Re: CW Noise Pedestal


I believe the excess fan noise problem was eliminated with a capacitor across the fan drive lines. There’s a mod kit for the K3. It should already be present in the K3S. 

There is of course a pedestal within the TX crystal filter passband, but it should be down quite far in relation to either voice or CW keying bandwidth. 


On Jan 12, 2020, at 12:19 PM, Rob Sherwood <rob@...> wrote:

K3 fans.  N0QO and I found the problem when monitoring a K3 using a Perseus direct sampling receiver as a spectrum analyzer. 

The noise pedestal was inside the 2.7 kHz or 2.8 kHz roofing filter that is in the circuit on transmit.  The skirts of the roofing filter make the noise fall off rather quickly. The fans have either 3 or 4 speeds, and the noise pedestal gets worse the faster the fans spin. 

I don’t know that this is your problem, but I thought I would mention it since it isn’t a widely known issue 
Rob, NC0B

On Jan 12, 2020, at 12:29 PM, wb6bee <wb6bee@...> wrote:


Are you thinking KPA1500 fans (or K3s fans)


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