#C200i transistor fm how to

If you buy air- capacitors like the ones furnished in old radios, they can withstand several hundred volts between their plates, if you buy printed-circuit-board-mountable capacitors, they are often times rated at 50 VDC, so as you can see, the standard voltage rating for these components will have you covered. However, I am providing you with some hints in this scenario: All the resistors within the schematic will be required to dissipate less than 1/2 Watt, so you should buy at least 1/2 Watt power dissipation resistors If you plan to plug your transmitter to a +24 VDC source, then you should use 36 VDC rated electrolytic capacitors (C1 and C4), otherwise, 24 VDC rated will do C3 and C5, being Mylar or Polystyrene capacitors, they should be rated at 50 VDC which is a standard voltage value for these types of components C6 and C7 “MUST BE CERAMIC CAPACITORS”… I insist… Ceramic Capacitors, and as such, they are normally rated between 500 VDC to 1 KV last, but not least, we have C8 and C9… variable capacitors come in all shapes and forms, so their final voltage rating will be a function of your preferences. This 2KM FM Transmitter works on low voltage thus, all of its associated components will do too. If you are an absolute beginner, skip this project, get familiar with transistors in simpler applications, then return an build this amazing circuit. I’d like to thank Seetharaman for his nice circuit, it works fine and it’s easy for people who built multiple circuits before this (like myself). Note that this isn’t the transmitting power but the power that is needed to operate, transmitting power depends on the type of antenna (please refer to the literature on RF electronics for the complete details)īecause Q3 (a good old metal case 2N2219 tor) gets bloody hot, I just bought myself a 4 cm fan which is to be installed after my schoolday. I measured the amount of needed curent and it turned out to be 115 mA, with a lab powersupply of 13.8 V, therefore I rate the power P=13.8*0.115=1.6 W.

But thankfully it performs below the stated 2 km in my assembly. I didn’t dare to power this circuit up because of the relatively big transmitting distance (I don’t want law enforcement on my doorstep because I try to learn how radio works:P).

#C200i transistor fm how to

For the RF choke I used a choke inductor of 220 uH, I don’t know how to call it officialy, but it looks like an electrolytic capacitor with radial wiring (leads out of the bottom).įor antenna I used a car whip antanna of approximately 1 m (app. So I assembled it on a piece of general purpose PCB, and it performed just better. Most of the components required for this circuit can be procured from your junk box.Dear Seetharaman, I built this circuit first on a breadboard for testing and it just worked fine.Trimmer capacitor C6 can be adjusted for obtaining the maximum range.L1 can be constructed by making 4 turns of 1mm enamelled copper wire on a 10mm diameter plastic former.Trimmer C5 can be used for adjusting the transmission frequency.If you are going with a battery eliminator, then it must be well filtered and regulated.Using the battery for powering the circuit will improve the performance and reduce noise.The circuit can be powered from anything between 6 to 12V DC.The modulated FM signal is available at the collector of Q2 and it is coupled to the antenna using capacitor C9. Inductor L1 and trimmer capacitor C5 form the tank circuit which is necessary for creating oscillations. R3 and R4 are the biasing resistors of Q2.

Electrolytic capacitor C2 couples the output of the first stage to the second stage. Next stage is the oscillator cum modulator stage built around transistor Q2. C1 is the input DC decoupling capacitor which couples the input audio signal to the Q1 base. This is a collector to base biased amplifier stage where resistor R2 sets the collector current and R1 provided the necessary collector to base bias. The first stage of the circuit is a preamplifier stage based on transistor Q1. This just another one, a simple two transistor FM transmitter. A lot of FM transmitter circuits have been already published here.