Quote:
Originally Posted by inaxeon
That having been said I'm not sure what a broadcast grade monitor/receiver would be built from. Philips did make them (PM5560/PM5696) but never seen inside one.
|
This block schematic of the BBC RC1-511 gives some idea of the structure, although I think that it may have been intended for broadcast monitoring rather than broadcast relay purposes. One may glean the impression that it used a larger number of simpler ICs than was the case in domestic receiver practice, where fewer, more complex ICs were typically used. (I have yet to see a full schematic for this unit.)
I suspect that in performance terms, the emphasis in broadcast receivers would have been on producing low distortion video with flat frequency response right up to the transmitted maximum, and a flat (or otherwise appropriate) group delay curve. PLL fully synchronous demodulation might be used, or if quasi-synchronous, then with a relatively narrow bandwidth reference channel with Nyquist slope cancellation. On the sound side, either fully split or if QSS or intercarrier, with specific features to achieve SNR and signal-to-buzz ratios close to those achievable with split sound. Basic QSS comes out somewhere between regular intercarrier and split on that front.
To be fair, some late consumer TV receiver ICs addressed these issues. For example, Sanyo pursued Nyquist slope cancellation in the demodulator reference channel, some European IC makers used PLL demodulation (single or double reference) for QSS, to get it closer to split sound. With its mid-1990s MC44302 vision and sound IF/demodulator IC, which unusually used intercarrier for AM as well as FM sound, Motorola claimed that with the addition of a differential phase correction circuit, sound performance equalled that of a split sound receiver. So by then, it was probably possible to do close to professional broadcast quality with consumer type circuits.
Cheers,