TuneCast Range Extensions

After seeing the quick hacks made to the Belkin Tunecast 2 to improve the range by tweaking the antenna from Hack-A-Day, I remembered the forgotten Tunecast (1) stuffed in the armrest of the Oldsmobile. This thing has a maximum range of about eight inches (as measure by my alarm clock/radio) and was incredibly sensitive to everything. I think the biggest problem, however, was the choice of only four channels. In my locale these were pretty much blanketed by one radio station at the very bottom edge of the band.



Removing the two screws in the battery compartment and unsnapping the case brought forth a blue wire, thoughtfully marked ANT by the Belkin folks, and a smallish IC labeled: bh1417e. I finnaly stumbled on the datasheet for this IC and it mentioned the supply voltage ranged from 4 to 6 volts and that that it's made for car audio applications (more on this later). There was also some suspicious looking powder residue on the underside of the PCB, leading me to believe the Tunecast's previous career had been rather shady.

I really expected swapping the antenna out for one more appropriate to the 88.1mhz wavelength would make little difference, considering the unbelievably weak signal present before my tampering (Factory defect? Damage?). I was completely wrong. Soldering a 31.8 inch wire in place of the ANT (the folks at Belkin kindly marked this one for us) connection boosted the range to almost five feet. Pathetic, but a huge improvement over the mere inches of performance it produced with a 5 inch cord. Still, nothing I would consider useful.

This relatively minor adjustment produced such a manifold improvement, I went back to the datasheet for more. The fact that this was being driven far under it's rated voltage begged for correction. The only concern might be overdriving the crystal oscillator, that was running the PLL, to death. Unable to find the exact part for it (or really, any of the SMD's packed into this little board) I had to settle for something resembling it (Bad practice, yes. But this thing is already past due for the junk pile.). That and the higher voltage might just change the frequency of the transmitter to something I couldn’t hope to pick up.

Fortunately, my fears were unfounded. Upped to five volts, even the LED didn't burn out, as I had first imagined. The little device was now producing a loud click to the radio across the room when turned on, without any audio source present. After connecting a tape player, I was able to pick up the voice audio 30 feet away on the living room stereo. Admittedly, it was poor quality and prone to static, but we're competing with a large radio station here, remember? Additionally, it took very careful tuning to get a good signal, though adding an antenna to my receiver might help the whole situation.

All very good, but who wants a tiny FM transmitter that requires a big power supply just to broadcast thirty feet? It was time for major surgery. Stay tuned for next weeks: Butchering the Tunecast (I).