Walkie-Talkie project

Hi guys,

Im a developer and wanted to try something different. I've never worked with electronic stuff before (despite university) but feel like giving it a shot.

What I want to do is to build a walkie-talkie using Arduino Due/Mega.
I would like to plug the board into my PC and through my mic I would send audio messages (using radio transmitter in my board) and with a walkie-talkie I would like to hear it.

I have few pieces of walkie-talkies handy that I know can communicate in a good range (1 kilometer) so my arduino transmitter/receiver should work with that range too.

Using the boards I've described, how can I integrate such thing? Walkie-talkies usually uses 460-473mhz frequency so do I need to plug any shield in my board?

I need to get the power through my USB (computer) so I can't use more power than a USB can supply. My walkie-talkies uses a 4.5v battery so I don't think that will be a problem as I can power 5v in my boards.

So bottom of line, here's my project:
. Speaks something in my mic (computer)
. Send the audio through USB to my arduino board.
. Arduino will send it through radio frequency (I will specify the channel/frequency).
. Walkie-talkie at other side will be able to listen to the message.
. Walkie-talkie will respond with an audio message.
. Arduino will get the message through radio and send back through USB to my computer.
. The audio will be played through my speakers.

I really appreciate any help. :slight_smile:

Thanks in advance.

Walkie-talkies usually uses 460-473mhz frequency so do I need to plug any shield in my board?

The Arduino isn’t a radio. So, if you need a radio (transmitter and/or receiver), you’ll need extra hardware.

. Send the audio through USB to my arduino board.

How? As audio data that the Arduino can’t handle, or as digital data? Serial data transfer, even at 115200, may be too slow to get voice quality data from the PC to the Arduino.

. Arduino will send it through radio frequency (I will specify the channel/frequency).

What hardware are you planning to use? The Arduino isn’t a radio.

. Walkie-talkie at other side will be able to listen to the message.

A real walkie-talkie? Or another one of your devices?

. Walkie-talkie will respond with an audio message.

No. Audio data is not transmitted. The audio data is converted to digital data, which is broadcast.

. Arduino will get the message through radio and send back through USB to my computer.

OK.

. The audio will be played through my speakers.

Not unless there is some application on the PC that is making that happen.

PaulS:

Walkie-talkies usually uses 460-473mhz frequency so do I need to plug any shield in my board?

The Arduino isn't a radio. So, if you need a radio (transmitter and/or receiver), you'll need extra hardware.

Yes, I'm planning to get RF receivers and transmitters. Do you know any good module?

. Send the audio through USB to my arduino board.

How? As audio data that the Arduino can't handle, or as digital data? Serial data transfer, even at 115200, may be too slow to get voice quality data from the PC to the Arduino.

What's the proper way to handle realtime audio with arduino?

. Arduino will send it through radio frequency (I will specify the channel/frequency).

What hardware are you planning to use? The Arduino isn't a radio.

. Walkie-talkie at other side will be able to listen to the message.

A real walkie-talkie? Or another one of your devices?

At the other side I will have real walkie-talkie.

. Walkie-talkie will respond with an audio message.

No. Audio data is not transmitted. The audio data is converted to digital data, which is broadcast.

. Arduino will get the message through radio and send back through USB to my computer.

OK.

. The audio will be played through my speakers.

Not unless there is some application on the PC that is making that happen.

Yes, I will develop an app for that.

Maybe arduino isn't a best choice to work with in this case?
Thanks

You face many different hurdles... Many hurdles because a "Walkie Talkie" isn't characterised for high speed digital data. The bandwidth of the voice processing circuitry won't handle fast digital stuff.. The modulator is characterised for a 5KHz bandwidth... for the old ones and for the newer radios that can work with as little as 2.5 KHz (Typ) or 1.25 KHz (common) there simply isn't room for a 100 KHz data stream. In FM modulation the bandwidth is the sum/difference between the carrier and the modulating frequency
When you are done? if at all! you will have a Kludge that cannot pass FCC or any of the European frequency management specifications..
You could build a scrambler that would work.. but not legally so in the US. The simplest method is called speech inversion. It's double sideband audio using an oscillator in the audio range to mix with the audio stream and it doesn't require a sync word or a key to unscramble the audio.
It might be possible to "FSK" the carrier which is similar to OOK operation... but the same problem exists in that rapidly turning on and off the carrier occupies the same bandwidth because the bandwidth or the RF spectrum that it would generate is the sum and difference between the carrier and the modulation source...
There is another option to rapidly change the carrier frequency with a DDS source like an AD9850. This can turn your radio into a spread sequence radio, where the carrier rapidly changes frequency... Random number generators with identical PRN sequences are typically used to generate the spread sequence data.. There are many different methods to generate and transmit/receive the signal... All but the scrambler require a radio much better in quality than most all common portable radios. Military Radios are the only real choice for good wide band capabilities and most are against one law or another... Also the simple possession of a device like that.. Could get you summarily Shot until you are thoroughly dead.
I did RF work for nearly 40 years with various types of equipment from CB radios to commercial transmitters for radio telephony.. Paging voice and data, Cellular both AMPS, CDMA and TDMA, mobile telephones and commercial two way radio and low density (200 channel) Microwave data/voice links.
There is one option that I haven't covered and that is a sideband like the one used for FM stereo.. Howeveer it still exceeds the allocated band width of any assignable RF carrier frequency.
You might legally use burst modulation where a segment of an audio stream is stored at one data rate and transmitted at another higher speed data rate.. that solution was a top secret in WWII... 30 seconds of voice is transmitted at 3 to 10 or more times the rate it was stored at creates a high pitch squeal
I'm also an active ham radio operator and my call sign is at the bottom of this response to your original question..
However all but perhaps the speech inversion method are well beyond your level of experience and competence unfortunately..
Some is still beyond my experience too. IHTH and YMMV... IMO.

Doc

Hi,

Thanks very much for the feedback.

Docedison,

Yes, I think it's out of my league such thing, I should start with something simpler. I really appreciate your time and honesty.

Cheers.