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Computer network noise
I am running a Linksys WRT54G ver 3 wireless router at the QTH.
With some 3rd party firmware, it makes a good little router.

Problem is that it generates RF like crazy. Linksys knows about this problem and their solution is to slow the network down to 10Base-T. It helps with some of the emissions. I am not going to throw a bunch of ferrite and other things at this router. It is in an all plastic box (no shielding) and would take too long to re-engineer properly.

The main emissions come from my longer (unshielded) cat5 cables. If I disconnect all wired connections most of the noise ceases. The wireless side of the router is clean.

My question is what are you running?
Does it produce RF that you notice on HF or VHF?
If it is clean: Do you have cat5 runs across the house?

I am thinking maybe a used (small) commercial router or similar might produce less RF since they are usually a little better build and have metal enclosures, but the manufacturer might be less concerned about RF generated in a commercial environment. I don't even care if it has wireless, I have a commercial wireless access point that I can put in service.

Thoughts and ideas appreciated!

-Matt KF7DVN
Howdy Matt,

I had the same problem with a (At the time) top of the line 8 port HP ProCurve 10/100 network switch that I had mounted to the wall at the far end of my shack bench. Solid metal construction, no fans or moving parts of any kind, TONS of nasty interference on the radios. I noticed the same thing you were - unplug the network cables and the noise goes away. Plug one in at a time and each one produced quite a bit of noise of varying tones, and the sound from them would change based on network traffic. I finally got tired of it and plugged an old (Again, all-metal) Netgear (Back when they were still made by Bay Networks) 10 Mbps hub in to replace the HP and the interference went away.

10 Mbps wasn't bad for Internet traffic, as my DSL is only 1.5 Mbps anyway. However, it was really problematic for my internal LAN traffic, so I picked up some shielded CAT5e from a coworker and replaced some of my longer unshielded runs in the shack with it. I haven't gotten around to putting the HP 10/100 switch back in yet, but I can probably do that tomorrow after work and do some more testing if that'd help you out.

My guess is that most of the issues you are seeing are radiated emissions on the unshielded CAT 5 / 5e. If you're interested, I was thinking of picking up a spool of shielded stuff if it makes a difference over the unshielded stuff. Might have to get some CAT6 and 6A to test those, too.
W0ULF 2011+
ex KF7RJU 2011-2011
ex KC7YNP 1997-2007
Rigs: Heathkit RX-1 Mohawk Receiver and HX-10 Marauder Transmitter, IC-7410 Base HF w/AH-4, IC-2720 Mobile Dual Band, IC-V8000 Go-Bag 2m, IC-2820 base 2m/70cm (That goes to Field Day or goes in the other truck when I'm driving it), Kenwood TH-75A and Icom IC-92AD HTs.
Thanks Vaughn,

This is a not a new problem, so you don't have to rush to get your other switch in.

Depending on which router I end up with I may be putting a 10/100 switch in also. I am concerned about the same problem with the switch. Maybe I am just expecting it too much from unshielded cable.

I will be very interested in your results!

-Matt KF7DVN


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