[Elecraft] K3 RX Audio Roll-off below 400 Hz

[Joe Subich, W4TV]

 > Is this roll-off similar to what other folks are seeing?

That is slightly less roll off than I see with either the FM (13 KHz)
or 2.8 KHz filters in the data modes.  It is in line with the 200 Hz
cut off for data modes.

In LSB/USB the low cut is less steep.  In SSB it looks to be about
10 dB per octave below 300 Hz (-10 dB at 150 Hz, -20 dB at 75 Hz,
-30 dB at 40 Hz) vs. 0.2 dB/Hz below 250 Hz in DATA modes.

73,

    ... Joe, W4TV


On 9/7/2013 11:55 AM, Bob wrote:
> My K3 is in the 61XX serial number range (almost 2 years old), and I'm
> running FW 4.67/2.81.
>
> While setting up WSJT-X, I've noticed a rather pronounced audio roll-off on
> the waterfall display.  By other means I've verified that the sound card
> being used is flat down to below 20 Hz, so it isn't that.  Assuming that it
> is an attribute of the K3 itself, things are flat down to 400 Hz.  Then
> there is a -3 dB roll-off at 300 Hz, -10 dB at 200 Hz, and -20 dB at 100 Hz.
>
> At the moment, my widest filter is an 8-pole 2.8 KHz (A 6 KHz AM filter is
> on order), and it properly centered and wide open.
>
> Is this roll-off similar to what other folks are seeing?
>
> 73, Bob, WB4SON
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