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I just upgraded to the 027 firmware on my QMX, from 018. Being able to select the CW filter is very nice, but I don't understand how to enable cascading or compounding of two CW filters.? The manual says there are two CW filters - 300 and 500 Hz, yet the submenu shows 8 filters, ranging from 50 Hz to 500 Hz.

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Thanks and 73,

Steve, N2IC

Hi Steve

It's tricky to get your head around.? I thought I understood it but I really didn't until I watched this great video- recommended, I'm sure it will help.

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73?

Peter GM0EUL

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Thanks. I watched N2DI's video. It still doesn't explain how to cascade two 300 Hz filters, centered at 500 and 650 Hz, which is the example shown graphically in the manual.

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73,

Steve, N2IC

Steve, I believe the cascading happens automatically.? You just choose your passband then choose your center frequency and the software chooses the two filters for you.? The idea is the software prevents ringing using this method rather than a single filter which does cause ringing.

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Joshua

Before Joe N2DI's explanation, I was also confused. Yes, the cascading is automatic, depending on the passband and center freqs you select. The part of Joe with a great chart that helps make decisions on which filters are useful with which settings.? After that watching that a couple of times, the actual filter selection works great. Beware... listen to the explanation AND the chart.

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72 de N4REE, Bob Easton - QRP CW forever

This great response from N2DI clarified it all for me and squares up with KJ7LVZ's reply.

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@JoeN2DI There are only two filters: 300Hz and 500Hz. All the other filter widths are made by stacking the 300Hz and 500Hz filters, so when you select anything other than 300Hz or 500Hz, you’re cascading the 300Hz and 500Hz to make that value. Does that make sense?

After playing with CW filters, I have a few comments...

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When a single (not cascaded/compounded) 300 Hz or 500 Hz filter is selected, the ultimate rejection is not great. I can still hear a moderately strong station, 2 kHz away.? However, selecting a 400 Hz filter, which internally cascades 300 Hz and 500 Hz filters, results in excellent ultimate rejection.

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It would be nice to be able to select a lower center frequency. Personally, I prefer 400 Hz.

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73,

Steve, N2IC