[Elecraft] PSK Microphone input

[Andrew Catanzaro]

Ralph,

Put the resistor between pins 1 and 6 in the *plug* for the 
Heil Proset, rather than in the radio.  That way the Rascal interface works, 
and no blocking capacitor is necessary.  Another advantage is that
you can use other microphones that don't require a bias voltage with
the K2.  The Heil dynamic elements still sound significantly better
than the electret elements in the MH-2 (discontinued) and Heil
Proset boom microphone, although the K2 output is somewhat less.
When I use the K2 with a Heil HC-5 element and a linear RF amplifier,
I get the best audio reports.  The Proset is still useful for Field
Day and other operations away from home.

Although there are published pre-amp circuits for using low-output
dynamic mikes with the K2, it isn't clear to me why it wasn't
designed with higher audio gain to start with.  That way higher quality microphones
could be used.  The K2 is capable of quite high quality transmit
audio, but it isn't as apparent with the electret microphones. Icom et
al have made the break with electrets starting with their Pro II and later
rigs.  We are still using the equivalent of the older style Icom mikes.

Andy W9NJY
Milwaukee
K2 2651 
KX1 1139