RTTY / FSK Configuration
Fldigi operates RTTY using AFSK and the transceiver set to USB. The
RTTY signal can be transmitted anywhere within the USB passband of the
transceiver.
You can select from various Shifts, Bauds, Bits, Parity and Stop Bits
for both AFSK and FSK keying of the transmitter. You can elect to
have fldigi automatically insert a CFLF when it reaches character 72 on
a line. You can also have it insert a CR-CR-LF sequence instead
of the standard CR-LF sequence. This is very useful if you are
communicating with someone using a hardware TTY printer. The
extra carriage return will give the physical device time to move to the
left margin before new characters arrive.
The RTTY decoder maintains an internal AFC system for tracking the
desired signal. Depending on operating conditions you may need to
adjust the action of the AFC loop. Select from the Slow, Normal
or Fast AFC loop. You can also disable AFC with the AFC button on
the main panel.
The Digiscope display can be defaulted to the X-scope or the Signal
scope. The X-scope is similar to older hardware scopes that show
the Mark/Space channel signals as quadrature signals.
The
DSP bandpass filter preceeds the decoder. You can adjust the
bandwidth with the Receive filter bandwidth control. The
bandwidth is reflected on the waterfall tracking indicator.
PseudoFSK selection generates an additional audio signal on the right
channel. This signal is a burst tone at the FSK keying rate.
You can full wave rectify and filter the signal so that it can be
used as the FSK keyline signal to a rig that supports FSK transmissions. See Pseudo FSK for additional information and a suitable keying circuit.