[RFI] Internet Cable interference

Martin, AA6E martin.ewing at gmail.com
Thu Sep 29 15:31:57 EDT 2005

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 at audiosystemsgroup.com> wrote:
> On Tue, 27 Sep 2005 14:06:52 -0400, catwhiskr at 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.

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