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Raptor30

using cell phones for unlimited range

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can RF be translated into audio and then back to RF?? if it could, couldn't you use a cell phone (on the Heli) set on auto answer to send controls from the ground and send A/V from the Heli?

Furher explanation:

On the ground-- u've got a Futaba 9C with a radio next to with that has a crystal plugged into it (on the same channel as the Tx) so that it receives what the 9CHP is transmitting and is naturally converting it to audio which is being fed into the mic input of your home phone which you use to dial up the cell phone that would be on the Heli

In th air -- u've got the cell phone with it's speaker being tapped by something that would covert the audio back into RF which is broadcasted to the Rx (which is only like 2 inches away). The A/V would be going the other way (frome the cell phone mic to the home phone's speaker.

i know there's gotta be something about this that makes it impossible..

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I know there's gotta be something about this that makes it impossible..

Not impossible at all. It would be good for telemetry, but not for realtime video. For a more plug-n-play project, you could use either a cellular modem (plugs into many of the high-end cell phones) or a cellular transceiver module.

This may interest you:

http://www.ece.msstate.edu/classes/design/...rst,%20v2.0.doc

http://www.ece.msstate.edu/classes/design/...ata%20Specs.doc

http://www.arcelect.com/Telenetics_Cellular_modem.htm

At some point the video equipped cell phones will offer decent enough operation to allow long range license free wireless video. The industry isn't ready for us just yet though.

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so i would have to use a cell-modem? lets forget about the video for now.. and focus on the helicopter's controls. i need a simple, cheap way to have unlimited range and a figured a cell phone would would be the best way...the only problem, i figured, would be to translate the RF waves to audio so they could travel through the cell phone. so the key question is, can RF waves be translated to audio then back again in a SIMPLE, CHEAP way?! ...thanks for the links by the way ;)

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Just have to mention a little boat I saw at last years Hobby Show in Stockholm. It was equipped with cell.phone receiver and could be controlled from anywhere! There was a phonenumber on the boat that you could call and test its functions. The inventor said that it was very hard to control when using your phone buttons.

If I find more details I will let you know.

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yea, thats a lot closer to what i'm trying to do (it's actually simpler) but i want to use my remote instead of push buttons....u can't fly a helicopter with buttons..

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I did think about it but the cost of running it put me off. Also you need a back up system if the cell phone signal fails.

Terry

UK

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I did think about it but the cost of running it put me off...

i can't see how it would cost more than all the stuff you would need for good FPV or to have a good UAV helicopter ststem. just look at all the work and especially money that went into cyber-flyer's setup. think of what you would get; unlimited range; sit in your living room and fly ANYWHERE you want as long as you have enough gas for it. no worrying about trees, buildings interfering with your RF signal or how far away your heli is. IF IT IS POSSIBLE (to send control and receive a/v via a cell phone), IT WOULD BE, BY FAR, MUCH, MUCH BETTER THAN ANY RF SYSTEM.

ps, if you did figure out all the details of what it would take to do it please let us know...

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Hi

you would just need co-pilot and altitude hold to turn on while you redial the #

Thats fine if the signal has failed and you can get it back but what if the mast has been shut down for maintanance, it leaves you with a very poor signal that only shows when you try and land.So at very least you need a return home system and a close range r/c system to land it when its back or may be an auto land system, not so cheap when you think a bit harder. Maybe the coverage is better and the cost of calls is cheaper where you are ? I lose the signal regularly and my local mast fails about twice a year, it may never happen when Im flying but I wont risk it !

You could use a sat phone/link like Global Hawk but what is your requiment and budget ?

Terry

UK

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all i would need is a regular cell phone and some device that can translate the RF into audio (so it could go to the cell on the heli) and then back to RF and that would be the end of it. if it's possible to do what im asking i shouldn't need a sat phone or a cell modem.

i'm not at all worried about dropped calls or the cost of getting a more expensive cell phone plan. it's all WELL worth that risk if it's possible.

so the key question again is; CAN AN RF SIGNAL BE TRANSLATED TO AUDIO AND THEN TRANSLATED BACK? no satellite phone, no cell modem, nothing but a device that will encode the rf into audio and another device on the heli that will do the opposite. if it can be done, i'd love to know how. if it can't then i'll drop the whole idea and start screwing around with antennas, transmitters and ground control setups like everyone else..

Edited by Raptor30

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CAN AN RF SIGNAL BE TRANSLATED TO AUDIO AND THEN TRANSLATED BACK?

Of course.... what do you think is happening when you listen to a radio.

But what I'm asking myself is why do you want to work with RF. Your tx is simply using RF to send a message through. What you are asking to do is to substitute that RF with a cell signal.

So what you really need to do is encode the the pulse train from the TX to audio.

You can tap into it from the trainer cord. That is probably the easiest and least destructive way. Once you have that pulse train you need to encode it to audio. There are several ways of doing this. I'm looking into ways right now to achieve data rates of 9600 baud. But in the mean time I do have a 1200 baud prototype working using a MX614 that I picked up from http://www.glitchbuster.com/

Now if my memory is working this morning (no guarantees here I need to look these up but don't have any references handy) a R/C pulse train is 60 ms. The length of a frame for PCM is 1024 bits.

These numbers may be totally wrong but at least you will get the idea of where I'm going with this.

So let's say at 60ms we need a frequency of 1000/60 = 16.66Hz

at 1024 bits per frame thats.... 17,066.6666

So we need a modem that can handle at least 17066 baud. That might be difficult.

Like I said, my numbers may be way off here... you need to look them up yourself. But this is the way to go about it in my opinion.

Cheers,

Mike

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could you explain, in more detail how your prototype works?

from what i gather you're encoding the data via the trainer port to a packet format so it can be sent over the internet..but i don't understand your problem thoroughly..you can't get it encoded fast enough to be real-time? im sure i could help you out if i can get up to speed.

also my receiver is not PCM. couldn't the RF waves be reproduced from audio?couldn't it be just that simple? couldn't you just have a radio set to receive on 72.xxxMHz and wire it's speaker to the mic of the phone and then on the heli have a transmitter that takes that audio and turns it back into the exact same RF waves? couldn't it be just that simple without going digital and messing around with all that other stuff?

Edited by Raptor30

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First of all my prototype does not encode the pulse train. It's encoding other data. I was simply giving you the name of a chip that encodes a square wave to an audio sine wave.

What you are trying to do is go from a pulse train, which gets encode to RF, decode the RF to audio. Re-encoded it to RF, transmit it to the vehicle, decode it from rf back to audio, decode the audio back to a square wave.

By the way if you go for your ham ticket, all this is required learning. You need to name and know in order all the parts of a transmitter/receiver. And that's exactly what you are talking about when putting an audio wave on top of a carrier.

What I am talking about doing is simply go from the pulse train, to audio, to RF, to audio and back to the pulse train.

Which seems simpler to you?

Basically what needs to be done is remove the RF from the transmitter and replace it with the RF of the cell phone. A lot of the cell phones today have built in modems. Why not simply use that. Decode the pulse train, send it via the built in modem of the phone, to another phone on the vehicle. You make a board the decodes whatever protocol you come up with to control the servos. Now that would actually be quite feasible in my opinion.

You could also use satelites. There are many data satelites up there that you can buy time on. Also quite a few amateur satelites that are free but less dependable.

Look at some of the systems used for sailboats. They have satelite modems.

Edited by mikep

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Basically what needs to be done is remove the RF from the transmitter and replace it with the RF of the cell phone. A lot of the cell phones today have built in modems. Why not simply use that. Decode the pulse train, send it via the built in modem of the phone, to another phone on the vehicle. You make a board the decodes whatever protocol you come up with to control the servos. Now that would actually be quite feasible in my opinion.

i read about what you and cyber flyer are try to do and from what i understand u've been partially successful. would sending/encoding the Tx pusle string at a live rate be possible at this point or is this even harder than what you're trying to do w/ cyber-flyer? you stated earlier that i would likely need a 17k+ packet rate to accomplish this and from what i understand current technology only allows 9600baud. if this is true using a sat phone would be the answer...i guess. i need to figure out the right path to take to successfully turn this idea into reality in the cheapest, simplist way. what components would i need? how would they be wired together? still, though what if you could encode the pulse string into a series of beeps that way they could just be fed, live through the cell's audio and then decoded back into a small simple Tx on the heli? i understand what you're trying to do and the method you're trying to use. what i don't understand is, while even though my idea has more steps, why it couldn't work. you would find which 2 holes (on the buddy port of th Tx) are positive and ground and just wire them directly in place of the mic on phone on the ground. on the heli wouldn't you just take the 2 speaker wires from the cell phone and wire them directly to the mic input of a radio Tx modified to transmit on the freq the heli receives on? right? why wouldn't that method also work?!? it sure as heck would be very cheap and simple...anyway i know you're much more experienced with these things and in the end your answer will probobly be the right answer but i can't give up on this idea until i know exactly why i wouldn't work..

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Raptor

What you want to do is not a problem ! I expect most of us have considered it at some point over the last few years. But at the end of the day you still need a video link which is the limiting factor, so you might as well use a normal ground station.

If you must try it thats fine. You do seem to be confused as to how radio works though, the RF is not the data it only carries the data.

We will all do our best to help you as we all help each other here but we cant do it for you. As far as I know its not availible off the shelf so a certain amount of electronics by you will be nessasary. All the basic parts you need are available, you just need to learn how to interface them with each other, we can help you with suggestions on how this may be done but you will have to make it work.

If you are prepaired to pay there maybe someone on the net who will do it all for you ?

Good Luck

Terry

UK

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I forgot to say speakers and microphones makes it much more complicated not easier, it means you have to convert the data more times.

Terry

UK

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yea, i'll pay no problem but there has to be a well defined fully working system first that can send control and receive video at a decent framerate while still being cost effective by still just using your cell phone minutes. if anyone can do it i'm all for it. i don't understand why a component can't be bought for a cell phone so that it transmits at 56K like everything else. why are we limmited to 9.6k? i'll do whatever it takes to get a system like this working that doesn't use RF. do you realize how cool it would be to just be able to sit in you house and fly ANYWHERE? w/out worring about your RF signal fading away, your only limmitation being how much gas you have? not only that, the person who accomplishes this will have every R/C hobbiest knocking on thier door wanting to buy one. it will make all this RF equipment obsolete..i beleive opening this door would be followed by some quite amazing possibilities

Edited by Raptor30

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Here is what the output from a speaker looks like.. Carlos Santana's Samba Pa Ti in this case.

post-8-1078058798_thumb.jpg

Edited by mikep

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As you can see they are apples and oranges...

Serial data, such as what comes out of a modem is very similar to the PPM wave. That's why I'm saying I bet you could use the built in modem on a cell phone. You would need to design your own "Receiver" which at this point becomes more of a Servo Driver and no longer a receiver since the cell phone is actually the receiver. Basically read in the pulse train from the cellular modem, and output the appropriate pulses to the specific servos.

Somewhere along the way in the R/C TX however, I'm guessing there is a place where the pulse train gets encoded into a sine wave to be mixed into the carrier. I'm not really sure where this is, or even if this is, but I imagine that's how it would work. If you probe around a TX with a scope and you should be able to find it.

Then you can try hooking that into the cell phone.

You will still need to have something on the other end to decode that wave and turn it back into a square wave to read the pulse train and then output the appropriate PWM to the servos. Either that or somehow take the output of the cell phone and put that back on a carrier frequency that the R/C receiver will get.

In otherwords create another transmitter inside the vehicle. That way seems much more complicated then what I have been suggesting in my opinion.

Lastly, I don't know about you, but cellular glitches are frequent where I live. And personally I would trust sending data etc. through cellular bands, but I would never trust it to control my vehicle. All this on many networks these days gets compressed, coverted to digital, decompressed and back to analog etc.

The best bet would be to create a navigation system for the vehicle. Send coordinates to the vehicle by cellular and them have the onboard navigation system actually control the vehicle to that destination. To me that would be the most feasible way to have unlimited range.

Edited by mikep

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you make some very good points but wouldn't the output from the antenna of your Tx look like that of your speaker?? i think it would exept of course they're operating at different frequencies.. so what if you could convert that signal (from the Tx ant.) to something that could pass through the circuitry of the cell phone's mic input without frying it and then, from the output of the heli's cell, convert it back to 72.xxxMHz. you're absolutely right when you said the stream from the Tx BEFORE it gets to the antenna is like apples to oranges to what a speaker's output looks like. BUT if you take it from the antenna instead it would be similar but just at a different freq, right?? is it possible to do it this way or not?

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I don't see it working with the carrier still there. But that's just my guess. And you still need to build a tx from the phone so the receiver picks it up.

Give it a try. Worst case you burn up a phone! ;-)

Edited by mikep

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i've got this little 3 stage fm transmitter i put together and with it came this 'tester' circuit (peaking circuit) which "is simply an RF detector that uses diodes to charge a capacitor" anyway i put it on my 9CAP's antenna and hooked the other end to a speaker. after that it made a low humming niose that CHANGED pitch as each joystick was moved.

can a circuit be built that will cange the carrier wave's freq w/out losing/changing the signal and then have another circuit built that changes it back to how it was orriginally. they're both frequency modulated, just at different frequencies..so why can't a circuit be built to change it's (the Tx's) freq. to an audiable freq. -> send it through the phone then -> a seperate cicuit translates it back to 72.xxx MHz?? it's seems like it should be so simple (and cheap ;) )to do this..am i missing something here??

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yea, i'll pay no problem but there has to be a well defined fully working system first that can send control and receive video at a decent framerate while still being cost effective by still just using your cell phone minutes

We were ok until you said 'receive video at a decent framerate'.

Sorry NO CHANCE !

Terry

UK

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I've thought about this as well.

Agreed that the best way to do it is to make the plane more or less autonomous, and then send course changes and such over a cell modem.

This is the way the Global Hawk and other long range UAVs work, except with a satellite phone modem instead of a cell phone. Looked into satellite modems, but the cost of the air time for one long mission would be $1000s.

Anyway, the tech to do something like this is not hard, but my question is, what is the cell reception like at altitude? My guess is that the cell towers are all optimized for ground level reception and that you'd get all kinds of dropout when you got higher up? Anybody know?

The clever way to implement this would be to have the plane continuously log GPS waypoints as long as it was getting good data from your groundstation, and then if there was a dropout, the plane would circle back to the last known good point of reception .. . . .

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