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Author Topic: DSL & Wireless Routers  (Read 3560 times)

Posts: 1

« on: June 04, 2003, 08:04:41 AM »

I installed DSL this past weekend and use a 2.4GHZ wireless router from LINKSERVE to connect the 2nd computer upstairs.  I have a strong carrier on 14.215 and other RFI noticeable on the receiver.

Has anyone experienced similar RFI using DSL and a wireless router ?

Is it the modem or router ?

I have contacted both vendors and will see what the techinical reply is.


Posts: 5


« Reply #1 on: June 07, 2003, 07:46:36 AM »

Well, I have about the same problem with my cable modem LanCity. Maybe you are lucky with having a short ground path and  finally succeed in grounding your system. I don't, the shortest path to the ground is two flat long.
There is a lot of rectangular-like signal going in and out of these devices resulting in a wide spectrum RF noise.
Perhaps radio is using a common ground with the devices or a common outlet, try to change this, situation will improve a bit. Keep it as far as possible.

Posts: 229

« Reply #2 on: June 07, 2003, 11:38:15 PM »

ADSL occupies spectrum between .1 and 1.1 MHz or so, and shouldn't be a  problem for us at Amateur frequencies. However, the digital devices that process it can be.  I worked recently for a company that was designing and making the telco end of the ADSL lines, and I remember the specification for one of the modems; 20 dB *below* the FCC's emission limits.

Well, that's not a recipe for profit -- though it is radio friendly -- and I'd not be surprised if others were not so concened about interference.  That may fix itself; in my experience, a digital device which radiates a lot also tends to be more susceptible to transients and RF ingress.

In any event, although you say you've filtered the power, I suspect the filter you are using is more a differential mode than a common-mode filter, and such problems are usually due to common-mode currents. One problem I saw with such a modem went away when I lifted the wall-wart's safety ground. The CURE would have involved beefing up common-mode powerline filtering in the modem, which was not ours to redesign, but you get the idea.

Another possible problem is digital inputs and outputs. Many I/O's are unfiltered, so onboard sources radiate (again, as common-mode noise) from cables conected to them. It may be possible to use better built shileded cables to confine this to the computer and peripherals. Or you can use several turns of I/O cable in a fairly high permeability ferrite to choke this off. One problem with relying on shielding is, all peripherals connected must be good enough to keep the noise confined.

I'd take a small portable receiver and check around the ADSL equipemnt, AND your own computer, to see where the interference comes from. You may find that it's been there all along and only shows up when you attach and run your router.

Good luck.


Posts: 1

« Reply #3 on: June 09, 2003, 01:31:58 PM »

Well,  I found 14 ft piece of shielded twisted pair with RJ45 jacks on both ends.  When I connected this to the LInksys Wiresless Accesspoint router and to the computer card that comes with it....the carriers went away.

However, there is still some other types of white digital sounding noise around.  It may be the combo tv/vcr upstairs which I will check out



Posts: 69


« Reply #4 on: June 11, 2003, 09:27:45 PM »

I'm using a LinkSys WAP11 802.11b wireless access point, and a BEFSR41 router.  (Separate units.)

When I installed the WAP, several months after buying the router, and before LinkSys made a dual-purpose unit available, I noticed a nasty birdie on 450, but only in the room with the WAP.  

It seemed to move around quite a bit (I used my TH-F6A's "panadaptor").  I'm not sure if it was moving around, or the WAP was just changing channels, because sometimes the problem was there, and sometimes it wasn't.

(I ended up putting the WAP up in the office instead of having it in the family room near the notebook.)

Up in the office, it was worse....   No idea why, but it ate any hope of listening on that band with indoor antennas.  That's when I decided that the power feed (from a wall wart) and the CAT5 wiring might like some ferrite.  I grabbed a couple of RS "clip-over" ferrites and _most_ of the noise went away.  The TH-F6A still has problems near the WAP, but the older TH-77A no longer notices the WAP at all.

(The TH-77A specs similarly to the TH-F6A if you're not familiar, but it's basically not a "DC-to-Infinity" receiver.  Extended "ham band only" on 150mhz and 450mhz.  Bigger than a breadbox compared to the TH-F6A, too [grin].  I'm guessing that the F6's wider front-end is letting the birdies in more efficiently.)


Posts: 5

« Reply #5 on: September 24, 2003, 04:49:40 PM »

I have a Kenwood TH-F6a and a SMC Wireless Routers in my living room. Oh boy! I noticed how much RFI my Wireless Router gives when I'm just scanning through the HAM Bands;especially on 2 and 440 meters. The only solution that worked for me was to put the Wireless Router at the highest point point in the ceiling with the antenna side of the router pointing up. I still get some interference but not as much as when I had it low. You can also move it to another point in your house or apartment away from your ham rigs since the signal doesn't penetrate that far untless you have a wireless signal booster.
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