Reported frequency wrong at 137kHz

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PA0O
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Joined: 2010/01/15 - 00:49
Reported frequency wrong at 137kHz

Hi om/yl
I am recently receiving 137kHz with the ICOM IC706

I make use of the CW 500Hz filter in my IC706.
WSPR at 137kHz to filter out the DCF39 signal at 0.1388kHz
Receiving (only) with the IC706 in position CW-narrow using the 500Hz CW filter is possible with these settings:

IC706 Dial: 0.137500 mode CW-R (for USB this must be 0.13600 to bring the audio in the center of USB filter)

WSPR: Advanced : Rx BFO (Hz) 570 (in my case) to adjust the audio at the correct frequency in the band. (1500 by default for USB mode)

WSPR Dial: 0.137000 Brings the displayed frequency ruler 400-600 meaning 0.137400---0.137600
not relevant Tx 0.137500 (no TX Txfr =0)

The decoding is good decoding traces as low as -31db

But there is a problem in the reported frequency.
The reported frequency is consequent 72Hz to high for all signs.
The trace position and frequency at the screen are correct.

F.i. PA0A = 0.137450 correct on the screen and also this is his correct TX frequency. But it is reported as 0.137522kHz
I change WSPR dial then the ruler will display him on the wrong freq. If i change WSPR Rx BFO to 500 f.i. then the position of the trace shifts to the wrong place and frequency.
And the reported frequency stays wrong +72Hz.
All other bands report the frequency same as it is displayed on the screen.
Only for 137 this is different and 72Hz off

Anyone having a clue?
73 Jaap PA0O