[RFI] Ethernet RFI

Ford Peterson ford at cmgate.com
Sun Jan 23 01:33:00 EST 2005

> On Sat, 22 Jan 2005 21:28:10 -0600, Ford Peterson wrote:
>>I'm willing to bet my next paycheck that the noise will be gone 
>>if they are properly shielded by retaining the 'pairs' in the
>>proper sequence. 
> You'd better go for a paycheck loan, Ford. :) You (and the tutorial) 
> are absolutely correct that a twisted pair helps TREMENDOUSLY in 
> killing DIFFERENTIAL mode coupling to/from the cable. And we have a 
> lot of experience with loudspeaker cables that says that twisted 
> pair is FAR superior to parallel wire (zip cord) in minimizing RFI. 
> But twisting helps NOT AT ALL when the cable is excited COMMON MODE 
> and radiates as a long wire antenna. That's what the chokes can 
> reduce (a LOT). 
> My experience with HF trash from Ethernet cable is that it is all 
> COMMON MODE radiation from the cable, added (sometimes) to direct 
> radiation from the box itself. 
> Jim Brown  K9YC


My bet was a safe one.  I haven't had a paycheck since 1988.  I seriously doubt I will have one any time soon.  But if I do, I'll look you up on QRZ and settle up...

Many stations use Ethernet to connect stations in a multi-op, and even connect it directly to their radios without interference.  It is possible that the router itself is at fault.  My experience has been that the power supplies supporting the routers are more troublesome than the data exchange.  My comment was speculative, but practical.  If the connectors are correct, then look elsewhere.  

Have a great day...  And good luck with isolating your noise problems.

ford at cmgate.com

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