Ports: Fsk - microHAM micro KEYER 2R Manual

Note: "Disable router queries" disables Router polling only when port has been opened by an
application. When the virtual port is closed, Router always polls the radio to support the automatic
switching functions of MK2R. If you want to completely disable all polls, select "none" instead of the
radio model in the Radio box.
Warning: Always select "none" when configuring microHAM Band Decoder through MK2R.
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 from the computer serial port (or an external modem). This signal is 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 generated by the computer sound card (or external modem) used in the
transceiver modulation circuits for operating digital modes as 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 to the FSK channel 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.
microHAM © 2006 All rights reserved
FSK PORT
31
Edited by Geoff Anderson, G3NPA