Balloon telemetry data using radio teletype or RTTY (Baudot)

[Mike, K8LH]

Which PIC are you using John? At the risk of "going over your head", have you considered losing the XR2206 chip and generating the 2125 and 2295 Hz sine wave AF directly from the PIC (using DDS-PWM or DDS-R2R)?

Vy 73, Mike, K8LH

[johnmaetta]

Hi Mike,

It doesn't take too high of a step to "go over my head". Anyway, I am using the 16F648A and I am not sure about DDS and PWM, but I did see that some people generate sine waves with PICs. I recall seeing a PIC schematic with four resistors bridging four PIC output pins. Then I believe each pin is pulsed in sequence with varying amplitude while being swept over time. Is that the premise?

I want to learn...

73

John
N6VMO

[Dave]

johnmaetta, Why not just use a 10F222 to generate the frequency's with a fiilter? That saves a lot of parts and board space. A couple of years ago I used one to generate a 125khz carrier to send temperature and depth data to the surface from a device towed by a boat to emulate a cannon ball for Salmon fishing.

Dave Purola,
N8NTA

[johnmaetta]

Thank you to all who made suggestions and provided me help. Here is the prototype PIC RTTY Telemetry project:

http://www.n6vmo.com/PIC/SARCHAB7.zip