Title: MSP430 CW TX
Post by: toxic239 on May 22, 2012, 03:21:32 am
Post by: toxic239 on May 22, 2012, 03:21:32 am
Hi Guys,
For an upcoming low altitude party balloon flight :D we had to put together a simple Morse transmitter. The idea is to use the cheapest MSP430 (USD 1.27 on digikey) to measure temperature and send continuously a simple message "CALLSIGN T<TEMP> 73". The generator and RF power amplifier is built using 74AC00 and a quartz for 20m (14.089 MHz) with output filtered via a Pi filter.
Board and software attached. Happy CWing!
Toxic239
For an upcoming low altitude party balloon flight :D we had to put together a simple Morse transmitter. The idea is to use the cheapest MSP430 (USD 1.27 on digikey) to measure temperature and send continuously a simple message "CALLSIGN T<TEMP> 73". The generator and RF power amplifier is built using 74AC00 and a quartz for 20m (14.089 MHz) with output filtered via a Pi filter.
Board and software attached. Happy CWing!
Toxic239
Title: Re: MSP430 CW TX
Post by: arakis on May 22, 2012, 10:37:42 am
Post by: arakis on May 22, 2012, 10:37:42 am
Great project,
would it have been possible to use the crystall to run the clock of the uC, and use a timer for carrier frequency, and do internal soft controll for signal generation?
would it have been possible to use the crystall to run the clock of the uC, and use a timer for carrier frequency, and do internal soft controll for signal generation?
Title: Re: MSP430 CW TX
Post by: toxic239 on May 22, 2012, 02:02:58 pm
Post by: toxic239 on May 22, 2012, 02:02:58 pm
Hi, the idea was to use low power mode hence we are using built in VLO. The timings for CW are not that critical to warrant the use of high frequency oscilator.
Title: Re: MSP430 CW TX
Post by: ginpb on May 22, 2012, 10:48:30 pm
Post by: ginpb on May 22, 2012, 10:48:30 pm
Hi, really nice.
What is the range?, what do you use to receive, a radio, SDR?. Why morse?.
Thanks for sharing.
What is the range?, what do you use to receive, a radio, SDR?. Why morse?.
Thanks for sharing.
Title: Re: MSP430 CW TX
Post by: robots on May 22, 2012, 11:09:32 pm
Post by: robots on May 22, 2012, 11:09:32 pm
Morse because it is just carrier.
You should also be aware that this transmitter will probably require proper license to operate ;)
You should also be aware that this transmitter will probably require proper license to operate ;)
Title: Re: MSP430 CW TX
Post by: toxic239 on May 23, 2012, 03:01:42 am
Post by: toxic239 on May 23, 2012, 03:01:42 am
Correct - you need to have an amateur radio license in order to operate such unit legally ;)
Transmission via Morse code is the easiest to implement in hardware and the idea here is to make this unit cheap. Lot of guys are using complex set-ups of camera + computer + GPS and a meteo baloon, but we would like to use party balloons :D !
The reason why to transmit temperature is that MSP430 already has a temperature sensor and combining with weak signal transmission procedure called QRSS (very very very slow Morse) we should be able to be heard in quite a few places and also identify how high are our balloons. I am counting for at least 5000+ km range with proper antenna (read 5m of straight wire: 1/4 of 20m wave length at 14MHz).
For the reception we will post a simple direct conversion receiver (no crazy inductors there!) once the project is finished.
Best Regards,
Toxic239
Transmission via Morse code is the easiest to implement in hardware and the idea here is to make this unit cheap. Lot of guys are using complex set-ups of camera + computer + GPS and a meteo baloon, but we would like to use party balloons :D !
The reason why to transmit temperature is that MSP430 already has a temperature sensor and combining with weak signal transmission procedure called QRSS (very very very slow Morse) we should be able to be heard in quite a few places and also identify how high are our balloons. I am counting for at least 5000+ km range with proper antenna (read 5m of straight wire: 1/4 of 20m wave length at 14MHz).
For the reception we will post a simple direct conversion receiver (no crazy inductors there!) once the project is finished.
Best Regards,
Toxic239
Title: Re: MSP430 CW TX
Post by: ginpb on May 23, 2012, 10:09:06 am
Post by: ginpb on May 23, 2012, 10:09:06 am
thanks for your answer toxic239, but you could use a manchester encoding, you just need an XOR between the clock and the signal.
Title: Re: MSP430 CW TX
Post by: toxic239 on May 23, 2012, 02:57:20 pm
Post by: toxic239 on May 23, 2012, 02:57:20 pm
As far as I know (please correct me) direct transmission of Manchester coded data will only work through digital channel when using simple XOR gate. For analog channel we still need to modulate the carrier frequency somehow.
Here's a simple link how this is done for BPSK (PSK31), schematic courtesy Clint Turner. We will see how easy it will be to implement such solution in MSP430 after our party balloon flight :D
Here's a simple link how this is done for BPSK (PSK31), schematic courtesy Clint Turner. We will see how easy it will be to implement such solution in MSP430 after our party balloon flight :D
Title: Re: MSP430 CW TX
Post by: ginpb on May 23, 2012, 03:57:30 pm
Post by: ginpb on May 23, 2012, 03:57:30 pm
Yes you have absolutely right, I was thinking instead of put inside the nand port a series of impulses to generate a morse code you should put a manchester encoded string of bit. Manchester will give you a simple error control.
Title: Re: MSP430 CW TX
Post by: jbeale on May 23, 2012, 07:05:23 pm
Post by: jbeale on May 23, 2012, 07:05:23 pm
[quote author="toxic239"]I am counting for at least 5000+ km range with proper antenna (read 5m of straight wire: 1/4 of 20m wave length at 14MHz).[/quote]
Circuit certainly looks nice and simple, and compact! I've never done any balloon stuff, but does a 1/4 wave antenna really work with no ground plane reference? For a balloon transmitter I would assume a dipole or J-pole type antenna would be better, at least in theory.
cheers,
John
N8JUF
Circuit certainly looks nice and simple, and compact! I've never done any balloon stuff, but does a 1/4 wave antenna really work with no ground plane reference? For a balloon transmitter I would assume a dipole or J-pole type antenna would be better, at least in theory.
cheers,
John
N8JUF
Title: Re: MSP430 CW TX
Post by: toxic239 on May 23, 2012, 07:27:45 pm
Post by: toxic239 on May 23, 2012, 07:27:45 pm
I stand corrected sir! We discussed 1/4 wave antenna internally and I've missed the fact that 1/4 wave arm will be attached to GND of the board as well effectively forming a dipole. So:
Balloon <- 1/4L -> TX <- 1/4L ->
I am really excited to try the QRSS on balloon - I'll try to organise RX by my friends in Europe to test the propagation over Atlantic as well.
73!
Balloon <- 1/4L -> TX <- 1/4L ->
I am really excited to try the QRSS on balloon - I'll try to organise RX by my friends in Europe to test the propagation over Atlantic as well.
73!
Title: Re: MSP430 CW TX
Post by: robots on May 23, 2012, 11:37:43 pm
Post by: robots on May 23, 2012, 11:37:43 pm
when are you planing to send the baloon ? :) I might listen as well!
Title: Re: MSP430 CW TX
Post by: toxic239 on May 24, 2012, 03:07:02 am
Post by: toxic239 on May 24, 2012, 03:07:02 am
If it is not raining this weekend we will perform a static test on Saturday. Date 26th May 2012, Time: 2200 GMT, duration: 8h Callsign: AB1PG, Frequency: 14.089MHz (or thereabouts).
The TX power is rather low probably 10-15mW, so please listen carefully :D
Toxic239
The TX power is rather low probably 10-15mW, so please listen carefully :D
Toxic239