Belkin TuneCast™ II
This item is similar in appearance, but in actual fact, markedly different to the ChaoYu badged transmitters. There are a few immediate external differences between the two devices. The TuneCast™ has only three
buttons on the front, and has a different display.
It also has a different power connector and takes 12v directly into the unit,
the voltage regulator is built in. The printing on the side of the unit
indicates polarity, voltage and declares that it requires 200mA which seems a
little on the high side.
The TuneCast II features one extra memory channel (4
instead of 3) and covers 88.1MHz - 107.9MHz instead of 87.5 - 108MHz. The Belkin
has an audio activated TX on/off function with 60 second delay and a low battery
LED but no real time clock or thermometer. (I'm sure TuneCast owners can suffer
that loss)
This is believed to be one of two devices used by Ofcom
for SRD Testing
TuneCast Modifications
There is an external site which has a couple of
modifications for the TuneCast
II, including an add on PA.
More stuff also on Instructables.
The second article is more convincing (This guy even knows how to solder) and includes some decent illustrations.
In another article all the
writer wanted to do was make a jerk out of himself by jamming broadcast
stations. I'd avoid his USB power mod like the plague too. If you want to make
an incenduary device out of your TuneCast then this is the mod for you,
otherwise I'd leave well alone and use the socket that's already there.
These all seem to show that the TuneCast has an antenna
which is built into the four conductor signal lead and is not shared with any of
the three wires which are used for the audio signal itself.
More importantly to me, they show that this device is
quite different inside to the ChaoYu devices
 TuneCast I
There is or was another model from Belkin called the
TuneCast , shown to the left in its retail packaging. It was a 'no display' type with four fixed frequencies,
88.1, 88.3, 88.5 or 88.7Mhz. It's possibly the other device (15nW) Ofcom based their
SRD tests on
The internal guts of the version 1.2 device
Here you see the blue wire is the antenna and the signal lead is in fact four
core. The chip to the left is assumed to be a stereo encoder.
At the top of the board pictured below are a few power related components.
From left to right, electrolytic smoothin capacitor, wires from batteries, input
socket, regulator and inverse protection diode.
Only one crystal seen on this unit next to what I presume is the PLL chip. We
won't expect to see a RTC crystal as this unit does not have a clock feature.
The black blob covers the microcontroller chip which handles the display and
logic functions.
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