[Elecraft] K3 Data Mode Transmit Issue

[Joe Barger]

The setup:

K3 with latest firmware.

Main Filters installed:
F2  2.7 KHz
F4  500 Hz
F5  200 Hz

F2 configured for all RX/TX modes
F4 and F5 configured for CW and Data RX

Configuration:
TX Test (no RF out)
Audio fed into line in (but no difference with mic input)
Line in set for "4 bars" ALC (but doesn't seem to make any difference how many bars)
Data Mode selected
Monitor turned up to comfortable level.

If F5 is selected as the RX filter, all is well.  But if either of the other filters is selected for RX and tones are transmitted, the tones have an audible "tick" with a frequency of (I'm guessing) around 40 Hz on top of the tone.  The frequency of the tick changes slightly as the frequency of the tone changes.  Audio input levels don't change the tick until the audio level approaches 0, then the ticks go away.  Modifying shift or bandwidth doesn't affect the tick.  Audio input signal is clean.  Change the RX filter back to F5 and all is well again.  Switch to USB and all is well with any filter.

My guess is there is something funny (a bug?) with the selection of the Data TX filter.

Anyone else have this problem?  Any ideas?

Thanks

Joe N6KK