Using "7FSK"

This experimental mode was suggested by Rik Strobbe, ON7YD as a means for speeding up DX QSOs by using multiple frequencies within a narrow band to represent the letters and numbers required for a QSO. Each character is represented by a two-tone sequence within the 7 tones of the system. This gives 49 possible characters.

It is fairly easy to receive using a Spectrum display program such as Argo but transmitting it is not so easy. One method, developed by Marcus, DF6NM, is detailed below:

Subject: LF: SpecLab generates DFCW, QRSS and 7FSK

Hi SpecLab co-users,

Wolf's powerful program has a built-in terminal for digital modes for an SSB transceiver. One of them is a Parallel-Multitone Hell modulator, which generates tones from the typefaces of text entered into the terminal. Combined with a font editor (e.g. Softy by D.W.Emmett), this becomes a universal tool to play with visual modulation schemes.

The resulting tones are individually phase-coherent and can be soft-shaped to avoid clicks.

For narrowband DFCW, I have prepared a font consisting of two lines of dashes and gaps. To use it, you have to copy the .fon file to the Windows\Fonts directory. After starting SpecLab and the digimode terminal, you can choose "DFCW" and enter Size=1 in the Settings / Select HELL font menu. In Digimode Configuration, you select Parallel MT mode and then set Symbol Rate, TX Center Freq and FSK shift.

For example, a symbol rate of 0.05 baud gives 3*20s dashes and 20s intervals. The dash and dot frequencies are related to the settings as shown below:

f_H=CF+ FS * 4/8 and

f_L=CF+ FS * 3/8,

e.g. CF=1422 Hz and FS=0.8 Hz produces 1422.4 / 1422.3 Hz tones.

An output level of 800% will give full scale DAC output, and the Symbol shaping time can be set for smooth edges (e.g. 20%).

After you have pressed TX, any text entered will be sent to the audio output.

Please don't look for all the special Morse characters, "sk" can be sent by typing # . Normally, the audio input and waterfall is automatically disabled during transmission, but you can reactivate it for duplex mode by clicking on the Sound-In box in the SpecLab Components diagram. To see your own signal as well, you may have to set up an analog loop by enabling Wave input in Windows' recording mixer.

The other fonts are for CW/QRSS and the new 7FSK mode. For CW, simply set FS to 0 and CF to the desired audio note. The 7FSK freqs are f7=CF + FSK * 4/8



f2=CF - FSK * 1/8

f1=CF - FSK * 2/8,

e.g. CF=2289.85 and CF=1.2 above 135500 Hz zero beat gives Andy's set of frequencies.

I have decided to add an extra space after each 7FSK pair. This does slow down the mode by a third, but it allows easier synchronization for the RX as well as QSK to watch between characters on the TX site, and it gives the PA a rest.

Tnx agn to DL4YHF for SpecLab.

Happy experimenting

de Markus, DF6NM


Here is Marcus' Font file.

So thanks to Markus and Wolf we can send the mode but to receive it you'll need Rik's table of character coding so you can read the message off the Argo screen.

Andy's test

This is what it looks like on a Spectrum display. The "60" in 7fsk60 refers to the duration of each "dot" (60 seconds). Thus each letter takes 2 minutes to send at this speed, as fast as a letter "e" and its space but 10 times faster than a "0" (zero) in Morse.

In the screen shot above, tone 1 is at the top of the screen with tone 7 at the bottom. Some receivers will output the signal with them the other way round. Tone 1 is in fact the lowest RF frequncy.

Here is Rik's table of suggested codes representing the necessary characters for a QSO. There are some spare ones for future additions.

 1 1=A  2 1=H  3 1=O  4 1=V  5 1=0  6 1=7  7 1=space
 1 2=B  2 2=I  3 2=P  4 2=W  5 2=1  6 2=8  7 2=rprt O
 1 3=C  2 3=J  3 3=Q  4 3=X  5 3=2  6 3=9  7 3=rprt M
 1 4=D  2 4=K  3 4=R  4 4=Y  5 4=3  6 4=  7 4=rprt T
 1 5=E  2 5=L  3 5=S  4 5=Z  5 5=4  6 5=  7 5=CQ
 1 6=F  2 6=M  3 6=T  4 6=  5 6=5  6 6=/  7 6=final K
 1 7=G  2 7=N  3 7=U  4 7=  5 7=6  6 7=?  7 7="SK"

This is all only experimental at present and the codes and mode may change but it is an interesting idea. M0BMU has already been copied stateside on 136 with this mode.

Thanks to all those who have got this off the ground so quickly.. ON7YD, G4JNT and DF6NM.