[Elecraft] zero-beating a KX1

[Frederick Dwight]

If you do a google search on KX1 zero beat indicator or cw zero beat indicator you will see several circuits demonstrated.  Some like the one which uses the LM567 (non SMT) part and had 
a white LED seemed to be good, much less than 100 Hz BW and had the schematic, but some others seemed to be much too broad, perhaps hundreds of Hz wide. My circuit
needed quite a bit of audio drive, so rigged up a small 500-500 CT audio transformer and used the primary as a autotransformer to double the audio voltage
to the circuit which did not change the earphone volume but enabled the detector to operate without opening up the audio gain too much on any of my rigs.
          Good Luck   Rick  KL7CW

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