The Belar TVM-230 is a digital BTSC TV Stereo Monitor/Analyzer. Operated in conjunction with the Belar TVM-100, TVM-101, or other wideband aural demodulator, the Belar TVM-230 provides the measurement capability necessary for the set-up, test, and measurement of BTSC Stereo TV transmission systems, as well as providing accurately decoded Left and Right channel audio outputs.
The TVM-230 digitizes the complete demodulated aural signal and decodes the stereo multiplex portion using digital-signal-processing techniques. Unlike analog designs, this DSP-based design is immune to variations due to temperature or the aging and tolerance of components. By employing linear-phase FIR filters, the TVM-230 reduces phase distortion in the recovered audio, providing unprecedented accuracy in measuring modulation peaks of the Left, Right, L+R, and L-R signals. Accurate decoding of the encoded BTSC is assured by the on-board professional dbx expander card.
The TVM-230 combines all its functions in a single chassis only one rack unit high. Two large seven-segment LED displays simultaneously indicate peak modulation percentages of the Left and Right channels. Two LED's indicate when modulation "Peaks-Per-Minute" counts for the Stereo and L+R channels have exceeded preset limits. Two other LED's indicate the presence of the stereo pilot and operation of the monitor in "Test Mode".
Readings of the Left, Right, L+R, L-R signals, along with Total, are provided both as peak percentages and relative decibel (dB) indications. The internal auto-ranging RMS voltmeter allows direct readings to be made of Separation, Crosstalk, and Subcarrier Suppression in dB. The TVM-230 also indicates peak level of the Stereo Composite signal and pilot injection. Rear panel outputs include relay closures for the front-panel alarms, and analog signals to drive the optional stereo remote meter panel. Installation of Option 01 provides indications of when the stereo pilot is synchronized with the station's horizontal sync (applied to rear-panel video feed-throughs).
All operational and metering functions of the TVM-230 can be controlled via the front-panel menu system. One pair of UP/DOWN keys provides menu control, another pair of keys adjusts operating parameters. Settings under menu control include peak flasher parameters, L-R channel companding, and selection between the two monitor inputs.The Belar TVM-230 BTSC TV Stereo Monitor provides an RS-232 port, permitting full operation and readout under computer control. With the addition of a 2400-bps modem and the supplied Wizard software the unit may be controlled, via a standard telephone line, from any off-site location. The TVM-230 may also be used in conjunction with other Belar monitors via the Wizard interface. The Wizard system turns an ordinary PC into a powerful tool for the display and logging of BTSC TV Stereo modulation parameters