[RFI] Cable Modem Interference

Peter D. Vouvounas wb3fsr@home.com
Wed, 28 Nov 2001 10:51:28 -0500

Now that so many hams have cable modem I'd like to ask for feedback
regarding experiences with noise generation into the HF bands.  Particularly
3.5 - 4 MHz.

It's now been three years give or take a week that my wife N2THE and I
WB3FSR, have been in our home by the Ocean in New Jersey -  Since the move
in date we've had cable modem on-line using the Motorola CyberSurfer modem
supplied by Comcast @ home....

While tracking a plethora of noise sources i.e. Power Company, Cable
Company, etc I've found a tremendous amount of noise on the 80/75 Meter
bands from the cable modem. The cable modem feeds a hub servicing other
computers in the home & home office.  I've found no interference from the
hub - If I remove the coax input to the cable modem the noise drops
appreciable - If I remove power from the cable modem the same major drop in
noise. Tried wrapping the modem in aluminum foil and grounding with little
or no effect.

I've tried ferrites on the cables to no avail.  Should I move the cable
modem from the Ham/Office location it would only bring it closer to the
antenna systems on the roof.

Today I contacted Comcast@home since I rent the modem from them and
requested that they change out the modem for another Manu/Model - They
agreed to do this on Sunday but could not shed any light on what Manu/Models
may be better - They also could not specify which Manu/Model they would
bring to change out.  One thing they did say is that they are phasing out
the model that I currently using!

At first the Comcast rep tried to get me to go out and buy a new modem to
swap - I didn't think that this was a good idea as I would be stuck with a
potential worse choice then what I currently have.

I'm hopeful that others may have been through this and have found a clean
modem to help steer me in the best direction with this.

p.s.  As of this morning, Comcast put out an email telling it 4,000,000
customers that they may be off line soon - No date and no time period for
return of service pending Excite filing Chapter 11 - Yuck! I have other
words for it that I can't use here hihi


Peter D. Vouvounas	Ofc: 732-701-1130
McLeod USA			Cell:732-674-4001
98 Meridian Dr.
Brick, NJ 08724
Mailto: wb3fsr@home.com
InterActive 2way: wb3fsr@imcingular.com