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Old Jan 20, 2014, 01:07 PM
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OLRB: Open Long Range Beacon -low cost tracker

by long range i mean over 25 miles and by low cost i mean less than a dollar in parts. this was inspired by my great success receiving signals at over 2000km distance from srnets low power ham satellite beacon(http://www.rcgroups.com/forums/showthread.php?t=2040936). it uses similar power and uhf frequencies so the potential is amazing. when i mentioned this in my 1gram gps thread several people asked for diy info so here we are.

basically it uses one of those cheap 50 cent ebay ook transmitter modules converted to fm and 50 cent tiny13 mcu programmed to generate the beacon signal. the rx that comes with the module is very short range but a low cost fm walkie talkie (also ebay) can provide los range of many miles. converting the tx to fm takes only a minute and a few pennies in parts (2 caps, 1 resistor). below is a photo showing one of the units with piano wire antenna. also attached is a google screenshot showing distance achieved using that same module. but in this case with yagi arrays (also easy to build for pennies). other photos included show the walke talkie and yagi. sample sound file, schematic, and arduino demo source code for the t13 too.

if you have questions or want more info or photos dont hesitate to ask.




01/28/2014

ive added a photo with gps attached using tone generation capability to send battery voltage and gps lat/lon via morse. also sound sample of that from 9 miles. its not the clearest in the world but pretty good considering, unlike the 75 mile wilderness contact, it was urban environment. plenty good enough to locate a plane as long as you or a bud know the code. its not necessary to learn all the characters but just numbers which is a lot easier. in fact by recording it with your phone or camera like i did you dont even have to know the code. just hit pause after each digit and look up in the chart. heres a snip from the morse program which might help with that. or give a head start to anybody who wants to develop their own version of the program.

Code:
.db 0b00000101,0b10000101,0b11000101,0b11100101,0b11110101,0b11111101
;     ----- '0'  .---- '1'  ..--- '2'  ...-- '3'  ....- '4'  ..... '5'
.db 0b01111101,0b00111101,0b00011101,0b00001101
;     -.... '6'  --... '7'  ---.. '8'  ----. '9'
even if you dont interpret the morse data just hearing the tones can be very useful locating a lost model with the right antenna. really the antenna doesnt even have to be that fancy. just stock rubber duckie and blocking the signal with your body like fmkit taught us will allow you to home in.



2/3/2014

heres a link to the "50 cent" ook modules we are talking about. note that they normally come in rx/tx pairs for a dollar. even cheaper on alibaba. with some prodding you can get them to sell 2 transmitters instead of one each. of course as usual this is hard to do if you just buy one, so loosen up those purse strings. i never understood people who buy just one of anything. specially things that only cost a buck and take a month to ship like mcus and parts that are easy to fry. what are these guys thinking?

http://www.ebay.com/itm/433Mhz-RF-tr...item2a35eb6201

i went into this further up in the thread but maybe good idea to repeat it here.




2/12/2014

schematic, source, and hex for t13 version 0.4 attached. power control has been added to the original circuit. note that b0 is the power control pin (active high) and beep is b2. use fush=ed fusl=3a so the chip runs it at 9.6mhz instead of factory default which causes 1/8th speed.




3/19/2014

btw recent discussion of morse decoders motivated me to dig up and old project and sure enough i was able to convert the sound sample here into readout on lcd. heres a photo of a version that shows the converted morse audio and above it current position from attached gps. couple characters lower left tell you if you are getting closer or farther away and point north, south, east, or west. naturally a compass in your hand is very useful.


photos:
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Last edited by dave1993; Apr 09, 2014 at 04:47 PM. Reason: t13 fuse settings
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Old Jan 20, 2014, 01:15 PM
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hmmm... im already getting questions about using frs handheld which i guess is more common. i have managed that approach with similar range too but instead of the cheapo ook modules it was necessary to use popular rfm22b which costs couple bucks more. if still interested maybe i can put up some info on that. let me know.
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Old Jan 20, 2014, 02:15 PM
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any chance you can color the components that you added to the schematic?
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Old Jan 20, 2014, 02:35 PM
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Quote:
Originally Posted by dave1993 View Post
im already getting questions about using frs handheld which i guess is more common.
Very good work indeed.

FRS walkie talkies may well be more common, and cheap, but if they dont work at the same frequency as the radio transmitter modules, they wont work.
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Old Jan 20, 2014, 03:44 PM
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Heres the standard list of FRS channels


Channel........Frequency (MHz)......Notes

1 ..................462.5625..... Shared with GMRS
2.................. 462.5875..... Shared with GMRS
3.................. 462.6125..... Shared with GMRS
4.................. 462.6375..... Shared with GMRS
5.................. 462.6625..... Shared with GMRS
6.................. 462.6875..... Shared with GMRS
7.................. 462.7125..... Shared with GMRS
8.................. 467.5625..... FRS use only
9.................. 467.5875..... FRS use only
10................ 467.6125..... FRS use only
11................ 467.6375..... FRS use only
12................ 467.6625..... FRS use only
13................ 467.6875..... FRS use only
14................ 467.7125..... FRS use only
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Old Jan 20, 2014, 04:38 PM
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Cool idea. Could you detail the mods to the module for FM operation? I've got one of those OOK module sets collecting dust and a 70cm HT. Might be a fun little project.
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Old Jan 21, 2014, 01:56 AM
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You mean such combo ?

http://www.ebay.com/itm/433MHz-Trans...-/190949200438

An improvement idea: the Tx could be powered from a lost plane circuit, thus transmitting only when needed
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Old Jan 21, 2014, 06:08 AM
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Quote:
Originally Posted by renatoa View Post
You mean such combo ?

http://www.ebay.com/itm/433MHz-Trans...-/190949200438

An improvement idea: the Tx could be powered from a lost plane circuit, thus transmitting only when needed
this is the one I ordered and they ended up sending two sets
http://www.ebay.com/itm/181210718587
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Old Jan 21, 2014, 04:28 PM
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Quote:
Originally Posted by irun4fundotca View Post
any chance you can color the components that you added to the schematic?
your wish is my command. i attached a new schematic to post #1 showing components required for fm conversion circled in red.
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Old Jan 21, 2014, 04:33 PM
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Originally Posted by srnet View Post
Very good work indeed.

FRS walkie talkies may well be more common, and cheap, but if they dont work at the same frequency as the radio transmitter modules, they wont work.
hi stuart, thanks for the complement. but as far as frs, not quite true:

Quote:
Originally Posted by dave1993 View Post
i have managed that approach with similar range too but instead of the cheapo ook modules it was necessary to use popular rfm22b
as indicated in the table irun posted these frequencies no problem for the rfm22b. as you know its quite easy to accomplish when programmed in direct mode.
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Old Jan 21, 2014, 08:56 PM
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I hate to ask, any chance on a macro pic of the side the components are added to?
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Old Jan 21, 2014, 11:42 PM
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Quote:
Originally Posted by dave1993 View Post
as indicated in the table irun posted these frequencies no problem for the rfm22b. as you know its quite easy to accomplish when programmed in direct mode.
I realise that, my comment was really about the cheap OOK style modules.

There are real cheap, $1-$2, but will likely only be available for the 433/434Mhz region, and not where the LRS sets operate.
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Old Jan 22, 2014, 12:39 AM
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well you can always add a tunable pot to it


in a smaller way of course, the above photo isn't the smallest solution
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Old Jan 22, 2014, 12:45 AM
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Quote:
Originally Posted by irun4fundotca View Post
well you can always add a tunable pot to it
The 'tuneable pot' is probably there to fine tune the modules so that they are closer together in frequency for better performance.

If the pot was capable of changing the module from 433Mhz up to 466Mhz, the adjustment would be so unstable you might never hear the beacon on the walkie talkie.
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Old Jan 22, 2014, 12:57 AM
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ahh ok that makes sence
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