PSK 31 Apps for smartphones

[Lightspeed]

Useing non-network connected smartphones to code and decode PSK31 signals in a grid down world.

Provided smartphone handset is still functional, even if the mobile phone networks have fallen over, providing we have a means to keep it powered, the phone itself can be used to generate and decipher PSK31 code.

For optimum intended use, the smart phone should be used in conjunction with an SSB mode transceiver, but it will give useful results also when used with FM mode transceivers.

Thought: Handheld FM transceiver + Smartphone make a highly portable field data transceiving station. The sending of data would be short burst with low probability of hostile recipient message decipher, even if they could capture the transmission itself .

Sources of Apps for smartphones (and some screen shots of what it looks like on a phone)

For Android:
http://www.wolphi.com/ham-radio-apps/droidpsk/

For i-Phone £1.99
https://itunes.apple.com/gb/app/psk31/id385619882?mt=8

[OpSecRadio]

I can recommend DroidPsk - that's the one I use on my sony Experia, hooked up to my Boafeng UV-5R with a home made 2m yagi. Relly good results.

[Scythe13]

I think I just realised my folly with our PM's LS.

I thought you meant providing we had means to keep the network powered! I thought that didn't make much sense! Fun with dyslexia haha.

One question, deciphering the signal. Why would it be more secure than a normal transmission?

[Lightspeed]

Hi Scythe,

I thought you'd catch on to this eventually :-)

Re deciphering the signal:

Firstly the signal has to be detected. Its short duration so difficult to catch.

Secondly that signal has to be identified as a PSK 31 data burst. By the time its identified its over

Thirdly, even if the signal is detected, captured and deciphered all that the hostile will have is a series of code letters for example:

r18 5b in 300

This is an approx. 1 second burst of transmission. The decoded plain text still means nothing to a hostile. To the intended recipient it reads

R18 = Checkpoint R18 ( Recipient knows where the checkpoint is so knows direction)

5b = 5 bandits ( raiders)

In = Incoming

300 = ETA at target 300 seconds = 5 minutes.

[Scythe13]

This system is making me all flustered with excitement.

So this app is based on binary sound, so should work on an iPod touch as well as iPhone, iPad and pretty much any android device? Loving it!

It's basically a reinstigation of a text message network! How cool is that?!?!

Providing the text is sent in code, then we have secure, and SILENT (oh hell yeah, that's useful) communication system!

---

For those unsure of how it works, it converts a 'text' written in the app to a binary tone and then sends that tone via the radio (UHF or VHF) to another radio. Providing the other radio has a phone with the same app nearby, the radio will emit the received tone which the app on the phone hears and displays as a text.

App/iPhone--->Radio--------->Radio--->iPhone/App

Really cool system!

[OpSecRadio]

That pretty much sums it up Scythe13 - and it definitely works well, we've had successful comms over 100km using this system with an android phone and a handheld radio hooked up to a small yagi.

A couple of the guys have even used it over a landline - sending PSK31 modulated sounds from mobile to mobile via the landline telephone system (no radio or mobile network) and it worked well, anyone listening in would just think it was a fax signal .

[Lightspeed]

Sythe,

Its not a silent signal on the radio. Its a sound signal, like the sound of a Fax over a telephone line, as OSR described.

The longer the message the longer the duration.

Short messages will take a second or less to transmit.

[Scythe13]

(12 February 2014, 14:28)Lightspeed Wrote: Sythe,

Its not a silent signal on the radio. Its a sound signal, like the sound of a Fax over a telephone line, as OSR described.

The longer the message the longer the duration.

Short messages will take a second or less to transmit.

Sorry mate, should have said "Wordless communication"