Radio Transmitter

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Friday, March 27, 2009

UHF Amplifier for TV Transmitter BLV859

Here's TV RF power amplifier circuit for TV transmitter. A broadband linear amplifier design is presented, suitable for application in TV transposers operating in band IV and V (470 to 860 MHz). The design is based on two BLV859 bipolar transistors combined with quadrature hybrids.

Typical results at the recommended class-A bias point (25.5 V/9.1 A) for the total module include 40 W peak sync output power at -54 dB three tone IMD level (fvision = -8 dB, fsound = -10 dB, fsideband = -16 dB) and an average gain of 10.5 dB in the (470 to 860) MHz range.

The BLV859 transistor is a bipolar linear push-pull power transistor designed to operate in the 460 to 860 MHz range. With a specified output power of 20 W peak-sync in class-A it is the largest device in the new generation of transposer transistors. The intermodulation distortion level is < -54 dB (fvision = -8 dB, fsound = -10 dB, fsideband = -16 dB) and power gain;10 dB at 860 MHz. For application in TV transposers for Band IV/V (470 to 860 MHz) a wideband linear power amplifier has been designed with two BLV859 transistors in class-A.

The amplifier consists of 2 balanced circuits (datasheet), both equipped with a BLV859 and oupled in parallel by means of a wideband 3 dB -90 degree sage wireline coupler at the input and output.

For good thermal contact, heatsink compound should used when mounting the transistors on a heatsink.

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