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Re: 2.4GHz QRM


434 MHz devices are quite a problem here. The ZL 
amateur 70cm allocation runs from 430 MHz to 440 
MHz and we don't the the luxury of the frequencies 
above 440 MHz for repeater use.

We have a nationwide system of linked 70 cm 
repeaters, and the management group for that 
system recently carried out the enormous task of 
adjusting and coordinating all the repeater input 
frequencies because of continued interference from 
the low power 434 MHz devices.

A diagram of the system can be found at: 

Wade down to page seven of this document for an 
explanation of the need for the changes:

But, Okay... this might seem acceptable, after all 
it's outside the space sub-band. Alas - my own 
experience has been that worst offenders by far, 
and the cordless headphones, mostly Chinese made. 
These transmit a wide band stereo FM signal and 
often seem to lack crystal control of the Tx. They 
not only wander outside the LP allocation, but 
through our satellite sub-band. I mentioned this 
in a discussion with an MSD official (=FCC) who 
laughed, and said they even wandered into 
commercial bands above 440 MHz and below 430 MHz.

If you don't yet have this problem, you are very 

Sil - ZL2CIA

Emily Clarke wrote:
> I'm a little concerned about the message here - are you saying that 
> RFICs in 434 MHz will encroach on our allocation in 435-437?  These are 
> minuscule power devices (since, for example, sitting on the freeway I 
> don't want to get warnings about the tire pressure of another Volvo 1/2 
> mile away.) So before I get all bent out of shape by this can you 
> provide some credible data or (ugh) statistics that it will have any 
> real impact in the next 20 years?
> 73,
> Emily
> At 05:55 PM 8/1/2006, you wrote:
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