9 Volt FM Transmitter Kit by BC338

This new 9 Volt FM Transmitter Kit can transmit over 900 feet in the open depending on aerial used. The tank oscillator coil is built into the circuit board, and has been tinkered with to give the best distance and stability for it's size. The battery supply rails have been well tied together with respect to radio frequencies. The tracks are also thicker making the fm transmitter circuit a single �solid� block eliminating RF currents in different parts of the circuit. This also means the battery no longer has RF on it which makes the whole unit a lot more frequency stable. Can be tuned anywhere in FM band - DIY Kit 18.

Specifications:

* L: 1-3/4" W: 7/8" H: 1/2"
* Requires 9 Volt Battery
* Transmission frequency is user selectable.
* Transmitter can be listened to on any FM radio.

Read More Source: ( Or Buy kit)
http://www.electronickits.com/kit/complete/surv/ck217.htm
Thank you

VHF Audio Video Transmitter by BF494

The circuit presented here is a simple audio/video transmitter with a range of 3 to 5 metres. The A/V signal source for the circuit may be a VCR, a satellite receiver or a video game etc. A mixer which also operates as an oscillator at VHF (H) channel 5 TV frequency is amplitude modulated by video signal and mixed with frequency mo enna, contains video carrier frequency of 175.25 Mhz and audio carrier frequency of 180.75 Mhz. Then, the transmitter is a B-System of CCIR compatible.

The circuit consists of transistor Q1 with its resonant tuned tank circuit formed by inductor L1 and trimmer capacitor VC1, oscillating at VHF (H) channel 5 frequency. Transistor Q2 with its tuned circuit formed using SIF coil and inbuilt capacitor forms oscillator. The audio signal applied at the input to Q2 results into frequency modulation of 5.5 Mhz oscillator signal. The output of 5.5 Mhz FM stage is coupled to the mixer stage through capacitor C8 while the video signal is coupled to the emitter of Q1 via capacitor C4 and variable resistor Inductor L1 can be wound on a 3mm core using 24SWG enamelled wire by just giving 4 turns. Calibration/adjustment of the circuit is also not very difficult. After providing 12V DC power supply to the circuit and tuning your TV set for VHF (H) channel 5 reception, tune trimmer VC1.

Read More Source:
http://www.newcircuits.com/circuit.php?id=rfr003
thank you

40 Watt Amplifier For FM Broadcast by MRF171A

This amplifier was built based on Marconi's website, A Design for a 40W broadband VHF RF Power Amplifier for FM broadcast. A few minor tweaks were made to the schematic and a few parts were changed to what I had available (mostly surface mount components). The heatsink is from an old Motorola Mostar 800 MHz radio, and has the perfect heatsink island to match the MRF171A. Also used is a Progressive Concepts external LPF7002 low pass filter because it was also on hand. Since the MOSFET uses 28 VDC, I had to homebrew a 28 Volt / 5 Amp power supply using the schematic found in the ARRL handbook.

Tune up went exactly as stated in the how-to, with the RF power output hitting 57 Watts when driven with a stock Broadcast Warehouse 1 Watt LCD PLL transmitter at 98 MHz. Liberal use of ferrite beads and feedthru capacitors are on all RF detector, fan control and SWR control circuits.

Read More Source:
http://www.geocities.com/Area51/Nebula/3736/40watt.html
Thank you.

FM Transmitter 4W by 2N3553

This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable. It is the ideal project for the beginner who wishes to get started in the fascinating world of FM broadcasting and wants a good basic circuit to experiment with.

Technical Specifications - Characteristics

Modulation type: ........ FM
Frequency range: .... 88-108 MHz
Working voltage: ..... 12-18 VDC
Maximum current: ....... 450 mA
Output power: ............ 4 W

Parts List

R1 = 220K
R2 = 4,7K
R3 = R4 = 10K
R5 = 82 Ohm
R = 150Ohm 1/2W x2 *
VR1 = 22K trimmer

C1 = C2 = 4,7uF 25V electrolytic
C3 = C13 = 4,7nF ceramic
C4 = C14 = 1nF ceramic
C5 = C6 = 470pF ceramic
C7 = 11pF ceramic
C8 = 3-10pF trimmer
C9 = C12 = 7-35pF trimmer
C10 = C11 = 10-60pF trimmer
C15 = 4-20pF trimmer
C16 = 22nF ceramic *

L1 = 4 turns of silver coated wire at 5,5mm diameter
L2 = 6 turns of silver coated wire at 5,5mm diameter
L3 = 3 turns of silver coated wire at 5,5mm diameter
L4 = printed on PCB
L5 = 5 turns of silver coated wire at 7,5mm diameter

RFC1=RFC2=RFC3= VK200 RFC tsok

TR1 = TR2 = 2N2219 NPN
TR3 = 2N3553 NPN
TR4 = BC547/BC548 NPN
D1 = 1N4148 diode *
MIC = crystalic microphone

Read More Source : smartkit