Friday, August 10, 2012

Experiments with Chirp - sending an audio URL....

In amateur radio terms, Chirp is an ambigious term! In this context, we're not talking about your CW transmitter warbling up and down the band and we're not talking about a neat package for programming your handheld.

Two or three weeks ago, Rory Cellan Jones presented an item on the BBC about an application called Chirp that runs on smartphones. It provides the ability to transfer files between devices using audio.

Let's say I've a picture or a URL on my phone that I want to send you. I start the Chirp application on my phone, as do you. I select the photo that I want to send you and press the button. First of all, the application quickly uploads the picture to the Chirp server. Once it's done that, it sends a series of tones which your phone 'hears'. The tones act as like an audio QR code and provide your phone with a URL with which it can access the picture that I uploaded.

Julie and I have been using Chirp to transmit photos between our iPhones and iPads - it's easier than emailling photos back and forth.

The other evening I was talking to David M0TFY on GB3WH and we were talking about Chirp and we wondered whether it would work on the air. After all, how often do you want to send someone a URL or an email address over the air? If you're like me, pretty frequently! Something like Chirp would work well.

Our experiment of using Chirp using our iPhones miked into the radio across GB3WH failed. However, I've a feeling that if we tried simplex we might be more successful - my suspicion was that some of the tones that Chirp uses were not being passed by the audio circuitry of the repeater.

Even if the Chirp application doesn't work over the air (which I think it probably should) - it might be an interesting project for someone to write something that would use tones that would pass over the air readily and robustly to send URLs or eMails...

The Chirp application is free and runs on iPhones. You can read about it here or download it from the App Store.


Anonymous said...

Yeah, this has been done before. It is called RTTY. David

Nick Gilbert said...

I'm not a HAM but are you sure it's not the hight frequencies used? Telephones cut off about 3Khz and chirp uses frequencies higher than this so you can't usually Chirp over a phone line either. Perhaps HAM radios have similar filters on the TX side to limit the bandwidth used per channel?

Tim said...

Nick, yes, I (and the guys who built Chirp) think that's exactly the problem. As you say, 3khz is around the upper limit for our radios too.

I wonder whether a lower set of frequencies could be used for these sorts of applications.

Good to hear from you.


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