Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Cable modem RFI  (Read 1704 times)
K6AQ
Member

Posts: 20


WWW

Ignore
« on: January 08, 2013, 09:52:32 PM »

I have a Motorola SB6141 cable modem about 5 feet away from my Yaesu FT-450AT. Unfortunately, it seems to be contributing to about 2 S-units of noise on at least some of 40 meters when powered. I replaced the wall wart with a direct connection to the shack's 12V supply with no change, as well as placed snap-on ferrites on almost all of the wires coming out of it except for the coax feed. I'd put a choke on the coax feed too, but the modem's status page said that it was using 28MHz for uplink, so it's probably not a good idea.

Is there anything else I can do besides going without Internet while on the air? (My setup is already pretty marginal as is due to being HOA restricted in a condo, so I'd like to try to improve my S/N ratio as much as possible.) Also, would something like the ANC-4 help?

Thanks!
Logged
WA7BBI
Member

Posts: 17




Ignore
« Reply #1 on: January 11, 2013, 12:18:18 PM »

Go ahead and try the choke on the cable. Snap on ferrites should only affect Common Mode radiation and not the Differential Mode (ie. the 28 MHz signal). You have nothing to lose. Good luck.

Jim, WA7BBI
Logged
WB4SPT
Member

Posts: 135




Ignore
« Reply #2 on: January 11, 2013, 02:00:06 PM »

This is not a wireless, right?  If the coax choke doesn't do it for you, make an aluminum foil case for it, wrapping a couple of turns around and crimp close to the wiring.  If it's direct chassis radiation, at least you will find out.  If it needs to stay, then decorate it. Grin
Logged
N4NYY
Member

Posts: 4742




Ignore
« Reply #3 on: January 12, 2013, 12:31:26 PM »

I have a Motorola SB6141 cable modem about 5 feet away from my Yaesu FT-450AT. Unfortunately, it seems to be contributing to about 2 S-units of noise on at least some of 40 meters when powered. I replaced the wall wart with a direct connection to the shack's 12V supply with no change, as well as placed snap-on ferrites on almost all of the wires coming out of it except for the coax feed. I'd put a choke on the coax feed too, but the modem's status page said that it was using 28MHz for uplink, so it's probably not a good idea.

Is there anything else I can do besides going without Internet while on the air? (My setup is already pretty marginal as is due to being HOA restricted in a condo, so I'd like to try to improve my S/N ratio as much as possible.) Also, would something like the ANC-4 help?

Thanks!

I had a friend that had a similar problem and he shielded it using a metal case and grounding it. The problem is that I cannot recall if it solved it. It was a while ago. I suppose it would be cheap enough to give it a shot.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!