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Re: [Fwd: threat to 2.4 GHz.?]



Hi, Robin,

This is now an old issue.  Here's how it plays out.

The cordless phones, microwave ovens, and other types of non-licensed 
emitters share the band with other, licensed stations, including amateur 
service and amateur-satellite service stations.  (That's us!!)

If you look at the Table of Frequency Allocations, you'll see that the 
amateur service and the amateur satellite service get to use all or part of 
the band.  Having an entry in the Table gives precedence over all other uses.

What does this mean in somewhat over simplified and practical terms?

First, stations NOT operating in accordance with the Table and industrial, 
scientific, and medical (ISM) devices MUST ACCEPT all interference from 
stations operating in accordance with the table.  So, if a cordless phone's 
operation is interrupted by an amateur station, the cordless phone operator 
must accept the interference.  (Stop laughing.  We'll come back to this later.)

Second, all stations operating in accordance with the table can claim 
protection from ISM devices and stations NOT operating in accordance with 
the table.  So, if a cordless phone causes interference to an amateur 
station, for example, the amateur station operator can ask that the 
cordless phone be adjusted or shut down to eliminate the interference.

That is, essentially, what the radio regulations say on the 
subject.  Domestic rules and regulations implement this in each country.

Now, we have to get really practical and follow the money.

Here in the USA, we have seen interest on the part of cordless phone 
manufacturers on obtaining some protection from amateur 
stations.  Why?  They're making a bundle selling this neat boxes to 
millions of households.  Ask yourself: Do they want to take the risk of 
customers being told that their local ham is blameless and that they, the 
phone owner, are at fault and have to turn off their brand spanking new 
cordless whizbang phone/answering machine/speaker phone/automatic coffee 
percolator because it is interfering with a ham station?  Of course not, 
the treaty and law and rules and regulations notwithstanding.  That 
whizbang cost a lot of money!

As ISM and low power use of our shared bands increases, we need to be 
prepared to deal with this kind of problem more frequently.  Fortunately, 
the FCC got the last such request right and quoted 47 CFR Part 15 which 
implements the Treaty.

How long will this last?  I'm not smart enough to know.  But, you can see 
how and why we need to be diligent guardians of our allocations.

Hope this helps.

73, art.....

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