[RFI] Re: Interference Database - Ether RFI

[Martin Ewing <martin@aa6e.net>]

Jim,

Did I miss something on the list?  What database is this?  I am also 
interested in Ethernet RFI, and I have a small article on it at 
http://www.aa6e.net/aa6e/rfi/index.html.  If you look closely, there are 
birdies at least every 32 kHz on 100baseT, detectable all the way up 
into GHz territory.  Some are much worse that others, e.g., multiples of 
25 MHz.

I agree that ferrites help a lot, maybe 6-8 turns on a type 43 toroid 
core.  Resonance of Ether runs at HF wavelengths can lead to problems 
that can kill your Ethernet ports.  (I've done it with 100 Watts on 80 
M.)  I  try to use shielded twisted pair (STP) instead of UTP.  More 
than that, I'm mostly switching to WiFi networking around the house. 

Cheers,

Martin, AA6E

> Subject:
> [RFI] Intereference Database
> From:
> "Jim Brown" <jim@audiosystemsgroup.com>
> Date:
> Fri, 30 Jul 2004 11:35:15 -0500
>
> To:
> "RFI List" <rfi@contesting.com>, "dk1max@darc.de" <dk1max@darc.de>
>
>
> I think this database could be a lot more useful if it listed specific "birdie" or 
> carrier frequencies and cross referenced to specific equipment or 
> equipment types that produce those frequencies. 
>
> For example, I've tracked down specific frequencies in several HF CW 
> bands that are produced by the 10BaseT Ethernet gear in my office. They 
> are:
>
> 3511, 10106, 14029, 14030, 21052, and 28014.  I'm sure there are other 
> frequencies associated with 10BaseT, but I'm a CW guy and this is what I've 
> found.  :)  
>
> I've also learned that much of this is radiated by the CAT5 cable as a 
> common mode signal, and that it can be significantly attenuated by winding 
> the CAT5 cable around a ferrite core to form a choke. 
>
> Jim Brown  K9YC
>
>
>
>  

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