I've just read the original post and another thing to consider might be to try Feld Hell instead of RTTY. You wouldn't need to worry about any frequency shift that way, just use a simple transistor switch arranged to key the osc/tx from the audio pulses from the sound card. It would be completely non-linear of course but at the 1W level I don't think much of a problem but if needed you could design a filter to round off the edges a little...
Feld Hell is also a lot more sensitive than RTTY and you might actually have some success at the 1W level... 73 Sholto K7TMG --- In digitalradio@yahoogroups.com, "IMR" <ac.tal...@...> wrote: > > OK Tnx... > > found the COM port output facility and got it working on a Desktop with a > proper COM1. But when I tried a USB COM port - as suspected it wouldn't work > directly. On trying the EXTFSK option, it just comes back with a message > that says "Can't Configure EXTFSK" > Downloaded the latest MMTTY version 1.66G, just to make sure. > > What I'm not sure about, if EXTFSK is set as the data output option, how does > the software know which USB Comport is to be used for its output of the data > - if that makes sense :-) > > One FTDI USB COM port appears as COM 2 on this machine, another one as COM5 > and a third one as COM 15. (I do have several more as well, all made from > FT232 chips. Use the interface for everything) So how can it identify > which of these is the one to use for EXTFSK ?? > > Andy > www.g4jnt.com (author of the 'Data' and 'Design Notes' Columns in 'RadCom') > > > > > > >>>MMTTY provides this "FSK signal" via the TxD pin of the serial port > > specified in the "PTT & FSK" panel on the "Setup MMTTY" window's "TX" tab. > > Since using this signal requires a serial port capable of 45 baud operation, > > which some USB-to-serial-port-adaptors can't do, you can set the "PTT & FSK" > > panel's port selector to EXTFSK, which displays a window that lets you > > configure the generation of an FSK signal on a serial port's RTS or DTR > > pins. In this latter configuration, the timing of the FSK signal is > > software-generated, and thus less accurate than that generated by a 45 baud > > serial port. > > > > >>>Digital mode applications that use MMTTY as their "RTTY Engine" -- > > WinWarbler, HamScope, etc. -- thus offer this capability. > > > > > > While I realise there may be little call for such a one-wire drive now > > > > >>>Not true! Modern transceivers provide RX filtering for RTTY that is only > > availalble when the transceiver is operated in RTTY mode, thus requiring the > > "FSK signal" when transmitting. Icom's ic-7200, ic-7600, ic-7700, and > > ic-7800 all provide a very nice twin-peak filter that is only available in > > RTTY mode. > > > > 73, > > > > Dave, AA6YQ > > >
