Now, I have no idea what to do about the issue, perhaps nothing. I now know the source.
>
> It's my neighbors treadmill. We share a power transformer (underground utilities). Although I bet the noise is from a motor arching and most likely is radiating at the motor as opposed to being carried on the power line. I have hope as he is not a ultra marathon runner and his runs rarely cause a QRT of over an hour.
>
> If you want to hear the sound click on the Flickr link:
> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>
> Thank you again list members for allowing me to tap the collective :)
> 73,
> Bill
> AK5X
>
>
> On Jan 16, 2010, at 1:34 PM, Bill Hammond wrote:
>
>> I have been chasing this noise in my urban neighborhood for several years now. It usually visits during the daylight hours and stays for several hours. It has a rhythm and is across all frequencies and bands. I have pulled the big switch in my house and the noise is still with me (listening on battery powered rigs). Neighbors on all sides of my city sized lot have swimming pools and my first suspicion is noise generated by circulation pumps.
>>
>> Here are two recordings (on a K3 of coarse). Why not ask the most discriminating radio fans in the world their opinions on the source?
>>
>> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>>
>>
>> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>>
>>
>> Bill Hammond-AK5X
>> [hidden email]
>> [hidden email]
>> [hidden email]
>> K3 #69
>> K2/100 #4637
>> K1 #2033
>> KX1 #1023
>> T1
>>
>>
>>
>>
>
> Bill Hammond-AK5X
> [hidden email]
> [hidden email]
> [hidden email]
> K3 #69
> K2/100 #4637
> K1 #2033
> KX1 #1023
> T1
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Ken Kopp-3

Re: OT Local QRN what is it? UPDATE!

The SCR motor controllers, as well as the "tread"
belts ... think Van de Graaff generator ... are significant
noise sources,

73! Ken Kopp - K0PP
[hidden email]
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David Christ

Re: OT Local QRN what is it? UPDATE!

In reply to this post by Phil Hystad

Good treadmiils use a DC motor in the 2 HP Range. If they govern
the speed by driving the motor with a variable width pulse it might
explain why they are so RF noisy. Given all the unshielded wiring
between the controller board, the motor, and the display console it
is no small wonder they radiate RF. Trying to tame the beast could
be tough.

David K0LUM

At 10:51 AM -0800 1/19/10, Phil Hystad wrote:

>We have a treadmill and it DEFINITELY radiates noise. It produces a
>20/9 signal on my Icom 706 truck when I am sitting in the driveway
>and my wife is on the treadmill. As I drive away, I can still hear
>the noise as it decreases in strength until about 1 mile away where
>it disappears into the background noise.
>
>Our treadmill is NordicTrack APEX 6100. Noisy little beasts. If I
>remember, they are about 20/9 peaks separated every roughly 20 KHz
>across all bands. They are strongest in the 10 to 20 MHz range
>though.
>
>You though have one advantage over your neighbor. You are licensed
>to transmit RF and he isn't (I presume that he isn't licensed).
>
>73, phil, K7PEH
>
>
>On Jan 19, 2010, at 10:12 AM, Bill Hammond wrote:
>
> > Thank you Elecraft reflector members for all of the great
>suggestions on this QRN problem.. With your help I was able to
>locate the problem. I would of not found it without your help.
>>
>> Now, I have no idea what to do about the issue, perhaps nothing.
>>I now know the source.
>>
> > It's my neighbors treadmill. We share a power transformer
>(underground utilities). Although I bet the noise is from a motor
>arching and most likely is radiating at the motor as opposed to
>being carried on the power line. I have hope as he is not a ultra
>marathon runner and his runs rarely cause a QRT of over an hour.
>
> > 73,
>> Bill
> > AK5X

Don Ehrlich

Re: [Elecraft] OT Local QRN what is it? UPDATE!

In reply to this post by Bill Hammond

Bill,

My own treadmill causes severe interference here in the house. I'm the only
one who uses it so it does not affect my own radio but it blanks out any AM
radio in the house that happens to be turned on. I reduced the noise to an
insignificant level by simply plugging a few microfarads of film capacitor
into the same power outlet that the treadmill is plugged in to. I just
wired up the capacitors to an AC plug in a neat little package that looks
like a big wall wart. The interference definitely is carried throughout the
house by the wiring. I suspect that if your neighbor would agree to plug a
similar module into the same outlet as is his treadmill that it would
improve your noise situation.

Don K7FJ

> Thank you Elecraft reflector members for all of the great suggestions on
> this QRN problem.. With your help I was able to locate the problem. I
> would of not found it without your help.
>
> Now, I have no idea what to do about the issue, perhaps nothing. I now
> know the source.
>
> It's my neighbors treadmill. We share a power transformer (underground
> utilities). Although I bet the noise is from a motor arching and most
> likely is radiating at the motor as opposed to being carried on the power
> line. I have hope as he is not a ultra marathon runner and his runs
> rarely cause a QRT of over an hour.
>
> If you want to hear the sound click on the Flickr link:
> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>
> Thank you again list members for allowing me to tap the collective :)
> 73,
> Bill
> AK5X
>
>
> On Jan 16, 2010, at 1:34 PM, Bill Hammond wrote:
>
>> I have been chasing this noise in my urban neighborhood for several years
>> now. It usually visits during the daylight hours and stays for several
>> hours. It has a rhythm and is across all frequencies and bands. I have
>> pulled the big switch in my house and the noise is still with me
>> (listening on battery powered rigs). Neighbors on all sides of my city
>> sized lot have swimming pools and my first suspicion is noise generated
>> by circulation pumps.
>>
>> Here are two recordings (on a K3 of coarse). Why not ask the most
>> discriminating radio fans in the world their opinions on the source?
>>
>> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>>
>>
>> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>>
>>
>> Bill Hammond-AK5X
>> [hidden email]
>> [hidden email]
>> [hidden email]
>> K3 #69
>> K2/100 #4637
>> K1 #2033
>> KX1 #1023
>> T1
>>
>>
>>
>>
>
> Bill Hammond-AK5X
> [hidden email]
> [hidden email]
> [hidden email]
> K3 #69
> K2/100 #4637
> K1 #2033
> KX1 #1023
> T1
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Steven Pituch-3

Re: [Elecraft] OT Local QRN what is it? UPDATE!

Hi All,
I had mentioned previously that I just ordered a nice treadmill after a lot
of research. When I read about this possible interference I sent an email
to the company. Within an hour I got a phone call from a very knowledgeable
person. He stated that as far as he knows all treadmills except Precor and
Woodway use PWM to regulate the DC motor. He said RFI could emanate from
the motor along the AC plug, or radiate from the PWM circuit. He said that
if it was from the PWM it would be very difficult to resolve, as it would be
picked up by the antenna. He said both types of interference were
definitely possible. He also stated that if I wanted to buy a Precor or
Woodway I would be talking about $4500 for an entry level machine.

I talked it over with my wife and since I doubt I will be on my K3 while on
the treadmill we decided to keep the treadmill we ordered. I feel sorry for
any ham who is suffering RFI from a neighbor's treadmill. Better to work
with them than to call the FCC on them.

Steve, W2MY

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David Christ

Re: [Elecraft] OT Local QRN what is it? UPDATE!

Very interesting. I own a Precor treadmill. I just went down and
tested it. No interference at all on 20. Didn't check anything else.

Didn't pay $4500 for it either. Got it from a dealer friend of mine.
It was a new one that never worked so it sat in the warehouse. He
said I could have it if I could fix it. In 10 minutes I found a bad
RJ-45 connector. Works great now.

Maybe I should put a small shelf on it so I can work treadmill mobile.

Any lawyers out there? In a situation like this where a device's
design and construction creates interference, does the owner have all
the abatement responsibility or does the manufacturer retain the
responsibility as they manufactured a defective device incapable of
being operated legally?

David K0LUM

At 10:20 AM -0600 1/20/10, Steven Pituch wrote:
><snip>

> He stated that as far as he knows all treadmills except Precor and
>Woodway use PWM to regulate the DC motor. He said RFI could emanate from
>the motor along the AC plug, or radiate from the PWM circuit. He said that
>if it was from the PWM it would be very difficult to resolve, as it would be
>picked up by the antenna. He said both types of interference were
>definitely possible. He also stated that if I wanted to buy a Precor or
>Woodway I would be talking about $4500 for an entry level machine.
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Bob-270

Re: [Elecraft] OT Local QRN what is it? UPDATE!

In reply to this post by Don Ehrlich

If it were me I do not think I would furnish or propose any home made
device as a solution.
Were there to be a failure in the treadmill shorty thereafter you can be
sure where the blame
would be placed. A really worse case scenario would be a fire. Then
it would be a let the law
suits begin situation.

I would look around for some type of commercial line filter that could
be placed in the line.
To keep the money in the Ham marketplace here is a possible if the
treadmill is under a 7 amp
load:

http://www.arraysolutions.com/Products/nqnaclinefilter.htm

I have no experience with this unit, or financial interest in it
either. But if the interference was
real aggravating to me I'd invest in a potential solution and propose
something along these lines
as a "loaner".

73,
Bob
K2TK

Don Ehrlich wrote:

> Bill,
>
> My own treadmill causes severe interference here in the house. I'm the only
> one who uses it so it does not affect my own radio but it blanks out any AM
> radio in the house that happens to be turned on. I reduced the noise to an
> insignificant level by simply plugging a few microfarads of film capacitor
> into the same power outlet that the treadmill is plugged in to. I just
> wired up the capacitors to an AC plug in a neat little package that looks
> like a big wall wart. The interference definitely is carried throughout the
> house by the wiring. I suspect that if your neighbor would agree to plug a
> similar module into the same outlet as is his treadmill that it would
> improve your noise situation.
>
> Don K7FJ
>
>
>
>
>> Thank you Elecraft reflector members for all of the great suggestions on
>> this QRN problem.. With your help I was able to locate the problem. I
>> would of not found it without your help.
>>
>> Now, I have no idea what to do about the issue, perhaps nothing. I now
>> know the source.
>>
>> It's my neighbors treadmill. We share a power transformer (underground
>> utilities). Although I bet the noise is from a motor arching and most
>> likely is radiating at the motor as opposed to being carried on the power
>> line. I have hope as he is not a ultra marathon runner and his runs
>> rarely cause a QRT of over an hour.
>>
>> If you want to hear the sound click on the Flickr link:
>> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>>
>> Thank you again list members for allowing me to tap the collective :)
>> 73,
>> Bill
>> AK5X
>>
>>
>> On Jan 16, 2010, at 1:34 PM, Bill Hammond wrote:
>>
>>
>>> I have been chasing this noise in my urban neighborhood for several years
>>> now. It usually visits during the daylight hours and stays for several
>>> hours. It has a rhythm and is across all frequencies and bands. I have
>>> pulled the big switch in my house and the noise is still with me
>>> (listening on battery powered rigs). Neighbors on all sides of my city
>>> sized lot have swimming pools and my first suspicion is noise generated
>>> by circulation pumps.
>>>
>>> Here are two recordings (on a K3 of coarse). Why not ask the most
>>> discriminating radio fans in the world their opinions on the source?
>>>
>>> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>>>
>>>
>>> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>>>
>>>
>>> Bill Hammond-AK5X
>>> [hidden email]
>>> [hidden email]
>>> [hidden email]
>>> K3 #69
>>> K2/100 #4637
>>> K1 #2033
>>> KX1 #1023
>>> T1
>>>
>>>
>>>
>>>
>>>
>> Bill Hammond-AK5X
>> [hidden email]
>> [hidden email]
>> [hidden email]
>> K3 #69
>> K2/100 #4637
>> K1 #2033
>> KX1 #1023
>> T1
>>
>>
>>

Steven Pituch-3

Re: [Elecraft] OT Local QRN what is it? UPDATE!

In reply to this post by David Christ

Hi David,
I don't know if treadmills are FCC Part 15 devices. I have not found the FCC
statement in the manual for the treadmill I ordered. Part 15 devices are
allowed to radiate as long as someone doesn't complain of the RFI to a
licensed service. If that happens try to convince your neighbor that it is
illegal to operate his plasma TV.

Steve, W2MY
(I'm not a lawyer)

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Don Wilhelm-4

Re: [Elecraft] OT Local QRN what is it? UPDATE!

In reply to this post by Bob-270

Bob,

You are so right about that. I might further state that anything which
plugs into the AC outlet must have UL or other testing lab approval
stickers on it, so giving a neighbor an unapproved homebrew device opens
to door for liability.

73,
Don W3FPR

Bob wrote:

> If it were me I do not think I would furnish or propose any home made
> device as a solution.
> Were there to be a failure in the treadmill shorty thereafter you can be
> sure where the blame
> would be placed. A really worse case scenario would be a fire. Then
> it would be a let the law
> suits begin situation.
>
> I would look around for some type of commercial line filter that could
> be placed in the line.
> To keep the money in the Ham marketplace here is a possible if the
> treadmill is under a 7 amp
> load:
>
> http://www.arraysolutions.com/Products/nqnaclinefilter.htm
>
> I have no experience with this unit, or financial interest in it
> either. But if the interference was
> real aggravating to me I'd invest in a potential solution and propose
> something along these lines
> as a "loaner".
>
> 73,
> Bob
> K2TK
>
>
> Don Ehrlich wrote:
>
>> Bill,
>>
>> My own treadmill causes severe interference here in the house. I'm the only
>> one who uses it so it does not affect my own radio but it blanks out any AM
>> radio in the house that happens to be turned on. I reduced the noise to an
>> insignificant level by simply plugging a few microfarads of film capacitor
>> into the same power outlet that the treadmill is plugged in to. I just
>> wired up the capacitors to an AC plug in a neat little package that looks
>> like a big wall wart. The interference definitely is carried throughout the
>> house by the wiring. I suspect that if your neighbor would agree to plug a
>> similar module into the same outlet as is his treadmill that it would
>> improve your noise situation.
>>
>> Don K7FJ
>>
>>
>>
>>
>>
>>> Thank you Elecraft reflector members for all of the great suggestions on
>>> this QRN problem.. With your help I was able to locate the problem. I
>>> would of not found it without your help.
>>>
>>> Now, I have no idea what to do about the issue, perhaps nothing. I now
>>> know the source.
>>>
>>> It's my neighbors treadmill. We share a power transformer (underground
>>> utilities). Although I bet the noise is from a motor arching and most
>>> likely is radiating at the motor as opposed to being carried on the power
>>> line. I have hope as he is not a ultra marathon runner and his runs
>>> rarely cause a QRT of over an hour.
>>>
>>> If you want to hear the sound click on the Flickr link:
>>> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>>> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>>>
>>> Thank you again list members for allowing me to tap the collective :)
>>> 73,
>>> Bill
>>> AK5X
>>>
>>>
>>> On Jan 16, 2010, at 1:34 PM, Bill Hammond wrote:
>>>
>>>
>>>
>>>> I have been chasing this noise in my urban neighborhood for several years
>>>> now. It usually visits during the daylight hours and stays for several
>>>> hours. It has a rhythm and is across all frequencies and bands. I have
>>>> pulled the big switch in my house and the noise is still with me
>>>> (listening on battery powered rigs). Neighbors on all sides of my city
>>>> sized lot have swimming pools and my first suspicion is noise generated
>>>> by circulation pumps.
>>>>
>>>> Here are two recordings (on a K3 of coarse). Why not ask the most
>>>> discriminating radio fans in the world their opinions on the source?
>>>>
>>>> http://www.flickr.com/photos/ak5x/4279625626/in/photostream/
>>>>
>>>>
>>>> http://www.flickr.com/photos/ak5x/4279577818/in/photostream/
>>>>
>>>>
>>>> Bill Hammond-AK5X
>>>> [hidden email]
>>>> [hidden email]
>>>> [hidden email]
>>>> K3 #69
>>>> K2/100 #4637
>>>> K1 #2033
>>>> KX1 #1023
>>>> T1
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>> Bill Hammond-AK5X
>>> [hidden email]
>>> [hidden email]
>>> [hidden email]
>>> K3 #69
>>> K2/100 #4637
>>> K1 #2033
>>> KX1 #1023
>>> T1
>>>
>>>
>>>
>>>
> ______________________________________________________________
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P.B. Christensen

Re: [Elecraft] OT Local QRN what is it? UPDATE!

In reply to this post by Bob-270

> I would look around for some type of commercial line filter that could
> be placed in the line.

Before purchasing a line RFI/EMI filter, the noise path and manner of
propagation requires investigation. If RFI radiation is occurring as a
result of coupling from a power supply or display module (for example) onto
a cable wiring harness but is not associated with the AC line path, then
adding a line filter is a wasted expense.

Techniques used for investigating and localizing a noise path can be found
in the RFI mail list archives.

Paul, W9AC

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Don Ehrlich

Re: [Elecraft] OT Local QRN what is it? UPDATE!

Well ... a 2 horse motor (output) will be consuming about 1.5 Kw if
operating at its maximum rating. Even if not maxed out it is likely to be
well over the ratings of any commercial line filter that we are likely to
find.

Localizing the source is no problem. It is the treadmill. If the common
mode and differential mode conducted noise in the line cord going to the
wall can be suppressed then the noise is contained to the treadmill. My
homebrew approach worked for me but the point about liability is well taken.
The only completely safe way to handle the noise may be to add a few pounds
of ferrite to the line cord to suppress the common mode HF current. Just
kidding .. same problem of liability .. or at least blame for whatever
problems the user may perceive. My guess is there is not really anything
to be done.

In years past I was an avionics EMI hunter and I just cannot resist the
temptation to comment. But I'm done now.

Don K7FJ

>> I would look around for some type of commercial line filter that could
>> be placed in the line.
>
> Before purchasing a line RFI/EMI filter, the noise path and manner of
> propagation requires investigation. If RFI radiation is occurring as a
> result of coupling from a power supply or display module (for example)
> onto
> a cable wiring harness but is not associated with the AC line path, then
> adding a line filter is a wasted expense.
>
> Techniques used for investigating and localizing a noise path can be found
> in the RFI mail list archives.
>
> Paul, W9AC
>
>
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