Receiving computer detects and changes operating modem to match incoming message?


A couple of weeks ago I inadvertently transmitted a message during an NBEMS net with the operating modem set to one of the MFSK protocols instead of MT63-2KL.   Three or four people received that transmission and they all had the same experience:  their computers apparently recognized the incoming modem protocol and “automatically” changed from MT63 to MFSK.  We chalked it up to good experience but weren’t sure why it happened.  A ham with a lot more experience than me later explained that FLDIDI will automatically make this adjustment – i.e., it will change to match the operating modem of an incoming message when the and TxID buttons [top, right corner of the FLDIGI screen] are both clicked on. 


I tested this explanation and could not duplicate an “automatic” change by FLDIGI.  [Testing method explained below.]  Therefore I suspect there is some other configuration setting at work.  Any ideas or explanations would be appreciated!


Test set up:  Two laptop computers – one running Windows 7 Professional, one running Windows 7 Home Premium.  For these test I am not transmitting NBEMS over radio; just accoustic sound transfer between the two computers set across from each other on a table. Both computers running FLDIGI version 4.0.11 and FLMSG version 4.0.3.

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