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Author Topic: By-pass capacitors / XLR cables  (Read 2517 times)
N9NLU
Member

Posts: 6




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« on: February 03, 2013, 05:18:39 PM »

Simple question ...

I'm looking to install by-pass capacitors on my XLR audio cabling due to 80m & 60m RF getting into my transmitted audio.

I would be using three .001uf disk capacitors -- one cap on pins 1&2, one cap on pins 2&3 and one cap on pins 1&3

Should I install the capacitors on one connector of each cable - the XLR connector leading to the input of the device being connected.

OR

Should I install the capacitors on BOTH connectors of each cable

Thanks in advance

Dave / N9NLU

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AA4PB
Member

Posts: 13032




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« Reply #1 on: February 03, 2013, 05:50:35 PM »

I'd place the capacitors closest to the device that is receiving the signal.
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W9CN
Member

Posts: 46




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« Reply #2 on: February 04, 2013, 08:27:38 PM »

There could be several things going on here that adding caps may or may not fix.  Depending on what you are plugging those XLR cables into you might be suffering from pin 1 design problems (google search pin 1 RFI issues) where the device designer routed the pin 1 ground lines incorrectly causing the RFI on the ground line to contaminate the analog circuitry. 

This is a pretty common problem with inexpensive gear and caps on the XLR's won't fix it.  You can also have issues with inexpensive mic cable not having sufficient braid or it wrapped tight enough to give you sufficient shielding to keep the RFI out. 

And the female XLR that you connect to the mic should have the connector shell lug tied to pin 1 in high RF fields..

Stuffing caps on the XLR connector won't hurt but don't be surprised if it doesn't cure it.

I am assuming that you have a solid ground to your transmitter/transceiver/amp/power supply/tuner/coax/feed line also..

 
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