My name is Saikat and I’m writing you from Singapore
I came across your very useful article (link here) in Embedded World when looking for information for my son’s science project. Some of the terms were difficult, so I wondered if you would be kind enough to spare a minute to help me?
Project description: To set up a morse-code channel using only 2 standard cellphones without using the cellular network or wi-fi
Theory: A mobile app will do the following:
- Get cellphone # 1 to send a Morse signal via the speaker, but on ultrasonic or RF frequency across a distance of 5-10 kilometres
- Get cellphone #2 to receive the Morse signal via its microphone and translate it into English alphabets on the screen
What I need your advice on:
- Whether an average cellphone battery (3.5 V, 7.98 Wh, 2100mAh) and earpiece is capable of transmitting an ultrasonic or RF signal powerful enough to reach across 5-10 km
- Whether the average cellphone speaker and microphone can detect such a signal
- If not, is there any signal on any frequency which the average cellphone can transmit that would cross 5-10 kilometres?
Please accept my thanks for your help, and for taking the time to go through my mail. I look forward to your reply.
With thanks and regards,