[Elecraft] Advice on Additional Roofing Filters for K3

[Jim Brown]

On 12/24/2025 8:43 AM, Tom Bowles via Elecraft wrote:
> I'm considering adding a 1.8 kHz for SSB and a 250 Hz for CW, but I've read that the 250 Hz filter often measures wider in practice (around 330-350 Hz) and may not be as sharp as expected. Has anyone experienced this, and would you recommend it, or suggest alternatives like the 200 Hz or 400 Hz instead?

First, these are ROOFING filters to protect the DSP IF from overload 
from very strong nearby stations. It is that DSP that sets the IF 
bandwidth. I'm a serious contester, and have used K3s since 2008. The 
250 Hz 8-pole filter is great for CW. I found the 1.8 kHz filter too 
narrow for SSB, and prefer the 2.1 kHz filter. If you work RTTY, the 2.8 
kHz filter has much better response than the stock 2.7 kHz filter, which 
greatly reduces the incidental AM on transmit with RTTY. If you don't do 
RTTY, it doesn't matter.

73, Jim K9YC