Category Archives: Android

APRSdroid without a radio

If you are getting started with APRS, then the easiest was will be to do it on your Smartphone. This post is only about using Android phones, obviously. The clue is the “droid” part of APRSdroid.

NOTE: for this you WILL require an Amateur Radio License and Callsign. If you do not have a Callsign, then I suggest you just watch what is going on on the APRS.FI website.

So you’ve got that this isn’t about iPhones?

Smartphone Guitar interface

Apps such as Garageband on the iPhone allow you to record your guitar noodling and play about with various effects. But first you need to get the guitar connected to the ‘phone.

Looking about on t’internet, there are loads of instructions on how to build a guitar interface for the iPhone, but most involve butchering existing cables.


As the cost of the required AV cables is stupidly high, I decided to just buy the bits and have a go at making one from scratch.

So, lets have a look at what we need:

A 3.5mm 4-pole jack – plugs in to the phone

A 3.5mm stereo socket (case mountable) – for headphones

A 1/4″ mono socket (case mountable) – for the guitar input

Some 3 core shielded audio cable. Sadly, Maplin fucked up and sent me 2 metres of the wrong cable, despite them looking totally dissimilar and having completely different catalogue numbers.

Anyway, sod Maplin, I’m prototyping here. I’ll make do with bits from my wires box.

The first thing to do is solder the cable on to the horrendously fiddly 4-pole plug.  Get the most difficult thing done first, that’s my philosophy.

The pin out for the plug now looks like this:

  1. Green – (Input)
  2. Yellow – (Ground)
  3. Orange – (Output Right)
  4. Red – (Output Left)


Wrap it all up in the casing that came with the plug, and get a “pigtail” lead:

Originally I wanted this lead to be about four inches longer, but this will have to do for the moment. (You can insert a joke here if you really want).

Next, solder up the stereo socket. I went for the same colour code for Ground/Outputs.

Finally, solder-wise, its time to connect up the socket for the guitar input.

Following the same colours from above:

And here it all, all breadboarded up for testing:

After buying a small case, I discovered it was too small to mount the 1/4″ mono socket in, so I had to look about for an alternative.

I haven’t found anything handy yet, but you get the gist.


An old 35mm film container prooved to be the best case I could find. So, now it looks like this: