| 
| 
MFSK Operation
_________________________________________________________
MFSK16 uses approximately the same bandwidth as 170Hz shift RTTY and so your MFSK16 transceiver settings can be roughly the same as those used for standard shift RTTY.
Transceiver Settings
Fine Tuning: If your transceiver is equipped with a "FINE" tuning feature, always use that for digital mode tuning once you have found the general area of the signals, however, most of your adjustments can be made in software, and not with the transceiver's VFO if you prefer. Some older rigs are really not stable enough for MFSK operation and will drift considerably off frequency.
USB: USB is the convention for MFSK operation in all bands. Either sideband can be used, but the sender and receiver must be using the same sideband, or one station must be inverted ( see: Inversion in the Configuration Topic).
Filtering: Optimum filtering depends on your transceiver's SSB filtering options and it's IF rejection characteristics. Wide filtering will enable you to work the largest spectrum without retuning your transceiver, but can also cause problems when there are strong adjacent signals. A narrow (RTTY or FSK) filter may help significantly with some radios and situations. Many transceivers do not have narrow filtering options while operating in SSB modes.
MixW Settings
Mode: Click on the mode box in the status bar and select MFSK. Then click on the mode box in the status bar again and select "Mode Settings".
TX and RX frequencies are set to the location of your cursor is in the spectrum window. Keeping this around 1500 Hz, will keep your transceiver operating close to the center of its pass band.
AFC, which should always be set to ON for MFSK operation due to the critical nature of MFSK tuning.
Squelch and the Squelch thresholdcan be adjusted to limit garbage characters, but you can also miss characters by using squelch as well.
The MFSK tones can also be inverted by checking the Inverted box. Note: This feature works differently in MixW than most other SoundCard digital programs, so please read and understand the information about inversion in the Configuration Topic.
Tuning MFSK
You can easily recognize the sound of MFSK once you have heard it. It sounds a lot like RTTY, only with multiple, rather musical tones.
The multiple MFSK tones are dispersed throughout the bandwidth of the signal while the two distinct Mark and Space tones of the RTTY signal are at the edges of the bandwidth. You can also see that MFSK16 uses just slightly more bandwidth than the standard 170Hz RTTY signal. To tune an MFSK signal, click the cursor in the middle, then adjust it to either side by using the CTRL- Arrow keys until you start receiving text in the RX window, and the AFC locks onto the signal. Because of interleaving you may find that it takes a little longer to tune MFSK than RTTY or even PSK. You will also notice that the RX text will come in batches instead of a steady stream.
Transmit:
To switch between transmit and receive press the Pause/Break key, click on the TX/RX box in the status bar, or select Options | RX, or Options | TX from the menu bar.
As with most of the other digital modes, It is possible to open multiple RX windows and switch the active window (the one you will be sending to) between them.