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Author Topic: SP-940 Speaker "hum"  (Read 756 times)
N2GEW
Member

Posts: 4




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« on: February 10, 2013, 09:09:56 AM »

Greetings, All:
I have a Kenwood SP-940 speaker in the shack and it accepts two audio sources and I have three radios I would like to connect. So I have a shielded RS cable from the two Icom radios on "A" and a JRC-535D with that same cable to "B". It seemed to work well enough, but now I am noticing some "audio hum" on the JRC receiver. Was it there before: I thought I eliminated it when I went to the shielded patch cables, but maybe not. When I disconnect the ICOM radio from "B",I don't detect any hum from the remaining radio.
If anyone has some experience here, I would appreciate knowing: is it possible the Icom and JRC have different polarity for the speaker hookups? Or a different matter?
Thanks,
Herb
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KA4POL
Member

Posts: 1907




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« Reply #1 on: February 10, 2013, 10:29:35 AM »

Audio is ground and signal. You might have a ground loop. You did not say which rigs you are using. If they are powered direct through high voltage two prong plugs it could be helpful to rotate one of them. If possible you could check one radio using a battery.
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KQ6Q
Member

Posts: 965




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« Reply #2 on: February 11, 2013, 12:22:47 AM »

The speaker audio on one or more of the radios might NOT be ground and signal - both sides might be hot to ground. Set things up so you're not connecting two radios with their audio output in parallel. you might want to make or buy a speaker selector switch that switches both wires.
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