[Elecraft] K3S Audio buzz on transmit, especially AM

[Jim Brown]

On 4/26/2019 6:11 PM, Nicklas Johnson wrote:
> Plugging in some headphones, turning the TX Monitor up all the way, I don't
> detect the hum in the TX monitor signal either in TX test mode,
> transmitting into a dummy load, or even transmitting into the antenna with
> very low power.  If I turn up the Line In level, I just hear expected white
> noise on the TX monitor.  So at least as far along the path as the TX
> monitor, there's no hum or buzz introduced.

I'm confused, Nick. Under what conditions DO you hear the buzz? Antenna 
connected to the K3S?

> Switching the receiver (a KX3) to USB mode and using one leg of a
> buddistick as an antenna so I can walk around, the noise received around
> the house and outside is around S4 when transmitting about 100mW into the
> antenna, though it varies some as I walk around.

I'm more confused.  When you have been listening to your signal and 
hearing the buzz, HOW were you listening to it?  Were you listening on 
the KX3?   If you transmit 5-10W into a dummy load you should be able to 
hear your signal in a KX3 sitting next to it with NO antenna.

Does the buzz only happen when you're listening on the KX3 and there's 
an antenna connected to the K3S?  That brings up the possibility of 
passive intermod.  We'll talk about that after we've gotten the symptoms 
straight.

73, Jim K9YC