[Elecraft] KX3: Cleaner audio with Yamaha CM500, also PTT

[Jim Brown]

On Sun,8/16/2015 7:17 PM, Brian Denley wrote:
> Don't electrets have to be powered (voltage applied) where dynamics do not?

Right.

On Sun,8/16/2015 8:00 PM, James Wilson wrote:
> Yes, the electret mics do require a small amount of power - Elecraft
> and others call it BIAS voltage.

It's called bias because it IS bias -- electret capsules have a very 
high output Z, so they use a FET follower as an output stage. The 
voltage provides bias for that output stage.

> Fortunately - with the K3 and K3S and very likely the KX3 also - that needed bias is available and can be turned on or off with a menu selection.

Virtually all modern rigs (within the last 30+ years) provide V+, 
usually about 8 V, on one pin of the mic connector. All it takes to use 
that for bias is a resistor in the range of 5K ohms from V+ to the mic 
input.

73, Jim K9YC