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Author Topic: WiFi interference on 144.390  (Read 5841 times)
WX7K
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Posts: 45




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« on: October 12, 2011, 05:17:24 AM »

I am trying to set up a fill in digi and a Wx station and am having a problem with my WiFi setup.  I have a D-Link router and I am getting a high noise level on 144.39 while the other freqs in my memories are normal noise levels.  For instance on 145.41 I get about two bars, 146.76 I get two bars, on 146.58 simplex I get three bars, but on 144.39 I get 8 bars and my squelch will not cut it out, even when cranked full clockwise.  When I turn the router off or disconnect the antenna the noise goes away.

I am using a Kenwood 231, Kantronics KPC3+, a J-pole antenna on the roof about 12 feet over my head, and as I said before a D-link router about 3 feet away.

Why that one freq?  What can I do about it?  Am I doomed?

Thanks

Newell
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W8JX
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« Reply #1 on: October 12, 2011, 07:03:18 AM »

Try a different router brand/model. You are likely getting interference from the cpu side of it. It could possibly be the power adaptor but my gut feeling here in hardware. A router has a cpu and memory that allows it to do routing functions and can emit RFI at vhf and uhf frequencies
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Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
AA4PB
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« Reply #2 on: October 12, 2011, 07:45:42 AM »

As in most RFI problems the first job is to determine how the signal is exiting the box and what is acting as an antenna and radiating it.

Do you have any computers connected directly via CAT5? If so, disconnect the CAT5 so that only the wireless connection is active.

Disconnect the WAN side and/or turn off the modem while leaving the router running. The goal is to determine if the RFI is being radiated by cables or if it is comming directly out of the case.

Try winding DC power cord around a ferrite core located close to the router. The goal is to choke off any RFI that might be coming out and being radiated by the power cord.

Move the router farther away from the radio and antenna. Separation is a great attenuator.

J-pole antennas often have issues with common mode currents flowing on the coax shield. Its possible that the RFI could be following the shield up to the antenna. Try a choke (coil of coax) up close to the antenna.

Last resort - a different router.
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W8JX
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« Reply #3 on: October 12, 2011, 08:34:23 AM »


Last resort - a different router.


Given nature of his problem I would change router brand first. I have 1 Netgear wireless router and 2 Netgear wireless access points here and never had any RFI issues with any one them on any band.  
« Last Edit: October 13, 2011, 07:44:55 AM by W8JX » Logged

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Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
AA4PB
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« Reply #4 on: October 12, 2011, 01:40:11 PM »

The only reason I say "last resort" is because he may not have another router available. That means you have to go out and purchase one and you may not be able to return it if it doesn't fix the problem. I also don't know how familiar he is with configuring the router. It may or may not be a big issue for him.

I'm just suggesting that he get a reasonable idea that it is the router itself that is causing the problem before going through the trouble and cost to replace it.

Another idea is to set a 2M HT on the frequency (maybe remove the antenna) and use it as a wand to see where the majority of the RFI is comming from.
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WX7K
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« Reply #5 on: October 12, 2011, 05:27:35 PM »

I have already done some of the things suggested, and will try the others.  Using an HT as a sniffer is not one I thought about.  I really don't want to buy another router, but if I need to.......... it is only money, after all.   Grin  As far as setting it up, no problem.  I have already made most of the dumb mistakes.  I'll let you know what I find out.

Tnx.

Newell
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WX7K
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« Reply #6 on: October 13, 2011, 10:32:03 AM »

Well, I disconnected each line on the back of my modem one at a time and the only one that made a difference was the WAN connection.  The noise went away. I get my broadband via a wireless provider and the radio signal from the provider was still active so I think I can eliminate that.  So it would appear that the nosie is coming from my router only when the internet feed is applied.

I did not have much time this morning before work to do more, but the question now is: can I filter out the noise or do I need to get the new router. When I disconnect the antenna from my radio the noise goes away.  So the hash from the router is coming in on the antenna.  I already have a ten turn choke in my feed line at the antenna.  Does that mean the noise is coming in on the feed line inside the house and not from the J-pole iself?  The power line to the router runs right along the antenna feed line so I will try a ferrite choke on the power line to the router next. 

Have i missed anything?  Any other suggestions?  I appreciate all your suggestions.

Tnx

Newell
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KJ4OBR
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« Reply #7 on: October 13, 2011, 12:31:36 PM »

Try replacing the cat 5 from your modem to the wireless router with a good high quality shielded patch cable. The manufacturers supplied patch cables are the cheapest that they can get. Good high quality shielded cat5 might help.

73
Dave


Well, I disconnected each line on the back of my modem one at a time and the only one that made a difference was the WAN connection.  The noise went away. I get my broadband via a wireless provider and the radio signal from the provider was still active so I think I can eliminate that.  So it would appear that the nosie is coming from my router only when the internet feed is applied.

I did not have much time this morning before work to do more, but the question now is: can I filter out the noise or do I need to get the new router. When I disconnect the antenna from my radio the noise goes away.  So the hash from the router is coming in on the antenna.  I already have a ten turn choke in my feed line at the antenna.  Does that mean the noise is coming in on the feed line inside the house and not from the J-pole iself?  The power line to the router runs right along the antenna feed line so I will try a ferrite choke on the power line to the router next. 

Have i missed anything?  Any other suggestions?  I appreciate all your suggestions.

Tnx

Newell
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AA4PB
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Posts: 12700




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« Reply #8 on: October 13, 2011, 03:02:42 PM »

I'd try moving the ISP wireless modem and the router to another location in the house and see what that does.

The noise *could* be generated by the wireless modem rather than the router. It may go away when the router is disconnected and the ethernet port on the modem shuts down. It could also be the other way round - noise generated by the router stops when the router ethernet port shuts down. You can make the port come up by plugging into any live ethernet connection (computer, switch, etc) to see if that causes the noise to come back.

The shielded CAT5 is a good idea as is using some ferrites one the cable. I'd buy a new router in a second if I was pretty sure that would fix the problem. I'd hate to start randomly buying routers only to find out it was not the problem.
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KC9XG
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« Reply #9 on: October 17, 2011, 11:01:01 AM »

I have seen similar interference in the VHF range caused by Ethernet cables.  A 100 mbs square wave can wreak havoc on nearby receivers.  Changing Ethernet rate from 100baseT to 10baseT solved several problems I have observed.    If lowering the rate is not an option, then shielded cabling may be the only course of action likely to resolve this type of interference.

Bill KC9XG
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KA6MLE
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Posts: 78




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« Reply #10 on: October 27, 2011, 12:07:53 PM »

You may not need to change anything if you set your CD (Carrier Detect) to SOFTWARE. As the KPC3+ manual states:

If set to Software, the firmware inside the TNC will detect the presence of data to enable the carrier detection, allowing operation with un-squelched audio.

I run my digi in this mode and even if there is noise present, it works just fine

Jim
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AA4PB
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Posts: 12700




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« Reply #11 on: October 27, 2011, 12:38:07 PM »

Software carrier detect will keep noise from generating false signal detection on the TNC, but it won't prevent the noise from interfering with incoming valid packet signals if it is strong enough. It's primary value is permitting you to run with the squelch open on your receiver so that you can detect weak signals that might not be strong enough to open the receiver squelch.

You really need to eliminate the RFI if you want to get maximum performance from the TNC.
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KC2MMI
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Posts: 621




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« Reply #12 on: November 02, 2011, 12:55:56 PM »

Cablemodem or DSLmodem?

I had a similar problem with a Linksys that simply had to go. If the router was built cheap, as most are, it can put RFI on the cables and there's no way to get rid of it. Put the router in a tin box and the cables still radiate the RFI.

With a DSLmodem there's nothing to be done on the WAN side since you are going into unshielded phone lines. With a cablemodem, there's a chance that moving it to another location will help, since the cabletv lines are shielded. And sometimes the cable company can come in and upgrade the grounding or check for bad connections that are contributing to the problem.

But the odds are? Time for a new box, test it out within the return period and return it if needed.
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