433 MHz UHF lost model radio beacon

Here's a simple 433.92 MHz short range radio beacon that may be handy for locating downed R/C planes, lost ballons, model rockets - or perhaps hidden transmitter "fox hunts"!  433.92 MHz is internationally a free band slot, and although only low power transmitters (10-25 mW) are legal, UHF signal punch thru' light vegetation etc is superior to 2.4 GHz microwaves.  

It's based around a cheap (~US$5-10) low power (a few mW)  Keymark/Spirit-On TXC1 data transmitter, fooled into transmitting audio tones generated by a cheap PICAXE-08M microcontroller. Ranges are up to a km line of sight, dropping to  100-200 metres thru' light vegetation and wooden buildings etc.  Compared with flashing lights & beepers, the beauty of a wireless locator relates to all hours convenience & simple direction finding even thru' light vegetation etc.  A cheap "sniffer" receiver ( based around a companion RXB1 Keymark receiver module) is shown at => http://www.picaxe.orcon.net.nz/433RX.htm

NOTE- keep this simple locator beacon approach in perspective! Do not expect it to locate the likes of your $$$$ FPV (First Person View) model plane downed miles from anywhere in deep woods.  For serious locator use, more powerful  transmitters & GPS encoding should be considered. These of course can be costly, have higher battery drain and may be tedious to configure .

UPDATE - early 2012:  Chinese firm Dorji have recently released some cheap (~ US$10 a matched TX/RX pair) ASK 433 MHz data modules have may also suit this beacon need. Their transmitter is particularly appealing, as it's power is boosted to a (legal) 25 mW, giving ranges  some 4-5 times greater than the KeyMark/SpiritOn equivalent ! See =>http://www.picaxe.orconhosting.net.nz/dorjiask.htm

Step 1

Classic Keymark ASK data modules are only modest performers, but they're cheap (~ US$5-10), very popular, widely available,reliable and easy to use.  More sophisticated powerful and sensitive 433 MHz transceiver modules are now being marketed by the likes of Appcon & HopeRF,but  these new offerings can be a real pain to configure!

Comments

[TedRobotBuilder]

Very cool idea. I saw these modules on Sparkfun the other day and thought they might be used for robot navigation (distance and bearing).

[manuka]

Happy to help ! Perhaps initially check my crusty old PICAXE resource site http://www.picaxe.orcon.net.nz for ideas. However the best PICAXE resource is at the makers http://www.picaxe.com  This Hellscreiber circuitry is really an engine - it can modulate almost any transmitter. I simply used the 433 MHz one for simplicity. Stan

[marc_is_curious]

thanks, again -
great resource & helpful script which allows to create different types of rf sending/receiving devices !

[manuka]

Marc: Where are you ? Have you referred to the SMT resource page => http://www.picaxe.orconhosting.net.nz/smthell.htmThe PICAXE-08M SMT code is here =>http://www.picaxe.orconhosting.net.nz/VKZLHELL.BAS

[marc_is_curious]

please accept my apologies for my late reply-
and, much more important:

thanks so much for posting the links!
will have a look at it asap - (late over here - 4.20 AM)

(did some research meanwhile and found another really helpful example on instructables
http://www.instructables.com/id/Wireless-temperature-sensor/ )

besides:
orcon has plenty of sources too, thanks a lot, again!

Best Regards
Marc

[marc_is_curious]

am a total newbee to picaxe (not to mention microcontroller coding)
hence commands such as HIGH, LOW, SLEEP and GOTO are not easy enough to master for me yet :

- would you mind to hint me towards how to code this
or
probably post a link for similar examples ?

apologies for being that helpless - i did my googling
and did not find one example for a newbee-easy-to-understand-
picaxe rf transmitter-receiver example
including code and schematics example yet
(not to mention a "breadboarded" or "circuited" image coming with it)
and was happy to find your instructable!

however: thanks for posting all this!

[marc_is_curious]

i would love to build this -
may i ask which code you are refering to ?

http://www.picaxe.orconhosting.net.nz/
- Multi-tone (SMT) Hellschreiber

which -amongst other links- links to ...
http://www.members.westnet.com.au/page3/picaxe-08m_mimi_28mhz_beacon.htm

which links to ...
http://www.members.westnet.com.au/page3/PICAXE-08M_Mini_28Mhz_Beacon_Code_Ver2.txt

[sdtacoma]

This looks awesome. I am interested in building one to track down a balloon. Do you have a list of parts used? I see them here-and-there in the Instructable but a list would be very helpful.

[looking4ideas]

The range of this project will be too small to locate a Balloon that may have landed miles and miles away from you.

[manuka]

looking4ideas: Splutter- I DID say limited range at the intro ! A simple RDF antenna (such as a "cotanga" Yagi) can give a few hundred metres range thru' light vegetation & a good 500m- 1km line of sight (LOS). Elevating yourself on a low hill, rooftop or even a ladder can allow scanning over a field etc for beaming insights. Many lost models & balloons etc are of course snagged in the tree tops, and may otherwise be invisibly almost above you when searching at ground level!

[sdtacoma]

Yes, the range is not good enough to find it from miles away. I am just hoping that this can narrow down it's direction/location when close to it. Plus it is small and light.

[manuka]

go_junior8: Bravo on the keen observation! The cap. can go to either pin of the PICAXE, but I'd moved it to it's own output ( "Pin2") on this Instructable for flexibility. This way the LED can be controlled on it's own. On the older layout I had it in parallel with the LED of course at "Pin1". The PICAXE will indeed have to be programmed with something first. For insights see resources such as http://www.picaxe.orcon.net.nz 

[manuka]

Good point! I'll add a parts list to suit. The key goodie however is the Keymark/SpiritOn 433 MHz TX module.