2 Mar 2012

SpectrumView for iPod/iPhone

SpectrumView 0-24kHz displays of waterfall and spectrum
Looking around for useful (free) software to help me with VLF and lightbeam tests I came across SpectrumView yesterday. This is a fabulous application for the iPhone, iPod Touch and iPad which provides a 0-24kHz spectrum analyser and a waterfall display.  The app is produced by Oxford Wave Research.

To make best use of this I need to connect an external audio input into my iPod Touch 4g.  A 4-pin jack plug when inserted, rather than a 3-pin one, allows an external audio input (or a mic) to be connected so I can feed my VLF receivers, used for both 8.7-9.1kHz earth-mode comms and for lightbeam baseband/sub-carrier detection, directly into the iPod.  Resolution will be down to around 2Hz at best, so this will be of somewhat limited use, but certainly easier than a laptop for quick field tests or quantitative measurements.

The mic input (on a 4-pin jack) is on pin 4 (nearest the plug cover) and the ground is the next one down the connector (pin 3). The tip (pin 1) and pin next to the tip (pin 2) are the two audio outputs for a headset.

UPDATE 16.3.12: to tell the iPod Touch 4g that an external mic is connected you seem to need to have a 4k7 resistor to ground across the terminals. See later post for details.


Anonymous said...

Thanks Roger! This tip is enormously useful!

Goz said...

Wow thanks! I was just getting round to giving the mic a test. Glad to see its fairly useful on a task it was never originally intended for! :)

Wait for the upgrade soon so that you can pin down frequencies on the spectrogram using pinch-to-zoom.

Oscar (Development Director @ Oxford Wave Research Ltd)

Roger said...

Oscar, I tried with an external audio connection yesterday via a 4 pin jack but could not get the iPod Touch 4g to "see" the external audio input. Did yours work?