1984

the MICROBOX SG was introduced. It was a quite advanced test signal generator. Subcarriers was stabilized by the switching Phase-Locked Loop (PLL) unit, so colour bars on the TV-screen had always the right colours. By the end of the year it was equipped with a PAL coder and other logic circuitry for generating the full Bruch Sequence - a 4-field blanking sequence generated in PAL coders to ensure that burst phase is the same at the end of each vertical interval.

And finally the VHF/UHF modulator was designed - the whole unit was lightweight and measured 24x11x5cm. On my knowledge some of this successful Microbox SG are still in service.

FIG. 1
Circuit diagram - PAL/NTSC 4.43 coder.

FIG. 2
Circuit diagram of a Bruch Sequence generator. This was a part of digital section of MICROBOX SIGNAL GENERATOR

FIG. 3

Red lines are the SECAM subcarriers mask. The longer line is the ideal characteristic of an VCO. The slightly curved line is the real f/v characteristic of the VCO. The vertical line is in kHz (3400 to 5200), the horizontal one is in V (1.5 to 3.5)

FIG. 4

For a high quality subcarriers in SECAM coder there is important to generate them in the highly linear VCO. After some experiments we found that the above circuit was simple and had a linear f/v characteristic. But DC-current ... 54 mA at 5V !