Sholto - I was referring to my design as not being designed for on/off switched, not the Hell mode itself which of course IS.
Its really not reasonable to expect beginners to ressurrect old dead software and dead operating systems to get something up and running. Configuring MMTTY to toggle the TXD line on a proper serial port is not too difficult. I doubt if a threshold switch could be made fast enough without more hardware and design thought applied to it than the simple Tx itself. However, as most soundcards go down to a few low tens of Hz in audio bandwidth, I've more than once thought of using it to directly output a Manchester coded type of waveform that could be squared up and turned back into a proper digital signal with probaly no more than a flip-flop. It might then even be fast enough for RTTY. Referring to other comments earlier, why do so few datamode programmes provide I/Q stereo outputs? Quadrature upconversion is probably the easiest low-end option for all datamodes, especially if it is done at baseband where the unwanted image lies on top of itself, causing n QRM. Image rejection can be as bad as -20dBc before any problems occur going this route. Even with an audio carrier, it is not difficult to -40dBc rejection without too much trimming, and at QRP levels that's not going to be much of an issue. I reiterate, its only a few extra lines of code :-) chans = 2 X = AMPL * SIN(~~~ output left Y = AMPL * COS(~~~ output right or output I output Q Andy www.g4jnt.com --- In digitalradio@yahoogroups.com, "sholtofish" <sho...@...> wrote: > > Andy, > > You said: > > > FeldHell or whatever isn't an option. Its not on/off keyed - quite > > intentionally - and FSK Hell needs more setting up than RTTY. > > In it's simplest form Feld Hellschreiber IS on/off keyed! That's the way > Rudolf Hell did it back in 1929. > > I seem to remember a dos program from years ago that simply toggled either a > serial port bit (or parallel port bit) and you could use that to drive a > simple transmitter. > > Nowadays as most people don't have either serial or parallel ports on their > computer, the sound card is the most accessible port and by constructing a > simple threshold detector switch you could achieve the same result. > > 73 > > Sholto > K7TMG > > > --- In digitalradio@yahoogroups.com, "IMR" <ac.talbot@> wrote: > > > > > > >In your MMTTY folder (the one that contains the file mmtty.exe), > > >is the file extfsk.dll present? > > > > > > > > No. > > n fact that file is nowhere to be found on the machine at all :-( > > So guess I need to go back to your download page and find it. > > > > Its all getting too complicated - the design was a request for a simple Tx > > for beginners that wasn't yet another CW QRP transmitter - and I was hoping > > RTTY would be as dead-simple to get going as it used to be back in the days > > of yore. Clearly not. > > > > It might even be easier to wrirte my own simple RTTY Tx terminal in VB6. > > Waggling the TXD line using the "MSComm1.Break = True/False" function will > > do the job if timing can be assured. > > > > And to the others who made comments - > > Setting the shift is part of the self education process - I suggested they > > use Spectran or SpecLab on thre output on an SSB Rx to set up the shift at > > test. Only a case of tweaking a preset R > > > > FeldHell or whatever isn't an option. Its not on/off keyed - quite > > intentionally - and FSK Hell needs more setting up than RTTY. > > > > Next time a request like that arrives, I'll be boring and just give them > > an I/Q upconverter + linear amp. > > > > Which reminds me - where is all that datmode software that delivers I/Q > > stereo outputs. Its only another line or two of code surely. > > > > Andy > > www.g4jnt.com > > >
