It’s certainly not the first wireless microphone we’ve ever
published but this one is a little different. First of all it’s stereo,
providing suprisingly good quality sound.
It's easy to build, requires very little setup... and it's cheap! In fact, the low price might turn some people off, thinking it's low quality. Try it - and be pleasantly surprised!
Second, it has a really good range. We tested it at well over
50m and it was still performing very well – noise-free, in fact – but at the
time we couldn’t get our receiver any further away. So it’s likely to have even
better range than that.
Third, it really is simple to build – the hard work (the
transmitter module) is already done for you. It’s just a matter of assembling
the microphone module, which contains the electret mics themselves, preamp and
level controls, and soldering the transmitter module onto it, "piggy back"
style.
Finally, the transmitter module is crystal-locked, so you won’t
have the drift probles of some earlier wireless microphones. And just in case
you were wondering, that doesn’t mean the output is locked to one particular
frequency – it has a nifty synthesis circuit built in to give you the choice of
seven different frequencies between 106.7MHz and 107.7MHz.
On-board preset pots adjust the sensitivity of each channel to
take into account mic differences or if you require different levels in each
channel.
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Typical Specifications
Audio response:.....................20Hz-15kHz.
Channel separation: ........................40dB
Total Harmonic Distortion: ...............0.1%
Output Frequency:...........106.7-107.2MHz
Pre Emphasis: ..................................50μS
DC supply voltage range: ................3-15V
Supply Current: .......................30mA @ 9V
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By the way, the transmitter module is quite capable of
operating at line level if you want just a line level transmitter (eg, to feed
an audio program around your home). Sensitivity is about 100mV. Oatley
Electronics, who designed the kit, have the transmitter module available by
itself if that’s what you’re after. But more on that anon.
You also have the choice of two power supply levels –
3-6V or 7-15V DC. The latter results in a lower current drain. The transmitter
module also has a "5V out" rail to supply power to the preamp module.
Two electret microphone inserts are supplied in the kit. These
can be soldered direct to the PC board to make it a fully self-contained project
or they can be attached to the board via suitable lengths of mini shielded coax
cable. A third option is to use "proper" microphones – they can be electret or
dynamic types – but no provision has been made for plugging these in.