[Elecraft] K3 AM operation with "FM" roofing filter?

[Eric Swartz - WA6HHQ, Elecraft]

Hi Dave,

The short answer is a 'qualified' yes. The wider FM filter can be used 
for AM transmit and receive, since the DSP limits the AM bandwidth, but 
there will be two issues.

1. On receive you will be subject to AGC blocking (de-sense) from nearby 
signals inside the 13 kHz FM filter's bandwidth but outside the DSP's AM 
bandwidth. (Typically those over S9+20 to 30.)

2. On transmit we will not guarantee that there will not be an increase 
in close in spurious signals inside the FM filter bandwidth. Normally 
the AM filter reduces any undesired transmit signals outside of its 
bandwidth.

So for casual AM listening, or AM transmission on a non-crowded band 
this might be OK. But we recommend the AM filter for any regular AM 
transmit usage.

73, Eric   WA6HHQ
Elecraft

Dave Lowenstein wrote:
> Does anyone know the answer to this?  Can the "FM" roofing filter be used
> when transmitting AM to save the cost of an additional filter for a
> rarely used mode?
>