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Old 16th Mar 2019, 12:48 pm   #435
Radio Wrangler
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Default Re: Connectors made from exotic materials.

Quote:
Originally Posted by Craig Sawyers View Post
But you have to be a bit careful about saying that rf ingress has no impact on audio.

One particularly audible example is the zzt-zzt... sound from your speakers when your mobile phone does a station seek.

Now sure the RF level in those circumstances is pretty high, but nevertheless that is 800MHz or thereabout being picked up in cables and then demodulated by semiconductor junctions in the audio amp.
Craig
The effects of RF ingress are highly non-linear. With a watt or two from a nearby cellphone there is enough RF to turn on semiconductor junctions and to demodulate the amplitude of the pulsed cellphone transmission. The sound of GSM is familiar to most people.

However, lower levels produce disproportionately lower levels of effect once they fail to drive semiconductors into nonlinearity.

Meaning you get either a fairly obvious sound or essentially nothing.

The right fix is to have equipment with filtered ports which only allow what should be going in (remembering RF can enter via output connections.

There's my hifi in the lounge and a 200 Watt shortwave transmitter in the next room, and other transmitters up to 1296MHz, all at a lot more power than a phone. No discernible effects. No fancy cables. Just sensible design.

David
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