Arduino based telemetry system - RF with Arduino

Hi,

I am part of a project looking into creating a telemetry system using an Arduino. I would like to transmit data gathered by the Arduino on the 70cm band back to our ground station (yes I do have my ham radio license... however this is my first project trying to build my own Tx system).

The data to be transmitted would come from a sensor network and GPS, also connected to the same Arduino. I would like the data transfer rate to be as fast as the Arduino is capable of. My current thoughts are to tackle this using PWM on the Arduino Mega to act as my frequency modulation, using a digital-to-analog converter to change the output of the Arduino to AC, boosting this output up to the level I need with an op-amp, and then building my own tuned circuit to achieve the correct impedance with the antenna I have.

As far as using RF systems for Arduino that already exist, I have read about the XBEE products for RF, however we're looking for a system that has more range than even the 900Hz chip they have, which as far as I've read is the lowest frequency Tx available from them. If there are any products available that can integrate with Arduino easily and can use the 70cm band, I would love to hear about them!

Do you think my approach is feasible? If anyone has experience trying to create this type of system, what difficulties did you have? If it helps, this telemetry system is intended for high powered rocketry applications.

Please let me know if more clarification is needed. Thanks.
E

In most countries you will also have to identify your call sign using a normal protocol, like CW.

Paul

LoRa radios can be used legally without a license (with restrictions), are cheap, easy to use, and have clear line of sight ranges of over 700 km at 25 mW TX power.

I would like the data transfer rate to be as fast as the Arduino is capable of.

The radio is almost always the limiting factor.

You can also use 900MHz/433MHz, 500mW, SiK UART radios.

Also, if you do decide to use UART radios, I highly suggest using the fast, easy, and efficient data transfer library SerialTransfer.h. It's installable through the Arduino IDE's Libraries Manager and comes with many examples.

Here are the library's features:

This library:

  • can be downloaded via the Arduino IDE's Libraries Manager (search "SerialTransfer.h")
  • works with "software-serial" libraries
  • is non blocking
  • uses packet delimiters
  • uses consistent overhead byte stuffing
  • uses CRC-8 (Polynomial 0x9B with lookup table)
  • allows the use of dynamically sized packets (packets can have payload lengths anywhere from 1 to 255 bytes)
  • can transfer bytes, ints, floats, and even structs!!

Paul_KD7HB:
In most countries you will also have to identify your call sign using a normal protocol, like CW.

Paul

I think it runs deeper than that… if I’m not mistaken, the message content is regulated also, and telemetry is specifically forbidden There is some grey area around this due to remote repeater control, automated CW beacons, and APRS, but I believe non-amateur radio related telemetry transmissions are not allowed at all on the ham bands in North America.

APRS tested the limits, and I think would have been prohibited, had the FCC the motivation and resources to fight it.

You might google "packet radio".

zoomkat:
You might google "packet radio".

Me?

aarg:
Me?

Are you the one looking to make an "Arduino based telemetry system"? :wink:

zoomkat:
Are you the one looking to make an "Arduino based telemetry system"? :wink:

I don't believe it is legal to use packet radio for telemetry, either. From what I can remember of the USA regulations, there isn't any ham band where it is.

aarg:
I think it runs deeper than that... if I'm not mistaken, the message content is regulated also, and telemetry is specifically forbidden There is some grey area around this due to remote repeater control, automated CW beacons, and APRS, but I believe non-amateur radio related telemetry transmissions are not allowed at all on the ham bands in North America.

In the UK at least it is deeper than that.

Here the Amateur license does not permit use from airborne devices and in addition there is an overiding consideration that 'messages' must be to and between licensed amateurs, with a few exceptions. Broadcasting telemetry for your own purposes would fall outside of whats permitted.