Soundcard Isolation Project - VA3CR

7.5.4 Other Strange Audio Being Produced by Your Signal - these sounds may be
recognizable, like music or voices from the shack, or strange audio tones moving up and down
the band, or PC sounds like Windows alerts.
• Voices, music or other sounds from the shack is getting into the mic of the
transceiver. Some rigs have their microphone active when using the accessory port.
Disconnect the microphone.
• Another microphone is on your PC, sometimes mounted in the monitor. Mute the
sources as described in section 7.3.1 and 7.4.1 above.
• Weird tones moving around like a slow sawtooth oscillator are caused by RF getting
into unused inputs on the Sound Card. Section 7.3.1 and 7.4.1 again.
7.5.5 Break Up of Your Audio When Transmitting - gaps in your transmitted signal when
sending data. You may also notice that the PTT light goes on and off while transmitting.
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Other programs on your PC are stealing too much time from the sound card
program. De-activate the other programs, or get a faster PC
Bad connections in the interface, check soldering on all joints on the circuit board.
Bad connections in the audio cables or in the rig control cable
Transceiver problems
7.6 Filtering the Audio Cables - most problems which are RF related are cured by using the
isolating interface described in this design document, using shielded cables and grounding the
system properly. But there are some tough environments that still manage to get RF into the
sound card system through the “Line In” cable.
Some success in curing this has been found using ferrite beads on the audio cable just before it
plugs into the sound card “Line In”, Same idea works on the audio line going into the rig too.
Two sources for ferrite beads are Amidon and Palomar-Engineers.
Amidon
Palomar-Engineers
www.amidoncorp.com
www.palomar-engineers.com
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