Radio Transmitter for FM Broadcast circuit schematic with description

Here’s easy to build high-quality PLL Radio Transmitter for FM broadcast, with typical output power of 5 W and no-tune design. The transmitter includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD display.
The characteristic of PLL Radio FM Transmitter:
Supply voltage: 11-13.8 V (stabilised or from a battery)
Supply current: up to 1.2 A
Standard frequency range: 87.5-107.9 MHz
Audio/MPX input sensitivity: 2 V pp (for 75 kHz freq. deviation)
RDS/SCA input sensitivity: 0.2 V pp (for 7.5 kHz freq. deviation)
Board dimensions: 109 x 54 mm
PLL Radio FM Transmitter Schematic Diagram

Transmitter Schematic

PLL Radio FM Transmitter Printed Circuit Board

Transmitter Component Layout

Transmitter PCB-Top

PLL Radio FM Transmitter Part list
Q1 – BF240
Q2 – BFG135 (BFG235)
Q3 – 2SC1971 (2N3553) + heatsink
Q4 – BC547B
D1 – SB260 (1N5822, 1N581x)
D2, D3 – BBY40 (BBY31)
D4 – LED 5mm
U1 – 78L09
U2 – TSA5511 (TSA5512, SDA3202)
U3 – PIC16F627A (programmed)
U4 – 78L05
R1, R2, R11, R17, R20 – 10k
R3, R21 – 270R
R4, R15 – 33k
R5, R7, R12, R13, R16 – 680R
R6, R14 – 18k
R8 – 47R (33R if Q2 is BFG235)
R9 – 18R
R10 – 4k7
R18 – 3k3
R19 – 100k smd 1206
R22 – 91R
R23 – trimmer 5k mini
C1, C4, C9, C12, C13, C14, C15, C30, C31, C32, C33, C35 – 10n smd 1206 (C)
C2, C17, C20 – 15p (C)
C3 – 10p (C) (15p if the PCB is single-sided)
C5 – 1n (C)
C6, C28, C29, C34 – 100u/10V (E)
C7, C26 – 10u/35V (E)
C8 – 22p (C)
C10 – 47p (C) (33p if Q3 is 2N3553)
C11, C27 – 100n (C)
C16, C36 – 33p (C)
C18 – trimmer 50p
C19 – 470u/16V (E)
C21 – 4u7/50V (E)
C22 – 330p (C)
C23, C24 – 47p (C)
C25 – 3n3 (P)
L1 – 3.5 turns on 7 mm diameter
L2 – 1uH/815mA choke, or about 10 turns of thin wire on mini ferrite core
L3 – 2.5 turns on 6 mm diameter (4.5 turns if Q3 is 2N3553)
L4, L5 – 3.5 turns on 6 mm diameter
Y1 – crystal 6.4 MHz or 3.2 MHz
TR1 – rf ferrite transformer 2:1 (3:1 if Q3 is 2N3553), see text
SW1, SW2 – button mini
J1, J2, J3 – BNC connector 90 deg.
J4 – power supply connector
J5 – HD44780 LCD standard connector, 2×8 or 2×16 characters
J6, J7 – jumper
Additional information for PLL Radio FM Transmitter
For 0.05 MHz step tuning a 3.2 MHz crystal is required. In other case a 6.4 MHz crystal will make good work (step tuning 0.1 MHz).
Wind all coils (except the L2) by a 0.8 mm wire.
The Y1 package must be tied to ground!
Make sure the Q3 terminals are as short as possible (about 2-3 mm above board). The 2N3553 case/heatsink can’t be tied to ground!
To make the TR1 transformer, use specified number of turns on primary side and one turn on secondary side. The secondary wire should be quite thick but the primary can be as thin as you want. Wind on a 2-hole ferrite (material 61 or N1).
Browse : Radio FM Transmitter for Broadcast on Amazon
See more: Remote Control (RC) Radio Circuit
Source’s more for Pira CZ 5W PLL FM Transmitter

Long range FM transmitter The power output of most of these circuits are very low because no power amplifier stages were incorporated. The transmitte

The power output of most of these circuits are very low because no power amplifier stages were incorporated.
The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres.
The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signals’ power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2.
For better results, assemble the circuit on a good-quality glass epoxy board and house the transmitter inside an aluminium case. Shield the oscillator stage using an aluminium sheet.
Coil winding details are given below:
L1 - 4 turns of 20 SWG wire close wound over 8mm diameter plastic former.
L2 - 2 turns of 24 SWG wire near top end of L1.
(Note: No core (i.e. air core) is used for the above coils)
L3 - 7 turns of 24 SWG wire close wound with 4mm diameter air core.
L4 - 7 turns of 24 SWG wire-wound on a ferrite bead (as choke)
Potentiometer VR1 is used to vary the fundamental frequency whereas potentiometer VR2 is used as power control. For hum-free operation, operate the transmitter on a 12V rechargeable battery pack of 10 x 1.2-volt Ni-Cd cells. Transistor T2 must be mounted on a heat sink. Do not switch on the transmitter without a matching antenna. Adjust both trimmers (VC1 and VC2) for maximum transmission power. Adjust potentiometer VR1 to set the fundamental frequency near 100 MHz.
This transmitter should only be used for educational purposes. Regular transmission using such a transmitter without a licence is illegal in India

FM 9V transmitter circuit with expllanation

This circuit diagram transmitter is a very simple and useful circuit that require few external components and operates in FM band ( above 100 MHz ) .
This circuit diagram transmitter needs to be powered from a 9 volts battery or from another 9 volts regulated power supply .
The tuned coil L1, has two output tappings for the antenna connection, marked "A" and "B". These are both low-level outputs and you choose which tapping you want to use ( stable low range, or more unstable but higher range).
Tap B (2.5%) takes just a very small portion of signal from the oscillator circuit and therefore gives a very frequency stable transmitter. The output level (around 2.5mW) and range are therefore somewhat reduced.

Tap A (10%) delivers very much more power (around 10mW) to the antenna load. This gives you a greater range, but at the expense of frequency stability.
All component leads should be kept as short as possible. The LINK wire on the PCB should
lay flat on the PCB. Use the cutoff from a resistor leg.
Antenna length for circuit diagram transmitter varies with frequency for optimum distance: 90MHz 80 cm, 95MHz 75cm, 100MHz 70 cm, 105 MHz 68 cm.

The frequency determining elements (L1, C5 and C6) form a simple LC tuned oscillator. The inherent problem with this type of circuit diagram transmitter is that any external load (antenna) will change the operating frequency.

Home 9V FM transmitter circuit diagram Radio Frequency This circuit diagram transmitter is a very simple and useful circuit that require few external components and operates in FM band ( above 100 MHz ) . This circuit diagram transmitter needs to be powered from a 9 volts battery or from another 9 volts regulated power supply . The tuned coil L1, has two output tappings for the antenna connection, marked "A" and "B". These are both low-level outputs and you choose which tapping you want to use ( stable low range, or more unstable but higher range). Tap B (2.5%) takes just a very small portion of signal from the oscillator circuit and therefore gives a very frequency stable transmitter. The output level (around 2.5mW) and range are therefore somewhat reduced. Tap A (10%) delivers very much more power (around 10mW) to the antenna load. This gives you a greater range, but at the expense of frequency stability. All component leads should be kept as short as possible. The LINK wire on the PCB should lay flat on the PCB. Use the cutoff from a resistor leg. Antenna length for circuit diagram transmitter varies with frequency for optimum distance: 90MHz 80 cm, 95MHz 75cm, 100MHz 70 cm, 105 MHz 68 cm. The frequency determining elements (L1, C5 and C6) form a simple LC tuned oscillator. The inherent problem with this type of circuit diagram transmitter is that any external load (antenna) will change the operating frequency. The inductor L1 must have around 5.5 turns of enameled 0.5 mm Cu wire , and must have a diameter ( coil diameter) around 5 mm . read more: electroniq.net/radio-frequency/9v-fm-transmitter-circuit-diagram.html

FM 250mW transmitter electronic circuit project with explanation

A very simple FM transmitter electronic project can be designed using this circuit diagram . This FM transmitter electronic project works in FM band and it has a transmission power around 250mW ( thing that make it to work at above hundred meters ) . This FM transmitter electronic circuit is very simple and is based on some common transistors and electronic parts .
T1 transistor can be a BC107, BC171 or equivalent , and is used as an small audio preamplifier that amplify the audio signal from the microphone . Adjusting the R2 variable resistor, audio signal level from the input ( microphone ) can be adjusted until will be delivered to the T1 preamplifier (an over amplified signal applied to T1 can produce an overmodulation) . From T1 , signal is delivered to T2 which form an Hartley oscillator (frequency of this oscillator depends of C8,C9 and L1) .

The transmitter frequency oscillator works in FM band 87.5-108 MHz and can be set , adjusting C8 capacitor and L1 coil . L1 coil must have four turnings on a 0.8-1 mm cylinder support with a 6 mm diameter (space between each wire must be around 1 mm ) .
Antenna used for this project can be a simple telescopic antenna or a 60-70 mm Cu wire .
This electronic project can be powered from a wide range input voltage from 9 to 12 volts Dc ( but can be used even a 18 volts DC .

Latest Mini fm radio Transmitter circuit and Description

Mini fm radio Transmitter circuit

Mini fm radio Transmitter circuit using BF199

This small FM transmitter with a range of about 50 meters designed for hoby. With lots of mini-transmitters then you have a comprehensive, action-packed radio program. Due to the power supply via the USB port of a high frequency stability is achieved. Alternatively, the receiver, a battery 5 to 12 volts to operate.

FM Telephone Transmitter The FM telephone circuit is built on a PC board that is so small it can easily be fitted inside the housing of a telephone m

The FM telephone circuit is built on a PC board that is so small it can easily be fitted inside the housing of a telephone making it an instant pseudo-speak earphone.

Here's the FM telephone transmitter circuit :

This FM circuit connects in series with telephone line, steals power from it, and transmit at both sides of the conversation to an FM radio tuned between 90 and 95 MHz.

FM Telephone Transmitter in Detail.

Crystal Controlled FM Transmitter [Crystal FM Transmitter] The FM transmitter is relatively simple to build and with only one adjustment it is ideal

The FM transmitter is relatively simple to build and with only one adjustment it is ideal for the absolute beginner. But before I continue, let me just make one thing clear. With Wide-Band deviation, the VCO is never locked in phase, only in frequency. It uses a Varicap diode to modulate an oscillator, then lock the oscillator in a Phase Locked Loop, and compare it to a crystal oscillator.

Circuit Basics
The circuit follows that of a simple textbook synthesiser comprising a Voltage Controlled Oscillator (VCO), a damped Loop Filter, a Reference Oscillator (Crystal) and a Frequency Comparator.

The only difference is that I have added a frequency divider chip to divide the VCO frequency by 64. This means that if the VCO operates at 100MHz, the output from the divider will be 1.5625MHz. If the crystal oscillator is also 1.5625MHz then the loop will be "in-lock." The control voltage from the filter to the VCO steers the frequency of the VCO so that the output of the divider is ALWAYS 1.5625MHz. Any deviation from this will result in a change of the loop voltage to move the VCO back to 100MHz.

Audio frequencies are then added to the loop voltage that control the VCO frequency. It is in this way the synthesised transmitter is modulated.

Circuit Specific
I will not delve too deeply into the in's and out's of synthesisers. I have already written several pages of information about them and the stages that are needed to make a working synthesiser.

The specific circuit is shown above. The "Prescaler" (divider) chip needs to have a supply voltage of only 5v (+/- 0.25v) so the LM317 has been included. I used the LM317T due to it's larger can size (and I have got a lot of them) so it will tolerate a supply voltage of greater than 13.8vDC without burning. All has been somewhat over-engineered.

IC1 (CD4001) is the crystal oscillator with an extra gate used as nothing more than a buffer stage. This feeds the frequency comparator of a CD4046 (IC2). The comparator output is filtered with a "slack- handfull" of resistors and caps to feed the VCO; a BC547. A second BC547 has been used to isolate the VCO from the antenna. Without this device the loop would have the tendency to jump out of lock if you touched the antenna. The VCO is also coupled to the divider, IC3, which can be any one of a selection of chips. MB501, SA701, SP8704 and CA12022 are all the same device.

The filter time-constant is a couple of second or so. This makes it take about one second for the loop to stabilise. If this were not the case then the modulating frequency would be seen as a frequency error and the loop would correct the error (remove the modulation). The modulation input is via a 100K resistor and 3n3 capacitor which provides the little pre-emphasis needed for an FM broadcast transmitter. If your AF input comes from a stereo encoder then remove the 3n3 since the pre-emphasis must occur BEFORE encoding. I hope to post a stereo encoder soon, but I give no promisses.

If you are one of those who likes to dissmantle circuits, then you may notice that I have used the CD4046 Signal and Reference the wrong way around - I have used the signal input for the Reference frequency and the Reference input for the signal frequency. This is because the Reference input is designed to be fed from an external source and so it will respond to small small signals (ca: 200mV) whereas the Signal input is designed to be fed from the CD4046s own CMOS logic level oscillator. IC3 is an ECL device with only 1v output signal and is therefore NOT CMOS compatible. The result of this is that the output sense of the frequency comparator is reversed! That is why the Varicap Diode (BB105) is reference to +5v and Not to Ground.

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Continue Reading Xtal-Controlled FM TX (V6)

Using SMD-MP3 FM Transmitter Circuit [SMD MP3 FM Transmitter] With this simple VHF FM transmitter you could play audio files from an MP3 player or co

With this simple VHF FM transmitter you could play audio files from an MP3 player or computer on a standard VHF FM radio. The circuit use no coils that have to be wound. This FM transmitter can be used to listen to your own music throughout your home. When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player.

This FM transmitter uses a chip made by Maxim Integrated Products, the MAX2606 [1] To keep the circuit simple as well as compact . This IC has been specifically designed for low-noise RF applications with a fixed frequency.

The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency.

It is possible to fine-tune the frequency by varying the voltage to the varicap. Not much is demanded of the inductor, a type with a relatively low Q factor (35 to 40) is sufficient according to Maxim. The supply voltage to the IC should be between 2.7 and 5.5 V, the current consumption is between 2 and 4 mA. With values like these it seemed a good idea to supply the circuit with power from a USB port.

A common-mode choke is connected in series with the USB connections in order to avoid interference between the circuit and the PC supply. There is not much else to the circuit. The stereo signal connected to K1 is combined via R1 and R2 and is then passed via volume control P1 to the Tune input of IC1, where it causes the carrier wave to befrequency modulated. Filter R6/C7 is used to restrict the bandwidth of the audio signal. The setting of the frequency (across the whole VHF FM broadcast band) is done with P2, which is connected to the 5 V supply voltage.

The PCB designed uses resistors and capacitors with 0805 SMD packaging. The size of the board is only 41.2 x 17.9 mm, which is practically dongle-sized. For the aerial an almost straight copper track has been placed at the edge of the board. In practice we achieved a range of about 6 metres (18 feet) with this. There is also room for a 5-way SIL header on the board. Here we find the inputs to the 3.5 mm jack plug, the input to P1 and the supply voltage. The latter permitsthe circuit to be powered independently from the mains supply, via for example three AA batteries or a Lithium button cell. Inductor L1 in the prototype is a type made by Murata that has a fairly high Q factor: minimum 60 at 100 MHz.

Take care when you solder filter choke L2, since the connections on both sides are very close together. The supply voltage is connected to this, so make sure that you don’t short out the USB supply! Use a resistance meter to check that there is no short between the two supply connectors before connecting the circuit to a USB port on a computer or to the batteries.

P1 has the opposite effect to what you would expect (clockwise reduces the volume), because this made the board layout much easier. The deviation and audio bandwidth varies with the setting of P1. The maximum sensitivity of the audio input is fairly large. With P1 set to its maximum level, a stereo input of 10 mVrms is sufficient for the sound on the radio to remain clear. This also depends on the setting of the VCO. With a higher tuning voltage the input signal may be almost twice as large (see VCO tuning curve in the data sheet). Above that level some audible distortion becomes apparent. If the attenuation can’t be easily set by P1, you can increase the values of R1 and R2 without any problems.

Measurements with an RF analyzer showed that the third harmonic had a strong presence in the transmitted spectrum (about 10 dB below the fundamental frequency). This should really have been much lower. With a low-impedance source connected to both inputs the bandwidth varies from 13.1 kHz (P1 at maximum) to 57 kHz (with the wiper of P1 set to 1/10).

In this circuit the pre-emphasis of the input is missing. Radios in Europe have a built-in de-emphasis network of 50 μs (75 μs in the US). The sound from the radio will therefore sound noticeably muffled. To correct this, and also to stop a stereo receiver from mistakenly reacting to a 19 kHz component in the audio signal, an enhancement circuit Is published elsewhere in this issue (Pre-emphasis for FM Transmitter, also with a PCB). Author: Mathieu Coustans, Elektor Magazine, 2009

MP3 FM Transmitter Parts List
Resistors (all SMD 0805)
R1,R2 = 22kΩ
R3 = 4kΩ7
R4,R5 = 1kΩ
R6 = 270Ω
P1 = 10kΩ preset, SMD (TS53YJ103MR10 Vishay Sfernice, Farnell # 1557933)
P2 = 100kΩ preset, SMD(TS53YJ104MR10 Vishay Sfernice, Farnell # 1557934)
Capacitors (all SMD 0805)
C1,C2,C5 = 4μF7 10V
C3,C8 = 100nF
C4,C7 = 2nF2
C6 = 470nF
Inductors
L1 = 390nF, SMD 1206 (LQH31HNR39K03L Murata, Farnell # 1515418)
L2 = 2200Ω @ 100MHz, SMD, common-mode choke, 1206 type(DLW31SN222SQ2L Murata, Farnell #1515599)
Semiconductors
IC1 = MAX2606EUT+, SMD SOT23-6 (Maxim Integrated Products)
Miscellaneous
K1 = 3.5mm stereo audio jack SMD (SJ1-3513-SMT
CUI Inc, DIGI-Key # CP1-3513SJCT-ND)
K2 = 5-pin header (only required in combination with 090305-I pre-emphasis circuit)
K3 = USB connector type A, SMD (2410 07 Lumberg, Farnell # 1308875)

Notice. The use of a VHF FM transmitter, even a low power device like the one described here, is subject to radio regulations and may not be legal in all countries.

Source: MP3 FM Transmitter Circuit

Circular FM Broadcast Antenna In the world of RF, the antenna is one system that is very important because the antenna can determine how far the sign

Circular FM Broadcast Antenna

In the world of RF, the antenna is one system that is very important because the antenna can determine how far the signal goes. The antenna is an element which radiates the signal. Electromagnetic field signals can be polarized in a circular, vertical, and horizontal. Here is the FM broadcast antenna is circularly polarized, is used in FM transmitter in the frequency range 88-108 MHz.

Antenna and Material Specifications

Antenna made of copper pipe (pipe AC), the reasons for using these materials are easy to create circular shapes. Diameter copper pipe is 0.5 “.

Circular FM Broadcast Antenna

This antenna has a gain of about -1.5 dB (isotropic dipole). Increasing the amount of gains made through stacks of more than one antenna. More and more antennas are stacked, it will increase the amount of gain antennas, so that will be able to double the ERP (Emmition Radiating Power).

Antenna Dimensions

For the antenna size can be seen on circular FM broadcast antenna diagram below:

Circular FM Broadcast Antenna Diagram

Signal amplification

Gain is based on the antenna gain in Decible (dB). ERP is calculated by multiplying the power of the transmitter with antenna gain. When four antennas stacked estimated to have a 3:12 dB gain, 5.12 dB for six antennas, and 6.40 dB for eight antennas. (3dB= 2, e.g. Antenna Gain for eight antennas =6.40/3 x 2 = 4.26)

ERP = Transmitter Power (Watt) x Antenna gain.

Read more : Dipole FM Antenna – FM Radio Transmitter.

13.8V 20A DC Power Supply The following DC Power supply circuit is a linear power supply (using transformer). The voltage output of 13.8V power suppl

13.8V 20A DC Power Supply

The following DC Power supply circuit is a linear power supply (using transformer). The voltage output of 13.8V power supply is highly regulated, can be adjusted in the moderate range, at up to 20A continuous current. This power supply is suitable for use for amateur radio equipment. DC Power supply is easily constructed and suitable for heavy duty because it is very efficient, small and lightweight.

In the DC power supply presented here, the pass transistors are located in the negative rail and connected in common-emitter configuration rather than as emitter-followers. Thanks to this, the regulator’s minimum voltage drop is extremely low, only about 0.1V for the transistors plus 0.5V for the equalizing resistors.

DC Power Supply Circuit

The other advantage is that the collectors are directly connected to the negative pole of the power supply’s output, which in most applications is grounded. That means that no insulation is required between the transistors and the grounded power supply cabinet! This eases the cooling very considerably. Thanks to the low regulator drop, a low cost 25V filter capacitor can be used.

Some Notes of DC Power Supply Circuit

• Use a transformer for the primary voltage you need. The 3A fuse is for 220 or 240V primaries. If you use something in the neighborhood of 110V, use a 6A fuse.
• The rather high transformer rating of 35A accounts for the losses that occur due to the capacitive input filter. If your transformer is rated for capacitive input, then a 25A value is enough.
• Of course you can make up C1 by placing several smaller capacitors in parallel. Likewise, the 0.1 Ohm, 5 Watt resistors can be made up by several in parallel, for example by 5 resistors of 0.5 Ohm, 1 Watt each.
• The LM336Z-5.0 voltage reference IC should not be replaced by a zener diode. Zeners are not nearly as stable. A different voltage reference IC can of course be used, if R2 and R3 are modified for the different voltage.
• D1 and Q2 through Q6 need heatsinking. Only Q2 needs insulation. D1 dissipates up to 60W, Q2 up to 25W, while the pass transistors dissipate up to 30W each in normal use, but may reach a level of 130W during short circuit! Take this into account when choosing the heat sink!
• R5 exists only to make sure that the transistors can actually be driven off. The 741 is not a single-supply operational amplifier, so it cannot drive its output very low. If a true single-supply opamp is used, then R5 becomes unnecessary.

See more: VHF Radio Transmitter – FM Radio transmitter.

ne Transistor FM Radio Receiver Circuit FM Receiver Here’s simple FM receiver circuit for a simple superregenerative FM radio. It is sensitive, sele

ne Transistor FM Radio Receiver Circuit

FM Receiver

Here’s simple FM receiver circuit for a simple superregenerative FM radio. It is sensitive, selective, and has enough audio drive for an earphone. These designs generally have low component counts, however the design or my construction have been far from simple.

FM Receiver Schematic

FM Radio Receiver Circuit Layout
Because this is a superregenerative design, component layout can be very important. The tuning capacitor, C3, has three leads. Only the outer two leads are used; the middle lead of C3 is not connected. Arrange L1 fairly close to C3, but keep it away from where your hand will be. If your hand is too close to L1 while you tune the radio, it will make tuning very difficult.

Winding L1

L1 sets the frequency of the radio, acts as the antenna, and is the primary adjustment for super-regeneration. Although it has many important jobs, it is easy to construct. Get any cylindrical object that is just under 1/2 inch (13 mm) in diameter. I used a thick pencil from my son’s grade school class, but a magic marker or large drill bit work just fine. #20 bare solid wire works the best, but any wire that holds its shape will do. Wind 6 turns tightly, side-by-side, on the cylinder, then slip the wire off. Spread the windings apart from each other so the whole coil is just under an inch (2.5 cm) long. Find the midpoint and solder a small wire for C2 there. Mount the ends of the wire on your circuit board keeping some clearance between the coil and the circuit board.

A tuning knob for C3

C3 does not come with a knob and I have not found a source. A knob is important to keep your hand away from the capacitor and coil when you tune in stations. The solution is to use a #4 nylon screw. Twist the nylon screw into the threads of the C3 tuning handle. The #4 screw is the wrong thread pitch and will jam (bind) in the threads. This is what you want to happen. Tighten the screw just enough so it stays put as you tune the capacitor. The resulting arrangement works quite well.

FM Radio Receiver Circuit Adjustment
If the radio is wired correctly, there are three possible things you can hear when you turn it on: 1) a radio station, 2) a rushing noise, 3) a squeal, and 4) nothing. If you got a radio station, you are in good shape. Use another FM radio to see where you are on the FM band. You can change the tuning range of C3 by squeezing L1 or change C1. If you hear a rushing noise, you will probably be able to tune in a station.

Try the tuning control and see what you get. If you hear a squeal or hear nothing, then the circuit is oscillating too little or too much. Try spreading or compressing L1. Double check your connections. If you don’t make any progress, then you need to change R4. Replace R4 with a 20K or larger potentiometer (up to 50K). A trimmer potentiometer is best. Adjust R4 until you can reliably tune in stations. Once the circuit is working, you can remove the potentiometer, measure its value, and replace it with a fixed resistor. Some people might want to build the set from the start with a trimmer potentiometer in place (e.g., Mouser 569-72PM-25K).

Browse : FM Receiver on Amazon

See more: MP3 FM Transistor

Source: Build A One Transistor FM Radio

Synthesised WideBand FM Transmitter

This project is a complete crystal-controlled Wide Band Frequency Modulated (WBFM) transmitter delivering a power output in the order of 10 milli-watts (+10dBm) using simple components. The transmitter is based upon the Phase-Locked Loop (PLL) principle, but due to the circuit's simplicity a true "phase lock" can never be achieved.

The transmitter has both 1v peak-to-peak 'LINE' input and 10mV 'MIC' audio inputs. These will accept audio input sources from external equipment, such as hi-fi, CD and computer equipment. The microphone input also has an in-built power source to energise an 'Electret' type condenser
microphone. The Radio Frequency (RF) output circuitry includes a three-pole filter for reduction of harmonics and other spurious signals. The spurious output signal level is better than -40dBc (0.0001 times the power of the wanted signal level), which makes the project suitable for driving an external power amplifier.The transmitter is powered from a 12v supply, but it will operate from 9 Volts to 16 Volts. The DC power input is equipped with a diode (D1), which protects the transmitter in the event the supply voltage is inadvertently connected the wrong way round.

Download Kit Intro Datasheet

FM STEREO TRANSMITTER with BA1404

NEw STEREO FM TRANSMITTER WITH I.C. BH1417

STEREO FM TRANSMITTER WITH I.C. BH1417

This is the latest BH1417 Stereo Encoder design from RHOM that includes a lot of great features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference and crystal based stereo encoder for stereo transmission.

BH1417 can be supplied with 6 - 15V voltage, consumes only around 25mA while providing very sound quality and improved 40dB channel separation. BH1417 is only available in SOP22 IC case and this may be an inconvenience for some folks.

On the other hand, because the chip is smaller than regular DIP-based ICs it is possible to fit the entire stereo coder on a small PCB.

BH1417 requires 7.6MHz crystal oscillator which is pretty hard to find. The good news is that you can use 7.68 MHz crystal instead. In fact our BH1417 stereo encoder prototype uses 7.68 MHz crystal.

This has absolutely no effect on stereo encoding process, we have tested it and stereo sound is crystal clear.

Specifications:
Supply Voltage: 9 - 16V
Transmission Frequency: 87.7 - 88.9MHz, 106.7 - 107.9MHz (200kHz steps)
Output RF Power: 20mW
Audio Frequency: 20 - 15KHz
Separation: 40dB
Power Consumption: 30mA

Frequency Selection / Calibration
Frequency selection is very straight forward. Simply select transmission frequency at which you would like to transmit, set the combination for 4-DIP switch and BH1417 will immediately tune to that frequency. If you can't hear the transmitted audio signal on your FM receiver then re-adjust 2.5 turn variable coil until you can hear the signal. If you have a laboratory power supply you may try to vary the voltage supply from 9 to 16V. While doing that BH1417 will automatically vary the voltage for MV2109 or ZMV833ATA varicap diode making sure that there's no frequency drift.

New FM Stereo Transmitter ( BH1415F )

This Electronic circuit is a stereo FM Transmitter based on BH1415F wireless audio link IC. Phase Locked Loop (PLL) controller use PIC16F628 and the the PLL frequency programming can be displayed with 8x2 and 16x2 LCD. Frequency Range 88-108 MHz

BH1415F can be supplied with 6 - 15V voltage, consumes only around 25mA while providing very sound quality and improved 40dB channel separation. BH1415 is only available in SOP22 IC case and this may be an inconvenience for some folks. On the other hand, because the chip is smaller than regular DIP-based ICs it is possible to fit the entire stereo coder on a small PCB.

Download Full Documentation With PCB
BH1415F Datasheet
Sourc:

http://kitaudio.blogspot.com/2010/06/fm-stereo-transmitter-bh1415f.html

Build BH1417 Stereo PLL FM Transmitter

This is the latest BH1417 FM Transmitter design from RHOM that includes a lot of features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, stereo encoder for stereo transmission, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference, PLL circuit that provides rock solid frequency transmission which means no more frequency drift, FM oscillator and RF output buffer. Link

for MP3 Player FM Transmitter

Do you have an idea to create your own radio station, transmit the music around the house, or simply create a wireless link between your iPod and a receiver in your car, this transmitter will let you do these things easily. With BA1404 HI-FI Stereo transmitter you will be able to transmit MP3 music from your iPod, computer, discman, walkman, and many other audio sources. This FM transmitter design is a result of many hours of testing and tweaking. The goal was simple; to test many existing BA1404 transmitter designs, compare their performance, identify weaknesses and come up with a new BA1404 transmitter design that improves sound quality, has very good frequency stability, maximizes transmitter’s range, and is fairly simple for everyone to build. We are happy to announce that this goal and expectations have been met and even exceeded.

FM Transmitter Schematic

The transmitter can work from a single 1.5V cell battery and provide excellent crystal clear stereo sound. It can also be supplied from two 1.5V battery cells to provide the maximum range.

FM Transmitter Printed Circuit Board
This a suggested high-resolution PCB layout for BA1404 Transmitter. It is ready for printing and no further adjustments are necessary. Dimensions of the PCB should be 57 mm x 35 mm (W x H).

FM Transmitter PCB

Browse: MP3 FM Transmitter on Amazon

See More: Audio Video Transmitter

Source: BA1404 Stereo FM Transmitter

NJM2035 Stereo Encoder / Multiplexer Kit

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This package comes with components and instructions that are needed to build simple but high quality stereo encoder. The circuit connects to any mono FM transmitter and converts it into HI-FI stereo transmitter. The project can be supplied with as little as 1.2 Volts, up to 3.6 Volts. The circuit also has built-in stereo pre-emphasis to enhance and produce a crystal clear sound. NJM2035 is manufactured by NJR CORPORATION (JRC), a subsidiary of New Japan Radio, a company that is known as the world's best manufacturer of high end professional audio semiconductors.

Component List
1x NJM2035
1x Stereo Encoder PCB
1x 38KHz Crystal
1x 33uF Capacitor
1x 10uF Capacitor
3x 100nF Capacitor
2x 1nF Capacitor
1x 100pF Capacitor
1x 10pF Capacitor
1x 82K Resistor
2x 47K Resistor
2x 27K Resistor
1x 10K Resistor
1x Schematic with Instructions
read more source:http://electronics-diy.com/store.php?sel=kits&sub=fm_transmitters

500mW FM / VHF Transmitter Amplifier / Booster (Parts)

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This is a high performance low noise 500mW amplifier / booster for all low power FM transmitters such as BA1404, BH1417, BH1415, 433MHz transmitter modules, etc. The amplifier chip is an integrated circuit containing multiple transistor stages and all other parts conveniently within a single small package. Boosting your FM transmitter has never been easier and the output signal can also directly drive 2n4427 or 2n3886 transistors for 1W or 5W of RF output power.

Specifications
Output Power: 500mW
Input Frequency: 50MHz - 1300MHz
Voltage Supply: 9-12V

Component List
1x High Performance FM / VHF Amplifier Chip
1x 10uH Choke
1x 220 Ohm
3x 1nF Ceramic Capacitor
1x Instructions and Schematic
source:http://electronics-diy.com/store.php?sel=kits&sub=fm_transmitters

BA1404 HI-FI Stereo FM Transmitter Kit circuit

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Be "On Air" with your own radio station! BA1404 based transmitter is an exciting product that will broadcast high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground. Add our 500mW FM / VHF Transmitter Amplifier / Booster for even longer range.

The circuit is based on the popular BA1404 stereo broadcaster IC which contains all the complex circuitry for generating the stereo FM signal. 38 KHz crystal provides a rock solid stability of sub-carrier for stereo signal. PCB includes green solder mask layer for easier soldering and protects wires that do not need soldering.

Kit Components
1x Printed Circuit Board [5 cm x 3.2 cm]
1x BA1404 Stereo FM Transmitter IC
1x 38KHz Crystal Oscillator
1x 3.5T Variable Precision RF Coil
1x 10uH Inductor
4x 10uF/35V Capacitor
4x 1nF Ceramic Capacitor
2x 1nF Mylar Capacitor
1x 220pF Ceramic Capacitor
5x 10pF Ceramic Capacitor
2x 47K Resistor
2x 27K Resistor
1x 150K Resistor
1x 5.6K Resistor
1x 270 Resistor
1x Instructions
source:http://electronics-diy.com/store.php?sel=kits&sub=fm_transmitters