[aprssig] Re: Bob would be proud

Bob Bruninga bruninga at usna.edu
Sat Mar 15 21:49:18 EDT 2008

> We are trying to train some folks to use PSK31, 
> so we needed a radio simulator. ..

Yes, I use this in our "communication labs".  But I only use 10 10k resistors.  The audio output of every laptop goes via a 10k resistor to a single tie point.  That tie-point then goes back to the input of every laptop sound card.  In addiion, I pipe in live audio on another 10k resistor from an HF rig.

Then the students are all seeing what is on 14.070 AND they can all key up and join the fun and talk to each other too (though nothing goes back out on the air)...


--------original message------------
 We have a bunch of older laptops with sound cards and ideally, I'd like anyone in the room to be able to QSO with anyone else in the room.  What we needed was a 10 channel audio mixer.  Instead I went to the local dollar store and bought 10 el-cheap-o walkman headphones and 10 el-cheap-o computer mics.  I bound all 10 mics together by their stems with electrical tape, and placed them in one end of a cardboard box lined with foam.  I then cut one ear phone off each of the walkman headphones and shoved all 10 of them inside the foam lined box.  The foam stops echos inside the box that might throw off the phase lock on the PSK signals.  Each laptop gets one headphone cord and one mic cord.  I have a cd recording of 14.070, and I'll play that on one of the laptops.  It'll provide a base load of QRM and copyable signals.  Any of the laptops can go into TX mode and add their own signal to the mix.

There is a psk31 suite of programs that add a connected layer to PSK31 that is called Narrow Band Emergency Messaging System.  http://www.w1hkj.com/NBEMS/index.html 

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