[Elecraft] RE50B microphone connected to K3

[Joe Subich, W4TV]

You want to keep pin one separate ...

Connect pin 3 to the "microphone return" in the transceiver
     (pin 7 in Elecraft/Kenwood transceivers)
Connect pin 1 to the chassis - the *SHELL* of the Foster mic plug
     in most transceiver.

If you do it right, you will use shielded twisted pair cable -
the twisted pair will provide a high degree of hum/RF rejection
and the shield will be the icing on the cake as K9YC likes to
point out.

Even though the transceiver mic inputs are not truly balanced,
treating them as pseudo-balanced inputs with twisted pair cable
and an isolated shield goes a long way to keeping things clean.

Manufacturers like Icom and Yaesu that use a coaxial lead (shield
is the return) for their microphone and then float the mic return
across the emitter resistor in the mic preamp or an RF choke are
asking for RFI and hum problems.  When some third parties then
recommend connecting the mic return to the shell of the Foster
mic plug with the cut-off component lead they compound the problems
by upsetting the bias of the mic preamp!

73,

    ... Joe, W4TV


On 2/4/2012 11:12 AM, John Kountz wrote:
> Has anyone had experience in tying pin 3 to pin one in an XLR connector to
> enable the transition from a balanced microphone to the unbalanced input of
> the K3?  In this regard I have used this arrangement to attach an
> Electrovoice RE50B to my K3 and, although I have made satisfactory
> contactswith this arrangement, I ask because many of you respondents appear
> experienced in audio and may have alternatives to making this
> interconnection.
> John Kountz, WO1S/T6EE
> 2 x K3s
>
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