[TenTec] notch filter for Eagle?

Jim Brown k9yc at audiosystemsgroup.com
Thu Jul 20 13:28:35 EDT 2017

On 7/20/2017 7:38 AM, Joe Papworth via TenTec wrote:
> Those carriers around 14030 may be from a wireless router.

More precisely, they are leakage from wired Ethernet systems. Wired 
Ethernet uses a free-running clock that is synchronized with the 
Ethernet Hub or Switch; we typically hear our own system and those of 
close-in neighbors. When I lived in Chicago with houses spaced about 40 
ft, I typically heard 3-5 of them spaced from about 14029.5 to about 
14030.5. There are other clusters on 15 and 10M. It's easy to figure out 
which signal is coming from your system by killing power to the 

These signals are radiated by the Ethernet cable, and can be suppressed 
by winding the Ethernet cable through a ferrite core to form a common 
mode choke, following the guidelines for RG8X-size cable in 
k9yc.com/RFI-Ham.pdf Virtually all WiFi access points and cable/DSL 
modems include an Ethernet port, so their wiring also radiates this trash.

Note also that both the computers and the Ethernet Hub/Switch/Router are 
sources of this noise, so if the wired Ethernet cables are longer than 
about a tenth of a wavelength, a choke may be required on both ends. 
Even better, avoid Ethernet by using only WiFi, so the only noise source 
is that Router/Modem. The cable(s) interconnecting them will be shorter, 
hence poorer antennas, and they will be the only ones you need to choke.

73, Jim K9YC

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