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Interface Toughbook Mic Input to Line Out from SWL's PSK20
I want to interface the audio from the Small Wonder Labs PSK20 to the
mic input in the Toughbook CF27 laptop. The computer has no line input, and I plan to use the mic input via the port replicator. The Toughbook reference manual doesn't give any specs for the mic input. The user manual does contain this caution: "Use only a monaural condenser microphone (miniature jack). Using an input source other than a monaural condenser microphone may not allow audio to be input or may damage the equipment." Reading suggests that an L pad in the 40-60 dB range is required, but I would like to narrow this down before experimenting. Any experiences using the Toughbook on PSK would be helpful. Thanks, Tom, N3IJ |
#2
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Interface Toughbook Mic Input to Line Out from SWL's PSK20
"Tom, N3IJ" wrote in message ... I want to interface the audio from the Small Wonder Labs PSK20 to the mic input in the Toughbook CF27 laptop. The computer has no line input, and I plan to use the mic input via the port replicator. The Toughbook reference manual doesn't give any specs for the mic input. The user manual does contain this caution: "Use only a monaural condenser microphone (miniature jack). Using an input source other than a monaural condenser microphone may not allow audio to be input or may damage the equipment." Reading suggests that an L pad in the 40-60 dB range is required, but I would like to narrow this down before experimenting. Any experiences using the Toughbook on PSK would be helpful. Thanks, Tom, N3IJ Microphone does work well if you have a decent one. Also has the advantage of being able to record both sides of conversations for logging purposes. The inputs are usually 500-2000 ohm impedance and have a DC bias for powering the mic. I have always used what is in the junk box to make the transition. The speaker output is fed to a low impedance audio transformer. It may be 8 ohm to 2000 ohm or 500-500 ohm or whatever in that range. Such things are easily obtainable at RS and other sources. The output of the transformer is loaded with a resistor of 1k-10 k and a series resistor of 100k or more feeds the mic input. This will usually reduce the input to mic level and the transformer will break up any common mode potentials between the chassis of the computer and the radio that tend to bring hum and noise. You will also see a flatter response than with acoustic coupling. You should be able to reduce the mic level in the mixer applet to normal level. You may have to play with the 100k and may need to shunt the mic input as well but you will find this by experimentation to get it right. A purist might also series the input with a 1uf to 10 uf capacitor to completely block the DC component but the series 100k should limit that sufficiently. Some experimentation could be done for more precise equalization if you still have time on your hands. This should work with any sound card mode. |
#3
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Interface Toughbook Mic Input to Line Out from SWL's PSK20
On Nov 27, 11:35*am, "Tom, N3IJ" wrote:
I want to interface the audio from the Small Wonder Labs PSK20 to the mic input in the Toughbook CF27 laptop. The computer has no line input, and I plan to use the mic input via the port replicator. The Toughbook reference manual doesn't give any specs for the mic input. The user manual does contain this caution: "Use only a monaural condenser microphone (miniature jack). Using an input source other than a monaural condenser microphone may not allow audio to be input or may damage the equipment." Reading suggests that an L pad in the 40-60 dB range is required, but I would like to narrow this down before experimenting. Any experiences using the Toughbook on PSK would be helpful. Thanks, Tom, N3IJ What I ended up with is an L-pad with 10K in series with the input and 100 across the output. This is supposed to be a 40dB pad. I may need something in the high 30s instead of 40, because to get a satisfactory waterfall, I need to max the mic gain in Windows 2K. Tomorrow I'll get a 5K pot and connect it in series with a 5K resistor in place of the current 10K resistor. 8-9K might be where I need to be to have the Windows level control somewhere in the middle of its range. Thanks to all for the suggestions. Tom |
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