Most Ethernet MAC + PHY's (transciever's) and drivers out there are mostly
equiped with auto-negotiation feature and so will detect the speeds of your
network and will most likely select the highest speed setting at that time
unless forced into the slower 10Mbps speeds.
Both the 10/100Base-T and 1000Base-T Ethernet PHY's has a fundamental
frequency of 125MHz. This frequency also has a sub 62.5MHz EMI.
The fundamental 125MHz is not really mostly the highest EMI causing BUT its
much higher harmonics above 125MHz.
What we have seen that causes much havoc in these 1000Base-T network cards
is the 500MHz harmonic and the 1GHz. The 500MHz especially is bad...
Now if the transformers and the chokes on these PHY's are not well
designed, EMI can really be very bad especially the cheaper motherboards and
routers out in the market.
The Dell's and the Intel MB's are mostly quiter than most cheaper brands.
Dell takes care of their EMI more than any other brands out in the market.
On the 10Base-T mode, when you run music files on your network, you can
also see a 200MHz and nearby frequencies peak really high when see on a
spectrum analyzer.
So there are so many tecniques that these transformer + CMC manufacturers
(the good ones) come up with that take care of these EMI....
I have seen much of this, too. I found that the older 10baseT (10 MHz)
makes
less interference. You can force your computer into 10 MHz mode usually, but
many Ethernet devices (like hubs, routers, print servers) automatically
choose 100 MHz if available. The 32 or 64 kHz spurs seem to come from the
framing rate (a submultiple of the clock). What you hear will probably vary
depending on how much data is being sent. There is more at
http://www.aa6e.net/aa6e/rfi/ether_details.html .
I wonder if anyone has looked at the new 1000baseT. Possibly the higher
clock will take most of the energy out of the HF bands.
On 10/1/05, rfi-request@contesting.com <rfi-request@contesting.com> wrote:
>
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>
> Today's Topics:
>
> 1. Re: Internet Cable interference (Martin, AA6E)
> 2. Re: Internet Cable interference (Leigh L Klotz, Jr.)
> 3. Air Cleaner Interference (Jay Bareman)
> 4. Re: Air Cleaner Interference (John Wagner)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 29 Sep 2005 15:31:57 -0400
> From: "Martin, AA6E" <martin.ewing@gmail.com>
> Subject: Re: [RFI] Internet Cable interference
> To: rfi@contesting.com
> Message-ID: <6a2b366e05092912311f8cd668@mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> I have seen much of this, too. I found that the older 10baseT (10 MHz)
> makes
> less interference. You can force your computer into 10 MHz mode usually,
> but
> many Ethernet devices (like hubs, routers, print servers) automatically
> choose 100 MHz if available. The 32 or 64 kHz spurs seem to come from the
> framing rate (a submultiple of the clock). What you hear will probably
> vary
> depending on how much data is being sent. There is more at
> http://www.aa6e.net/aa6e/rfi/ether_details.html .
>
> I wonder if anyone has looked at the new 1000baseT. Possibly the higher
> clock will take most of the energy out of the HF bands.
>
> I can add a note about receivers vs antennas. It is correct that the RFI
> enters the Rx through the antenna. However, if your antenna is not
> balanced
> and there is RF (common mode) on your coax, your coax in the shack is part
> of your antenna, and you may get a lot more computer RFI. This is the flip
> side of "RF in the shack". Using a unun (ferrite beads) on your coax
> (outside the shack) might help quite a bit.
>
> 73 Martin AA6E
>
> On 9/29/05, Jim Brown <jim@audiosystemsgroup.com> wrote:
> >
> > On Tue, 27 Sep 2005 14:06:52 -0400, catwhiskr@aol.com wrote:
> >
> > >I have an S3 signal every 61 khz away from 14031.
> >
> > I don't know about the +/- 61 kHz component, but the 14030 stuff
> > is Ethernet-related, and is emitted by MANY devices that use
> > Ethernet for their interconnection, including, but not limited to,
> > cable modems. Some other frequencies I've identified are 10106,
> > 10120, 21052, 28016, and on 6 meters between 50 and 50.125. There
> > are others -- I mostly work CW.
> >
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 29 Sep 2005 12:33:48 -0700
> From: "Leigh L Klotz, Jr." <Leigh@WA5ZNU.org>
> Subject: Re: [RFI] Internet Cable interference
> To: "Martin, AA6E" <martin.ewing@gmail.com>, rfi@contesting.com
> Message-ID: <1128022431.144A0F7@dk11.dngr.org>
> Content-Type: text/plain; charset="us-ascii"; format="flowed"
>
> I am setting up fiber in my house, especialy for
> the long runs. I got a ton of it surplus for $20.
> Leigh / WA5ZNU
>
>
> ------------------------------
>
> Message: 3
> Date: Thu, 29 Sep 2005 15:48:02 -0500
> From: "Jay Bareman" <Radio_Q@mchsi.com>
> Subject: [RFI] Air Cleaner Interference
> To: <rfi@contesting.com>
> Message-ID: <20050929204807.5CE3E31919C@dayton.akorn.net>
> Content-Type: text/plain; charset="US-ASCII"
>
> I just had an unusual interference problem that I want to share with the
> group.
>
> I just bought a Honeywell 'desktop' HEPA type air filter that also
> included
> an ionizer option. It's pretty small and was just what I needed for my
> computer/radio room.
>
> I had it running about a day and noticed the red light which meant the
> filter needed to be cleaned would blink once a second or so but would not
> stay on solid red. According to the manual, solid red would mean the
> filter
> needed to be cleaned.
>
> The first evening I had it in the room, I turned on the radio and heard
> this
> repetitive impulsive noise and noticing the sky was very cloudy, I just
> assumed this was precipitation static from the oncoming storm. I always
> disconnect my antenna outside and then turn off the radio during a storm.
> Sure enough about an hour later we had a lightning storm and I thought
> nothing more of it.
>
> I have heard precipitation static build up before a storm and since there
> was a storm later, I thought I had the problem identified. I do remember
> being a little puzzled as usually the precipitation noise will increase
> the
> rep rate until there is a particularly strong impulse and the process will
> start over getting faster and faster until a large discharge. This one was
> unusual in that it was more consistent.
>
> This morning I plugged the antenna back in and turned on the radio and
> here
> was the impulsive noise again! The noise blanker took care of it but it
> was
> clearly something local. Walking around the house/yard with my R-10 tuned
> to 19 MHz convinced me it was coming from my house. I have horizontal loop
> and also a vertical dipole in the attic and the vertical had a much
> stronger
> signal. I then walked around the rooms of my house with my R-10 and
> nowhere
> in particular made the noise louder. I was checking all of the gear in my
> room and then checked the new air filter. I was about to leave it as the
> noise level was the same as everywhere else when I happened to notice the
> red light would flash every time I heard the impulsive noise. Turning off
> the UV option on the filter made the noise go away!
>
> The UV option, or what ever it was they were using to 'purify' the air was
> the culprit. It was most interesting the noise was not stronger right by
> the unit nor did it show any apparent polarization.
>
> I took the unit back to the store this afternoon and went back to a larger
> HEPA filter which has no 'air purifier' built into it. It's working fine
>
> 73's for now
>
> Jim K5QQ
>
>
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Thu, 29 Sep 2005 17:03:27 -0400
> From: "John Wagner" <jwagner@dxengineering.com>
> Subject: Re: [RFI] Air Cleaner Interference
> To: "'Jay Bareman'" <Radio_Q@mchsi.com>, <rfi@contesting.com>
> Message-ID:
> <4239A4FA4FF82E44AD6D215C41024B5C02EDB47A@exchange.summit.network>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Jim wrote:
> I just had an unusual interference problem that I want to share with the
> group.
>
> I just bought a Honeywell 'desktop' HEPA type air filter that also
> included
> an ionizer option. It's pretty small and was just what I needed for my
> computer/radio room.
>
> I had it running about a day and noticed the red light which meant the
> filter needed to be cleaned would blink once a second or so but would not
> stay on solid red. According to the manual, solid red would mean the
> filter
> needed to be cleaned.
>
> The first evening I had it in the room, I turned on the radio and heard
> this
> repetitive impulsive noise and noticing the sky was very cloudy, I just
> assumed this was precipitation static from the oncoming storm. I always
> disconnect my antenna outside and then turn off the radio during a storm.
> Sure enough about an hour later we had a lightning storm and I thought
> nothing more of it.
>
> I have heard precipitation static build up before a storm and since there
> was a storm later, I thought I had the problem identified. I do remember
> being a little puzzled as usually the precipitation noise will increase
> the
> rep rate until there is a particularly strong impulse and the process will
> start over getting faster and faster until a large discharge. This one was
> unusual in that it was more consistent.
>
> This morning I plugged the antenna back in and turned on the radio and
> here
> was the impulsive noise again! The noise blanker took care of it but it
> was
> clearly something local. Walking around the house/yard with my R-10 tuned
> to 19 MHz convinced me it was coming from my house. I have horizontal loop
> and also a vertical dipole in the attic and the vertical had a much
> stronger
> signal. I then walked around the rooms of my house with my R-10 and
> nowhere
> in particular made the noise louder. I was checking all of the gear in my
> room and then checked the new air filter. I was about to leave it as the
> noise level was the same as everywhere else when I happened to notice the
> red light would flash every time I heard the impulsive noise. Turning off
> the UV option on the filter made the noise go away!
>
> The UV option, or what ever it was they were using to 'purify' the air was
> the culprit. It was most interesting the noise was not stronger right by
> the unit nor did it show any apparent polarization.
>
> I took the unit back to the store this afternoon and went back to a larger
> HEPA filter which has no 'air purifier' built into it. It's working fine
>
> 73's for now
>
> Jim K5QQ
>
> I would suspect they are using an ionizer that produces ozone by some kind
> of spark! Probably feeding down the ground system of the house power.
> Interesting.
>
> 73 John
>
>
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>
>
>
>
>
> ------------------------------
>
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>
>
> End of RFI Digest, Vol 33, Issue 19
> ***********************************
>
--
Regards,
Max
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