[Paweł Spychalski] wrote in to tell us about some experiments he’s been doing, using cheap 433 MHz HC-12 radio units as a telemetry radio for his quadcopter.
In this blog post, he goes over the simple AT command set, and some of the limitations of the HC-12 part. Then he takes it out for a spin on his quadcopter, and finds out that his setup is good for 450 meters in an open field. Finally, he ties the radio into his quad’s telemetry system and tethers the other end to his cellphone through a Bluetooth unit for a sweet end-to-end system that only set him back around $20 and works as far out as 700 meters.
The secrets to [Paweł]’s success seem to be some hand-made antennas and keeping the baud rate down to a reasonable 9600 baud. We wonder if there’s room (or reason?) for improvement using a directional antenna on the ground. What say you, Hackaday Antenna Jockeys?
Also check out this very similar build where an ESP8266 replaces the Bluetooth module. And stashes it all inside a nice wooden box! Nice work all around.
11 thoughts on “Easy DIY Telemetry Goes The Distance”
A pair of 500mW 3DR telemetry radios (clones) can be had for only $30 and will give you a 2km range at a 64kbps rate with stock antennas (tested on tricopters).
Yes, good antennas and antenna tracking systems (can be made for about $40 in electronics) is always considered superior to transmit power and can give you hundreds of kilometres with those same radios.
Or if you have a video transmitter use the audio channel, it has plenty room for 9600 with the added bonus of having it recorded on your video and not having to listen to prop- and wind noise.
Please can you give more details on this.
I split the electronics from this into a sender and reciever with arduino pro mini, works a charm over audiochannel on vtx.
get even more by learning antenna theory. a turnstile antenna on the bottom of the quadcopter would increase range even more and eliminate the PITA phasing as it will be a circular polarization. have a nice turnstile on the ground as well. add a ground plane reflector to the ground station and gain an additional 3db of signal gain.
Even more range can be had by increasing ground transmit power and adding a Receive preamp.
any ideas where I would get info on the phasing for turnstile antennas at this frequency?
also for 900Mhz and 2.4Ghz
Is it anything like using a short piece of coax like we do for 137Mhz??
Any good sources you can recommend on getting into this stuff? Preferably with all the complex-domain math derived out.
Nice I think I have these part lying around. Indoors they didn’t perform to well for me unless I used lower baud rates or better error correction.
I’ve definately noticed improved distance with lower baud rates on cheap RF boards. The 315/433 KLP boards got noticeably better distance by going down to 1200baud. If the telemetry doesn’t require the baud rate, keep going down.
These HC-12 modules are certainly the best bang for buck going ( typically US$10 a pair with free global p&p), although realistic ranges at even low baud rates ( 1200bps) will only be approx. 100 metres thru’ typical urban clutter. Their included “spring” antenna is no great performer – simply replace with a ~165mm length of wire etc. AT command config. works OK but is tedious. A great Win graphical config. utility written by a fellow Kiwi is far easier- free download => http://www.thebackshed.com/forum/forum_posts.asp?TID=8246&PN=1
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