MAX2606 VHF FM Transmitter

Posted on Feb 6, 2014

To be independent of the local radio stations for testing VHF receivers, you need a frequency-modulated oscillator that covers the range of 89. 5 to 108 MHz ” but building such an oscillator using discrete components is not that easy. Maxim now has available a series of five integrated oscillator building blocks in the MAX260x serieswhich cover the frequency range between 45

MAX2606 VHF FM Transmitter
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and 650 MHz. The only other thing you need is a suitable external coil, dimensioned for the midrange frequency. The MAX2606 covers the VHF band, although the frequency can only be varied by approximately ±3 MHz around the midrange frequency set by the coil L. The inductance values shown in the table can serve as starting points for further experimenting. The SMD coils of the Stettner 5503 series are suitable for such oscillators. In Germany, they are available from BG rklin ( with values between 12 nH and 1200 nH. You can thus directly put together any desired value using two suitable coils. If you want to wind your own coils, try using 8 to 14 turns of 0. 5-mm diameter silver-plated copper wire on a 5-mm mandrel. You can make fine adjustments to the inductance of the coil by slightly spreading or compressing the coil. The circuit draws power from a 9-V battery. The BC238C stabilises the voltage to approximately 4 V. Although the MAX2606 can work with a supply voltage between +2. 7 V and +5. 5 V, a stabilised voltage improves the frequency stability of the free-running oscillator. The supply voltage connection Vcc (pin 5) and the TUNE voltage (pin 3) must be decoupled by 1-nF capacitors located as close as possible to the IC pins. The tuning voltage TUNE on pin 3 may lie between +0. 4 V and +2. 4 V. A symmetric output is provided by the OUT+ and OUT pins. In the simplest case, the output can be used in a single-ended...

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