These days mp3's have taken over as the primary medium for music. Newer vehicles come with mp3 players and aux jacks to pipe in from your favorite player. I was browsing several DIY transmitters and hacks and decided to carry out my own using the items I had at my disposal.
I started with a Belkin Tunecast, Dlo shuffle dock, and a Kyocera desktop charger for the 7135. I decided to go with a shuffle dock because the price for the accessories are dirt cheap now in the wake of the nano.
As many of you know the Tunecast does the job but the weight of the batteries compared to the size of the shuffle makes it cumbersome to work with, also I have left this unit on too many times killing batteries.
There are other mods out there that increase fm transmission how you do yours is up to you just remember there are FCC regulations to consider. I looked on line and found the proper antenna length to be approx 32".
The Tunecast utilizes a small wire twisted along the audio wire, I replaced this wire with a three foot length of medium gauge wire. Just like other mods the wire was blue and the board was labeled "ant".
The Kyocera charger utilizes a 4.5 vdc 1.5A power supply and since the jack is the same size for the ac and dc power adapters, I can use this unit in the house or car. The dc comes into the pcb and is cleaned and regulated. Also notice the sweet insulated spot to mount the Tunecast pcb. There was the potential to make this unit into a dock/transmitter/charger. But I will use an external usb charger to maintain the integrity of the dock cable.
After some probing with my trusty DVM I found a regulated 4vdc supply. Since the circuit is designed as a battery charger, the current is regulated to adjust for the 1vdc increase compared to the 3volt battery power. Well at least that is my speculation and I'm sticking to it.
After soldering the power to the Tunecast I soldered in a simple 75 cent switch and mounted it in the rear access hole as well. Also you can see the audio cable exiting the battery bay.
Here is the unit put together, the audio fed from the headphone jack to the internal Tunecast and the shuffledock keeps it in place.
The charger has some weight to it and rubber feet, so I dont have to worry about it flying around my truck when I turn a corner. This project took around three hours, and because of all the donor parts and available circuitry the options are endless.