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Re: 2.4GHz QRM [was: ...Central States VHF Society Meeting]



My own experience with Wi-Fi and AO-40 indicates that Wi-Fi is relatively 
benign; it's the cordless phones that are the problem.

My Internet connection covers the last 3/4 mile with a Wi-Fi link.  The 
termination point at my house is aimed away from my satellite station, but 
to cover that distance (and through some trees) it has a hefty BBQ-style 
dish and a power amp, and the whole thing is less than 30' from my BBQ-style 
AO-40 antenna.

The system has been on various channels over time, as the operator has had 
to move things around to maintain the system, and to avoid another Internet 
operator in the area.  At one time I am sure it was on channel 2, but I 
never heard any interference on the AO-40 setup.  I did, however, hear the 
1-second clicking, and attributed that to someone with a cordless phone or 
similar device.  Turning off the Wi-Fi equipment didn't change the clicking.

We live in a relatively non-city setting (last subdivision as you head into 
the boonies).  So, as Wi-Fi spreads and grows, I am sure that we will notice 
an increase in the noise floor.  But from what I have seen, it's the other 
2.4 ghz devices that are the real annoyance.  Besides interference to 
Amateur Radio, they also interfere with Wi-Fi.  There's a corner in our 
building at work where a lot of folks use cordless headsets; can't get a 
good Wi-Fi connection in that area at all.

Greg  KO6TH


----Original Message Follows----
From: Bruce Bostwick <lihan161051@sbcglobal.net>
To: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] 2.4GHz QRM [was: ...Central States VHF Society  
Meeting]
Date: Sun, 30 Jul 2006 16:00:51 -0500

WiFi on channels 7 and above in the US is outside the 2.4 GHz ham  
allocation, if I recall correctly.  I can't recall how much channel 7  
spills into the ham bands but it isn't much.

Convincing the manufacturers to have their base stations either  default to 
a high numbered channel (say, 11) or concentrate their  "automatic" channel 
selection in 7-11 would help a lot, since most  people just take the base 
station/WAP out of the box, plug it into  their router, and go.  (How many 
wireless networks around you still  have the SSID "linksys"?)  It won't 
eliminate the QRM, but it will  help.  Especially if downloadable software 
updates can include this  behavior.  Some manufacturers are more cooperative 
than others ..  Apple used to use channel 1 as the default for their base 
stations,  and recently switched to 11 for current base station firmware.  
Not  sure if Linksys does the same or not.

Convincing individual users to stay out of channels 1-6 is likely to  be a 
lost cause, since there's not really any way to compel them to  do so.  
(Note, most of these people are the ones who a generation or  two ago would 
immediately begin harrassing the nearest ham if their  TV reception wasn't 
perfect, whether or not said ham was transmitting  on 6 meters or anywhere 
else.)

I suppose if the FCC decided to change the regulations governing WiFi  
devices, they could mandate channel allocations outside the 2.4 GHz  ham 
spectrum, but given their enthusiasm for BPL, I wouldn't hold my  breath.  
That's the nature of Part 15, folks ..

On Jul 30, 2006, at 9:52 AM, John Mock wrote:

>I ran into this problem with a 2.4GHz cordless phone at another ham's
>place in the countryside.  I could not hear AO-40 at all with a BBQ
>dish.  We caused it to select another channel, i think by pushing the
>relevant button, and the QRM went away.  I bet the same thing applies
>to wifi.  If/when we can get people at least to avoid using Channel 1
>(and perhaps those near it), that could at least mitigate the problem.
>Alas, that may not be very helpful in high density urbanized areas and
>requires cooperative neighbors (or, in the 'States, someone who can
>convince them that they are required to comply with Part 15).
>
>		    -- KD6PAG  (Networking Old-Timer, Satellite QRPer)
>
>P.S. Hmmm, i wonder what Hollingsworth has to say about all of this...

Heard from a flight instructor:
"The only dumb question is the one you DID NOT ask, resulting in my  going 
out and having to identify your bits and pieces in the midst of  torn and 
twisted metal."
----
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