But Dave, the soundcard is doing that already!

Most Ham RTTY is in Baudot (Paul, take note), I've never seen any ASCII on
air although it was experimented with when machines became available. The
actual code is called Murray Code. Baudot is a bit of a misnomer as it
really refers to timing.

MMTTY will do all the timing/decoding of the characters in RTTY, the sound
card will perform the audio processing. For a good old fashioned TU, even
one in a PIC, you will need some good audio filtering and processing in
order to clean up the tones. My old unit was called an ST6 and might appear
on Google. It consisted of some audio filtering, then two tuned filters
using toroids (88mH) then a slicer and a level shifter.

This unit could only handle two frequencies 2125 and 2295Hz for a 170Hz
shift signal. Since RTTY is also being sent on the ham bands with 200Hz
shift, you will need to account for this. Since then, new chips became
available from Exar to decode the audio tones, based on PLL's, but it must
be said, the audio performance was never quite as good under noisy
conditions. The DSP in new soundcards now run rings around this old process.

To assist you in your quest I suggest you read some of the notes with MMTTY
as he refers to the signal processing in them. Also, there was a Greenkeys
website around a couple of years ago with a lot of information about RTTY
signalling which might help.

Nana (aka Brad VK2QQ)

wrote in message
ps.com...
I'm still open to what type of RTTY to use... and as far as
transmitting, I'm not using available software or a UART/USART chip.
My goal is to program a PIC so that it can control a FSK circuit and
transmit to my PC, which is receiving with MMTTY or something similar.
Thanks for the info all!
Dave

nana wrote:
But Dave, the soundcard is doing that already!

Yes, indeed it is. But I wouldn't be looking to transmit via a PIC if
I could take a PC along. I'm looking for a PIC-based solution in order
to make it flight-weight.

Dave

What will you display on?

wrote in message
oups.com...

nana wrote:
But Dave, the soundcard is doing that already!

Yes, indeed it is. But I wouldn't be looking to transmit via a PIC if
I could take a PC along. I'm looking for a PIC-based solution in order
to make it flight-weight.

Dave

My PC will be the receive station.

nana wrote:
What will you display on?

wrote in message
oups.com...

nana wrote:
But Dave, the soundcard is doing that already!

Yes, indeed it is. But I wouldn't be looking to transmit via a PIC
if
I could take a PC along. I'm looking for a PIC-based solution in
order
to make it flight-weight.

Dave

But, if you are displaying it on a PC, won't the sound card be inside it?


wrote in message
oups.com...
My PC will be the receive station.

nana wrote:
What will you display on?

wrote in message
oups.com...

nana wrote:
But Dave, the soundcard is doing that already!

Yes, indeed it is. But I wouldn't be looking to transmit via a PIC
if
I could take a PC along. I'm looking for a PIC-based solution in
order
to make it flight-weight.

Dave

Yes, RECEIVING with the PC. Transmitting via a PIC. The PIC will be
airborne. My PC will not.

nana wrote:
But, if you are displaying it on a PC, won't the sound card be inside
it?

Finally, Dave is beginning to give us the complete story.

Now, Are you thinking of generating audio tones using the pic in order
to transmit AFSK, audio frequency shift keying? This will basically be
filtered and sent to the microphone input of a transmitter. Or are you
going to use the pic to control a tone generator? What you use as a
transmitter has a lot to do with how complex the PIC program will be an
which PIC you will use.

Several years ago my company hired an engineer to develop a fax/modem
phone line switch using a 16 bit PIC. I don't remember the number.
Anyway, the circuit he designed and the software the programmer
developed watched for the phone ring tones and for the tones sent by
fax machines. It also generated the ring tones to ring the telephone on
the line it had selected. Just as with your project, it never had to do
all at the same time, although,I think the timer generating the tone
could continue until the PIC turned it off.

Have you looked at all the data sheets and sample programs available
for the PIC from the manufacturer? It's been a long time since I looked
there, but I think there were sme good examples of what you want to do.
Paul, KD7HB

nana wrote:
But Dave, the soundcard is doing that already!

Most Ham RTTY is in Baudot (Paul, take note), I've never seen any ASCII on
air although it was experimented with when machines became available. The
actual code is called Murray Code. Baudot is a bit of a misnomer as it
really refers to timing.

W1AW sends bulletins in 110 baud ASCII.

http://www.arrl.org/w1aw.html

--
Jim Pennino

Remove -spam-sux to reply.

W1AW sends bulletins in 110 baud ASCII.

http://www.arrl.org/w1aw.html

--
Jim Pennino

Well, they'd be about the only ones!

Nana