Interesting modulation
So this week I borrowed a set of Torx™ drivers to take the fascia off my pug 206… My mission was to install an FM Modulator to allow me to connect my MP3 player to the stereo.
First I’ll explain what an FM Modulator is (for those who don’t know already). FM means “Frequency Modulation” and this means that an radio signal is generated at a specific frequency (like 99.7 MHz for radio 1 in NI) and then audio information is added to it by modulating this signals frequency above and below that frequency.
So what an FM Modulator does is take an audio signal and do this to it. The difference between this and a transmitter is that it doesn’t broadcast the signal, simply passes it down a wire plugged into an aerial socket. These kind of things are used in VCRs to allow the user to tune the telly into it (pre-SCART). In this case it’s plugged into my car stereo to fool the stereo into thinking theres another radio station to tune into and play back the audio signal I put in.
Simple eh?
My first issue was that there was a problem with the aerial pass through connectors (this thing sits between the car antenna and the radio unit) so while it was connected there was no signal coming from the antenna, so all the radio stations were just fuzz. I resoldered it and it was fine.
The second problem arose when I found that, despite all the promises of the box, when this thing is on the other stations do get affected by the strong signal it produces. So I had to uncover the switch I had left to be switched on under the car trim. (It is wired to the cig-lighter socket which is switched with the ignition, so it is always off when the car is off).
The next problem I came upon is that this wiring somehow fools the car into thinking that they keys are still in the socket even when taken out. This in turn stops you from locking the doors via central locking. Not when it is turned on, but when it is turned off! I don’t quite understand this yet, except that it must be interfering with the incar computer somehow… any clues folk? Or anywhere else I could wire it to to avoid this problem? Initially I had thought that I could hook it to the radio power lines, but I have heard problems relating to that in Peugeots, but if I can find a regular power lead then I will fix it up to that maybe…
the nex issue I have come across is that my iPAQ which I had hoped to use to play MP3’s with has a slight hiss coming out that you just don’t notice on headphones or through regular equipment. But the FM Modulator seems to amplify the hiss more than the tunes being played. I am going to fiddle with it a little tomorrow and see if I can adjust the levels on the modulator to fix it.
If not I will just have to stick with the Zen I salvaged from my brother last week as my MP3 player, I was just coming around to the idea of selling it too and having just one gadget to carry about…
Also, not related, but if I end up able to use my iPAQ I’d like to be able to sync it with media player (11) via bluetooth as the USB 1.1 connection is unbelievably slow (it should be upto 11Mbps but isn’t…)…
So these are the problems of geekhood and too much time on my hands!



