Fsk & 2 - microHAM MK2R Manual

The FSK channel is used by the application program to send the FSK keying signal. FSK is used primarily for
RTTY. It is very important to understand the difference between FSK and AFSK.
FSK is a digital (On/Off) signal used in the transceiver to generate a frequency shift. FSK must be supported by
the transceiver (this mode is commonly labeled RTTY or FSK).
AFSK is an analog (audio) signal used to modulate the transceiver for digital modes like RTTY, PSK31, AMTOR
etc. Computer sound card generated AFSK or PSK does not require special transceiver support and can be
used in the LSB, USB or FM mode of the transceiver. Some radios have dedicated modes for AFSK (generally
labeled PKT, DATA, LSB-D or USB-D) with special features.
It is very important to properly adjust the audio drive level of an AFSK system so as to not overdrive the first
transmit audio amplifier stage in the transceiver and produce a wide, distorted signal, full of intermodulation
products. It is important to appreciate that distortion generated at this point due to overdrive CANNOT be reduced
or eliminated by the reduction of the microphone gain control – it is the signal level that must be adjusted to be
about the same as would be expected from a microphone. The microphone gain control then becomes a form of
transmit power control.
An initial indication of proper audio drive level can be seen on the ALC meter of the radio. Provided that there is
NO audio processing in circuit and that the microphone gain control is in its normal operating position, then, if the
ALC does not show or just starts to indicate during transmission, the signal is likely to be clean. It is also
important is to turn off the microphone compressor, ANY transmit audio equalizer, AND transmit DSP when
AFSK is used. DO NOT use any form of digital modulation (sometimes called "Transmit DSP") with AFSK or
PSK. Some transceivers bypass these circuits automatically when signal is routed to the rear audio jack instead
of the microphone jack, but some do not (for example, the TS-850).
If your transceiver supports FSK, use FSK for RTTY whenever possible. It's the only sure way to get a
clean RTTY signal no matter the microphone gain or compressor (processor) settings on your radio.
When a COM port is assigned in Router but not in the application program (or the application is not running),
Router will indicate the channel is closed.
When an application opens the COM port, Router
will indicate the channel is open and display baud
rate, number of data bits, parity and number of stop
bits in use. For example, 45 5N1.5 means: 45
Baud, 5 data bits, no parity, 1.5 stop bits.
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The 2 FSK port is useful when operating split with radios that have two receivers (e.g., FT-1000, FT-2000, FT-
9000, K3, Orion or IC-7800). The second instance of the RTTY program should specify "right channel" for its
audio source and should be configured to use the 2
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The 2 FSK port can also be used for a second RTTY program with a different decoding algorithm to provide
diversity decoding and transmit from either program.
TIP: If you see a baud rate other than 45.5 baud (e.g., 4800 or 9600), the application is NOT configured
correctly for FSK RTTY operation.
PTT: The virtual port used for FSK can also support PTT (required by MMTTY). When you use MMTTY, select
the PTT box and RTS will used for PTT. Do not use the FSK port for any other function.
Invert: Some transceivers lack the ability to set the sense of the FSK input. If you cannot set the proper sense,
check the invert box. This is normally necessary only with the Ten-Tec Omni V, Omni VI and Kenwood TS-940.
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FSK & 2 FSK PORTS
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FSK port for its FSK output.
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Edited by Geoff Anderson, G3NPA