Sunday, September 18, 2011

Audio Video Transmitter

The above diagram of a transmitter circuit television. Video input jack J1 first termination resistor R6 and capacitor C1 connected via clamping diode D1. Clamping forces sync pulses to a fixed DC level to reduce the effect of flowering. Potentiometer R3 is used to set the video signal of winning, its effect is similar to adjust the contrast of the TV. R7 bias can be adjusted to control the image of the black level, so that at a certain level, the signal is sent, the image even in total darkness. This TV receiver can maintain a proper synchronization. When we arrive, the potentiometers R3 and R7 are adjusted for cross-best all-around performance. RF transformer T1 and its internal capacitor form a tank Hartley oscillator circuit that is tuned to 4.5 MHz. Audio input signals to J2 is connected to the bottom of the C2-D3 and R4: the audio signal modulates the subcarrier signal that Q3 provides audio, s 4

5 MHz above the video carrier frequency. FM-modulated subcarrier applied to the modulator section C5 and R9. Resistance R9 adjusts the level of the subcarrier from the video signal. The transistors Q1 and amplitude modulated video and audio signals Q2 on a RF carrier signal. The primary frequency is set by the coil L4, which is 3.5 turns 24 - enameled wire on a form containing a ferrite coil slug.That standards is part of a Colpitts tank circuit also contains C7 and C9. The tank circuit forms of network so that responses Q4 Q4 turns on the RF output to adjust the frequency of the oscillator section is amplified by Q5 and Q6, the voltage from the modulator section. Adaptation of the antenna and low-pass filtering is performed by C12, C13, and L1. Resistor R12 is optional, it is added to help match the output of another antenna.


Before going further, while it is certainly possible to build the machine from scratch. But unless you're an experienced builder and hangers-qualified parts, it is strongly recommended to buy the full game, or at least, the kit component of the source included in the list part. While most parts are readily available, some can be a real headache to do.

The 4.5 MHz RF transformer (T1) used in the kit is an OEM Toko is not available through traditional sources. Although nearly all 4.5 MHz RF transformer is similar to that described in subsection (internal capacitor, hit secondary) can be used, these units are difficult to obtain an amateur friendly source. If you are determined to follow this path, it is best to contact Toko (1250 Feehanville Dr. Mt Prospect, IL 60056, Tel 708-297-0070 ..) for the location of your nearest dealer of the full range . In addition, the coil L4 is a unit of measurement. However, it can be done at home with the parameters listed above. The transmitter must be incorporated into a PC card for better performance. You can make a pension from the template sheet provided in Fig. 2, or use that comes with the kit. The parts are installed on the motherboard as shown in the chart location of the parties [see Fig. 3). Pay special attention to the orientation of the transistors, electrolytic capacitors. and the diode.

Outline the switch (S1), which is shown in Fig. 3 is the same with the switch, SPST button kit, which is normally open. You can use any switch to an alternative. A simple style fits the Board of Directors with a screw machine: stylus is ideal for many applications. Battery holder can be soldered onboard jumper or install a piece of wire or doublesided tape screws.When board is ready to be installed in the case. If available in the Ramsey Electronics installed allows the government down, and lift the top, yet harmonized. It also protects against the bottom edge of his shorts during alignment. You should check the solder side of the government thoroughly before installation, in the case.

D1—1N914 silicon diode
Q1-Q—2N3904 NPN transistor

(All fixed resistors are 1/4-watt, 5% units .)
R1, R2, R11—1000-ohm
R3, R7—1000-ohm trimmer potentiometer, PCmount
R4, R9, R10—10,000-ohm
R12—75-ohm (optional, see text)

C1, C8—100-mF, 16-WVDC, electrolytic
C2—2.2--mF, 50-WVDC, electrolytic
C3-C6, C11, C14, C15—001-mF, ceramic-disc
C7, C9—2.2-pF, ceramic-disc
C10—100-pF, ceramic-disc
C12, C13—68-pF, ceramic-disc

ANT1—Antenna, telescopic-whip
B1—9-volt battery
J1-J3—RCA jack, PC-mount
L1—0.15-mH miniature inductor
L2, L3—2.2-mH miniature inductor
L4—0.14- to 0.24-mH adjustable, slug-tuned coil
(see text)
S1—SPST, push-button switch, normally open
T1—4.5-MHz 1F-can-style RF transformer

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