DTMF and Arduino for very long range communication

Hi!
I just bought an old Arduino based around the atMega8...

For the first project, I'm trying to make an experimental weather balloon that takes pictures and records temperature data...

But the problem lies in communication system.
I want real-time GPS data to be transmitted to me so i can trace the flight path and also recover the payload easily.
Can you people suggest some method which helps me in data transfer from about 100,000 feet away?

FSK and other digital modulation techniques are quite costly at this level. I do not have a HAM license or equipment so, HAM is also ruled out.

I thought of taking the serial data from the GPS device, send it to Arduino , break it into packets of 4 bits and transmit it using DTMF over the standard FM band (88-108 MHz).
Don't worry about it being illegal ;D

DTMF encoders like MT8880 are cheap and accept four bit input...so, for every four bits that i give from the arduino to the MT8880 would be encoded as a different DTMF tone which can be transmitted over the FM band.
Here, on the base station, I can easily decode it.

Do you think this method would be good ?? ( ignore the illegal part please :smiley: )

Thanks !!

I would suggest not using the standard FM band. Putting the legality issues aside... it would be very difficult to to get a clean signal over those distances. Not to mention it would be interfering with almost every FM radio for miles.

I would suggest using a GMRS radio if you can't use HAM. They can be obtained for a decent price and should have a lot less interference. Not to mention it would get rid of you legal issues.

Also you may need to rethink how far the distance will be. If the weather balloon reaches an altitude of 100,000 feet, that is just the vertical distance. You would need to figure out how far it will travel horizontally, could be several miles, even if you are following it.

I saw an article some time back where the guy wanted the same type of data. In this case he built a data recorder capsule and rather than transmit data back he used a radio locator beacon that activated itself when the balloon came down. I presumed it burst at altitude and the data capsule "floated" down by parachute.
Once he'd found the unit he downloaded the data.
Of course this method is problematic since the device may be out of range, may land in water, may fail to come down within range etc etc
jack

GMRS radio would again be out of my range. the costs are too high. i plan to complete the whole project for under 200$, including the price of a balloon, helium supplies, camera and everything else!
And here in India, it would be nearly impossible to get GMRS modules...

I thought of using 88MHz for the transmission.There's no radio station on it and I don't really care if people intercept the data.

The distance wouldn't me much of a problem. I think a 5 Watt transmitter can be easily heard from about 50 Kilometers away. That is well within the range if i follow the balloon.

Don't you think DTMF can be extracted out of all the noise ?

I would be using beacon as a backup system.

Oh by the way, I'll run out of pins on the board...Is it possible to connect arduino to PSoC (from cypress) ? I know its possible, but just in case any one has done it, and is ready to share the details, half my problems would be solved!

i plan to complete the whole project for under 200$, including the price of a balloon, helium supplies, camera and everything else!

Good luck. Our recent balloon launches (1200g balloon) it cost US$200 for the balloon and helium.

Broadcast FM is wideband FM. This is less efficient, energy-wise, than narrow FM (e.g. ham/commercial FM transceivers). This means you need a stronger signal as compared to narrow FM.

Typical FM broadcast receivers aren't particularly sensitive - they're designed for a radio stations 100kW transmitter with an antenna 500' in the air, not so much for weak signals.

DTMF requires a longer tone and a break between tones. This, too, is much less efficient than, say, 1200baud AFSK (1200 baud packet radio, e.g. APRS).

GMRS radios in the US are pretty cheap. FCC rules prevent modifying them (e.g. adding a high gain antenna) or automatic transmissions (e.g. an automatic beacon or position update). I realize you are not in the US and have a different rulebook, and you've already said you don't care if you operate illegally.

-j

Oh yeah, it's "ham" or "amateur radio", not HAM. There's no acronym, it doesn't stand for anything.

-j

I thought of using 88MHz for the transmission.There's no radio station on it

There might appear to be no radio station on it from the ground from your location but when the balloon is up in the air it can see more of the Earth and there probably is a radio station on that frequency that it will interfere with.

It doesn't matter how slow the communication is.
As far as the power consumption is concerned for high power transmitters, I plan to turn on the transmitter only after it has covered about a quarter of the total height.

As far as the radio stations elsewhere are concerned, let me transmit at 86 MHz.
And i'll make a simple high sensitivity receiver for that frequency and get the data...
Is it possible?

Interesting; this thread seems to indicate the somewhat "out of touch-ness" western society is with the rest of the world.

PsyPi is in India - a country where religious intolerance and social upheaval is rife, a country that has a fairly strict "caste"-based social system that limits social movement, a country that in some cities has problems with its basic trash collection (for some reason, people can't understand trash cans, collection service, etc - and there are "rag pickers" and others - an entire social caste themselves - who make a living at recycling waste and junk seemingly tossed out on the street), a country that, due to religious observances, treat cattle better than their own people, a country where "ship breaking" occurs (one of the nastiest and environmentally damaging practices on the planet - not that western nations don't have their own, mind you!)...

Worrying about whether there is an illegal radio transmission issue would be like worrying about getting caught tapping into a telegraph cable in an 1880's Arizona mining town; nobody will give a good damn.

I am not saying other countries or nations have it better or worse; indeed, there is more tardedness in this species than I like to think about worldwide (damn - I just imagine what we could do as a species if we would get our heads out of our butts, quit being so damn mean to each other over the dumbest and most tarded of reasons and superstitions, and instead work on getting to stars - or at least another nearby planet; hell, I would settle for the moon, an L5 orbit, or even an O'Neill cylinder in Earth orbit - as a species we suck).

:-/

[edit]I want to appologize for the above "long rant"; I am in some kind of funky mood, but that is how I am feeling right now. The above rant has some generalizations that likely have some wrongness in them, I appologize, and PsyPi is welcome to point them out and correct them as needed, since he is a citizen of India...[/edit]

PsyPi is in India

Yes I know and I think you have a rather stereotypical view of the country. I am no expert but I work with a lot of Indian people in the UK and I visited some of them in Bangalore last summer. I was amazed at the degree of poverty sitting along side such vast wealth. I was surprised how education is prized as an exit route from the poverty. I humbled at the way they all tried to make you feel special and important, much much more than you deserved. I was impressed by the way even the most lowly jobs were done with pride and dedication. With so many people crowed together I was surprised there was not more unrest. I was impressed how temple and Christian churches stood side by side. I was terrified at the way they drive on the roads.

My point was that transmitting on unauthorized frequencies is illegal for a very good reason, it will interfere with countless people, that, for some of them, possession of a radio set is something their parents could only dream of.

would be like worrying about getting caught tapping into a telegraph cable in an 1880's Arizona mining town

There's me thinking you got shot for something like that, spying on other peoples claims. None of us are immune from stereotypical views. :wink:

I won't insult your political system :exclamation , because the one I'm in sucks almost as badly. I'm not looking at religion, because I'm sure that its a fire no one can put out and never ends well.

All your television, however, is abominable. Three hundred and nine million people, hundreds of individual channels, and the number of good shows can be counted on the hand of a blind butcher. It's enough to make you buy a cinema pass. :stuck_out_tongue:

I think that's all you're getting, I'm a bit out of practice at insulting generalized people for virtually no reason (I'm sorry, I'll get better).

BTW, You guys seem to forget that the United States till yesterday was one of the most racist nations in the world. A nation which has had segregated schools for blacks till just about three decades ago can hardly be thought of as the best example of freedom. Till yesterday, freedom was only for the whites there.

When you say America is the epitome of freedom, say it to an African American. Chances are that you will have a "jutti" on your face as soon as you say that.
Now try figuring out what that means.Go ask some indians...

America is the same nation which once went to war on black slavery (the American Civil War :question ). At least India never discriminated between fair skinned and darker skinned people when it came to freedom - social , economic or political.

Come to India and you'll know the truth.At least we are dedicated and we care for those who are related to us.
You, Americans let off your children into the wild when they are born.You stop supporting them for education when they turn 15.
And what children you have -- they say they'll call the cops if you even hit them jokingly! They don't care about their parents. Oh parents who have actually never brought them up and never supported them. yeah, i realize why they wanna call the cops :stuck_out_tongue:

would be like worrying about getting caught tapping into a telegraph cable in an 1880's Arizona mining town

Sure, Mr. cr0sh, you got shot for that.Up your a## and out from your mouth, the bullet went.

Anyone has something to suggest about that DTMF thing?

All your television, however, is abominable.

We even have a song about it: "57 Channels and Nothing's On".

FYI, the American civil war was about state's rights vs. federal government power.

Anyone has something to suggest about that DTMF thing?

Yeah, but apparently you don't like what you are hearing. I'll summarize: DTMF over illegal wideband broadcast FM may work, but there are better ideas.

-j

Thanks, kg4wsv.
I've decided to order a cheap GMRS radio and mod it.

I won't insult your political system , because the one I'm in sucks almost as badly. I'm not looking at religion, because I'm sure that its a fire no one can put out and never ends well.

All political systems suck, I agree - basically because there are humans at the controls.

All your television, however, is abominable. Three hundred and nine million people, hundreds of individual channels, and the number of good shows can be counted on the hand of a blind butcher. It's enough to make you buy a cinema pass.

I don't have cable TV - any video entertainment I may watch either comes from DVDs I own, or maybe Hulu or something, and even that is rare. That doesn't mean I don't own a TV; got a 42" LCD hung on the wall, but all its for is DVDs, once again.

I haven't watched real TV since my mom passed away last year (and all she watched was our "custom" 24/7 George Lopez Show channel - DVRs and dementia/alzheimers, what a mix!). Once she passed, we dropped the cable box again (we had dropped it once before) and went back to high speed internet. My wife watches stuff on the various internet TV places scattered across the net, but for me - its a brain drain.

I think that's all you're getting, I'm a bit out of practice at insulting generalized people for virtually no reason (I'm sorry, I'll get better).

As you'll note, I appologized, and deferred to you; I also realize that my viewpoints I stated were generalized, perhaps to a point stereotypical - most of what I know about India has come from reading and media (NPR mainly currently); btw - how did that whole trash collection thing turn out (never heard what happened)?

BTW, You guys seem to forget that the United States till yesterday was one of the most racist nations in the world. A nation which has had segregated schools for blacks till just about three decades ago can hardly be thought of as the best example of freedom. Till yesterday, freedom was only for the whites there.

No - I don't forget it; personally I think humans suck in general. What is really interesting (at least from my American perspective), is how some people in the black community here look upon others with similar bigoted and oppressive views (such as the GLBT community). It seems like everybody has to hate somebody else. There isn't any good reason for any of it (except maybe ignorance, and the inherent sense of literal separateness and aloneness the human animal experiences due to its forebrain).

When you say America is the epitome of freedom, say it to an African American. Chances are that you will have a "jutti" on your face as soon as you say that.
Now try figuring out what that means.Go ask some indians...

I never said America was the epitome of freedom (that's honestly never been true).

America is the same nation which once went to war on black slavery (the American Civil War ). At least India never discriminated between fair skinned and darker skinned people when it came to freedom - social , economic or political.

The Civil War was arguably about individual State's rights, but I forgive you for that error, because most Americans don't really know this and have been educated somewhat differently; I daresay it is almost a "silent reeducation" by our government (by ourselves!) to make the federal government supreme, and ultimately eliminate the concept of an individual sovereign State. In other words, the "united STATES" is supposed to be a union of individual "countries" (the States) bound together under one national flag, but supposedly free to pursue self-interests except where they may interfere or cause problems for others, thus the need and instatement of a federal governmental system to regulate these areas; we have strayed far from this ideal, and one day, it will surely bite us (heck, it already has many times, who am I foolin').

Come to India and you'll know the truth.At least we are dedicated and we care for those who are related to us.

I am certain the same can be said of Americans, just as there are, I am certain, in your country, selfish people who couldn't give a d--m about their relatives and relations. This is another human thing, not tied to any particular nationality, race, or whathaveyou.

You, Americans let off your children into the wild when they are born.You stop supporting them for education when they turn 15.

???

And what children you have -- they say they'll call the cops if you even hit them jokingly! They don't care about their parents. Oh parents who have actually never brought them up and never supported them. yeah, i realize why they wanna call the cops :stuck_out_tongue:

Not quite sure how to respond to this; child abuse isn't a joking matter. That isn't to say that informed children couldn't make their parents lives a living nightmare with one call to child protective services; all it takes in some cases is a simple accusation (but what the children rarely figure on is that they end up "in the system" - foster care - where sometimes, unfortunately, REAL abuse occurs).

Ugly all around...

Sure, Mr. cr0sh, you got shot for that.Up your a## and out from your mouth, the bullet went.

Maybe, maybe not - depends on how far outside of town you were, if you knew what you were doing, what you were doing, etc; by the time anyone cared or got there, you were probably long gone. I have yet to read anything about such incidents; that doesn't mean they didn't occur. It was an analogy, possibly a poor one at that.

Anyone has something to suggest about that DTMF thing?

I would suggest you contact a local ham operator or group; just about any data transmission on any "free" bands is likely either "illegal" or not advised for one reason or another (and I have heard that the hams will find you - or at least the balloon, I suppose). If you don't care about legalities, then you might as well use a shortwave transmitter/receiver set anyhow; you won't be able to get the distance otherwise.

You're already fighting a near lost cause with your budget limitations anyhow...

Good luck.

:slight_smile:

If you can get them, FRS radios are inexpensive and can have a good line of sight range. The below link for near space activities may have some useful info and links for you. As to the off topic comments, public forums often mimic the Rorschach inkblot test, in that no matter the topic of the discussion, people start interjecting what ever issues they have going on in their heads. :slight_smile:

FYI, GMRS is just a slightly more powerful version of FRS. The frequencies overlap and everything.

They're all UHF, just above the US 70cm ham band.

-j