[aprssig] PIC and Modem experienting

[Jason Winningham]

On Apr 24, 2007, at 7:30 PM, Andrew Rich wrote:

> Gudday
>
> I have been playing with a PIC chip and a GPS and a 433 MHz pair of  
> radio modules.
>
> The radio modules use ASK or OOK. I have had limited success and  
> the link is immune to corruption.
>
> I am thinking of trying MX614 and the PIC for telemetry.

The ISM modules I've seen have digital inputs and take care of the  
modulation themselves - the MX614 doesn't have anything to do.

I have an audio transmitter (from Abacom, IIRC) that has a simple  
audio input.  I tied an opentracker to it and flew it on a balloon.   
SAW oscillator drifted terribly in the cold, but it otherwise worked OK.

>  Anyone playing with PIC's for telem ?

I tried an AVR one time and abandoned the PIC - the development  
support is way better for the AVR, and free to boot.

> Looking for a source of MX614 down under as well.

Can't help you there.

The XR2206/XR2211 pair take quite a few more passive components to  
implement, but are cheaper, may be easier to find, and can work on  
different audio tones so you can use the same circuit with different  
passives to implement other AFSK systems like 300 baud packet, NOAA  
SAME transmissions, etc.  Check out the T2 for an XR2211 receiver  
design.  I suspect I'd use PWM on the microcontroller rather than  
mess with the 2206 if I tried to implement the transmit side.

-Jason
kg4wsv