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Old Apr 26, 2012, 12:27 PM
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Has anyone here done FSK telementry?

Just want to know if there is any code out there for it, I know there are some libraries but I am not really sure what approach I should take.
My idea is that I will just send GPS data as one transmission every gps update, over the audio channel, then have an arduino at the ground station to decode and send it over serial.Which obviously can then be used with some gui to map.
Doesn't sound that unreasonable and should be good for tracking on the cheap.
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Old Apr 26, 2012, 01:50 PM
Stuart
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There is a differance between FSK modulation and sending data over the audio channel.

Which is it you are trying to do ?
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Old Apr 26, 2012, 02:18 PM
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Quote:
Originally Posted by srnet View Post
There is a differance between FSK modulation and sending data over the audio channel.

Which is it you are trying to do ?
I had a look at Diydrones and it said they used FSK so I assume it is most used.
I am not sure it matters as it goes like this
Analog audio+Video signal--->RF modulation---->Receiver demodulation-->Analog audio+Video signal.
I don't see why I have to go with FSK, surely PWM would be fine? I will just go with the simplest.
I looked up about Earthbridge, I will then just take the NMEA data from the receiver and plug it into that and the job will be done.

Edit: Found out that the transmitters don't like low frequencies so FSK seems the most logical.
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Old Apr 26, 2012, 02:36 PM
The Fixer
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You can do it with a couple of Xbee's. The GPS just connects to one and the computer the other. I'm doing it this way with my diy tracker.
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Old Apr 26, 2012, 02:57 PM
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Originally Posted by Martin Y View Post
You can do it with a couple of Xbee's. The GPS just connects to one and the computer the other. I'm doing it this way with my diy tracker.
Yep you can but this costs about 8 and has a better range.
Xbee is good but quite expensive.
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Old Apr 26, 2012, 03:04 PM
Stuart
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I dont think your clear on what it is you are trying to do.

You cant take a normal conventional Video\Audio link and somehow add FSK (as in direct data) modulation to it, although you can use the audio link for the likes of RTTY, Morse etc.
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Old Apr 26, 2012, 03:05 PM
Stuart
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[QUOTE=chaosdestro0;21444009]Yep you can but this costs about 8 and has a better range.
[QUOTE]

What costs 8 ?????
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Old Apr 26, 2012, 03:18 PM
Stuart
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Originally Posted by Martin Y View Post
You can do it with a couple of Xbee's. The GPS just connects to one and the computer the other. I'm doing it this way with my diy tracker.
Out of interest, what sort of range do you get in the air ?

I have just built something along those lines, a GPS tracker that transmits location and\or distance and direction from home.

http://www.picaxeforum.co.uk/showthr...on-Calculation

I went the Morse route since you can decode slow speed morse numbers easy enough by ear and the unit has a ground range LOS of circa 20 miles. The module has a TX power capability of 100mW, which does not sound a lot, but there are similar beacons in orbit, flying at an altitude of 450miles, that can clearly be heard on terra firma.
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Old Apr 26, 2012, 03:33 PM
The Fixer
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Can you post those files? As I dont want to join yet another forum.

Quote:
Originally Posted by srnet View Post
Out of interest, what sort of range do you get in the air ?

I have just built something along those lines, a GPS tracker that transmits location and\or distance and direction from home.

http://www.picaxeforum.co.uk/showthr...on-Calculation

I went the Morse route since you can decode slow speed morse numbers easy enough by ear and the unit has a ground range LOS of circa 20 miles. The module has a TX power capability of 100mW, which does not sound a lot, but there are similar beacons in orbit, flying at an altitude of 450miles, that can clearly be heard on terra firma.
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Old Apr 26, 2012, 03:34 PM
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Quote:
Originally Posted by srnet View Post
I dont think your clear on what it is you are trying to do.

You cant take a normal conventional Video\Audio link and somehow add FSK (as in direct data) modulation to it, although you can use the audio link for the likes of RTTY, Morse etc.
I am not adding it on top, I don't use the audio channel.
I just made this up, haven't tested it yet though.
Quote:
#include <SoftModem.h>


SoftModem modem;

void setup ()
{
Serial.begin (57600);
delay (1000);
modem.begin ();
}

void loop ()
{

if (Serial.available ()) {

while (Serial.available ()) {
char c = Serial.read ();
Serial.write(c);
modem.write (c);

}
}
}
The at mega328 chips are 4 a piece, I assume you have a gps unit.
And the ground station code is just as simple.
So all you do is connect the rx to the gps unit and ground. Run this and check the serial monitor. If you want to use the modem then you should really put a filter.

I will hopefully order some arduinos this weekend and play around with it next week, see if I can get it to work fine. This is just a really dirt cheap way of telemetry.
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Old Apr 26, 2012, 03:56 PM
Stuart
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Have we missed something ?

What is the unit the other side of 'FSKIN' and 'FSKOUT' ????
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Old Apr 26, 2012, 03:58 PM
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Originally Posted by srnet View Post
Have we missed something ?

What is the unit the other side of 'FSKIN' and 'FSKOUT' ????
FSKIN will be the audio input on the transmitter and FSKOUT will be from the receiver to another arduino or even a microphone port on your computer.
Then you will have a FSK signal on your ground station, so you can either use another arduino to demodulate it and then use Earth Bridge to map it onto google earth.
50 baud RTTY transmission using the Arduino (7 min 21 sec)

That's basically what it does..
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Old Apr 26, 2012, 04:06 PM
Stuart
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Quote:
Originally Posted by Martin Y View Post
Can you post those files? As I dont want to join yet another forum.
I would rather not post the code in another location.

Its easier to make futures changes or fixes if the code is in one location, and as its a PICAXE project ........
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Old Apr 26, 2012, 04:37 PM
Stuart
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Originally Posted by chaosdestro0 View Post
That's basically what it does..
What the Video appears to describe is actually RTTY using audio tones. This is audio frequency shift keying (AFSK) which and can indeed be sent down the audio channel.

FSK is something different, look it up.

I have tried AFSK RTTY and I found the performance of the link no better (for this sort of application) than high speed Morse.

Once you have the routines working its easy to switch to slow speed Morse which can be read by ear at 4 to 5 times the distance of PC\Micro based automatic decoders.
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Old Apr 26, 2012, 05:03 PM
Quad lover.
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Quote:
Originally Posted by srnet View Post
What the Video appears to describe is actually RTTY using audio tones. This is audio frequency shift keying (AFSK) which and can indeed be sent down the audio channel.

FSK is something different, look it up.

I have tried AFSK RTTY and I found the performance of the link no better (for this sort of application) than high speed Morse.

Once you have the routines working its easy to switch to slow speed Morse which can be read by ear at 4 to 5 times the distance of PC\Micro based automatic decoders.
Thanks for your feedback, I will investigate that as well.
I didn't realize there was a difference, I guess I will go for morse code due to your investigations.
What kind of frequencies are you getting?
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