Sideband

t mhjj

Fig. 3. Ideal TV transmission characteristics, t mhjj modulation, the cathode must be grounded well for rf but not for video, 1 [se good button bypasses of 10-40 pF.

The rf exciter

Fig. 2 shows a block diagram of the K3ADS television exciter. Two things are evident. First the transmitter is a combination of units that have appeared in print. The low level exciters are the 220 units appearing in the older editions of the ARRL Handbook.1 The visual exciter was moved to 144 MHz, In the visual transmitter, the last 6360 drives a surplusLink 450 MHz FM final

The other feature of this transmitter is the inclusion of an FM sound transmitter 4.5 MHz above the picture carrier. By sending audio along with video, the receiving station copies the entire signal directly on the TV set. Because of the narrow bandwidth of the audio channel, a power of only about 10 or 20 per cent of the visual power is needed, and the second 220 exciter drives an old surplus ARC 27 final to about 10 watts output/*

The video modulator used at K3ADS is a convertered commercial unit and due to the ina vail ability of many of the parts, I will not

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