Belar: "When accuracy counts, count on Belar"


TVM-230 photo


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.

TVM-230 drawing


Inputs 				Two wide-band demodulated aural
   				composite, selectable from front panel

Input Level 			1.0V to 2.0 Vrms for 
				73 kHz peak deviation

Input Impedance			100 kW, unbalanced
   				BNC connector


   Left and Right

       Audio 			Active 50 W Balanced Output
   				Level: +10 dBm into 600W, 
				XLR connector

       Test			2.5 Vrms, 75 W, unbalanced,
   				BNC connectors

       Scope (auto-ranged) 	1.3 Vrms, 75 W,
   				unbalanced, BNC connectors

   Pilot Output 		2V P-P, 500 W, unbalanced
   				BNC connector

   dbx Level 			3.536 Vrms for 50 kHz L-R
   				deviation, BNC connector


   Serial Interface		RS-232, DB-9 connector

   Unit Interface 		Wizard Standard Interface

Remote Meter Outputs:
   For interface to optional Model MP-230 Analog Remote Meter

	Analog Meter Outputs for Left, Right, 
	   L+R and L-R channels

        Open Collector outputs for Stereo Peaks Per
   	   Minute (PPM), L+R PPM, Pilot

   Relay closures for Stereo PPM, L+R PPM, Pilot

Separation + Noise

   Equivalent Mode		70 dB, 50 Hz to 14 kHz

   BTSC				Exceeds EIA MTS recommended
   		practices for monitoring equipment. Typical
		separation at 100%, 75 µsecond equivalent 
		input modulation:
   		50 Hz to 8 kHz 		greater than 40 dB

   		8 kHz to 12 kHz		greater than 35 dB

		12 kHz to 14 kHz	greater than 30 db

Crosstalk + Noise

   L+R to L-R 			75 dB
   		     (50 Hz to 14 kHz)

   L-R to L+R 			75 dB
   		     (50 Hz to 14 kHz)

   SAP to L+R 			75 dB

   SAP to L-R 			75 dB

   PRO to L+R 			75 dB

   PRO to L-R 			75 dB

Frequency Response (Left and Right channels)
   Equivalent Mode 		± 0.05 db
   (50 Hz to 14 kHz)

   Typical at 100% 75 µsecond equivalent input 
   modulation			 within ±0.1 dB
   				(50 Hz to 14 kHz)

   Typical between 10% and 100% 75 µsecond equivalent
   input modulation:
   	50 Hz to 8 kHz 		within +0.05 to -0.02 dB
   	8 kHz to 14 kHz		within +0.05 to -0.35 dB

Signal-to-Noise Ratio
   (L, R equivalent mode, pilot on)
   No de-emphasis 			75 dB
   De-emphasized, 75 µsecond	85 dB

Distortion + Noise

   Harmonic Distortion:
   	(50 Hz to 14 kHz, measured across 30 kHz bandwidth)
   	Equivalent Mode		 0.025%
   	BTSC			 0.1% 

Signal Input-to-Output Delay 5 milliseconds

Dimensions 		1 EIA Rack Unit
			1.75"H x 17"D x 19"W

Power Requirements     30 watts, 100-240 VAC
			  50 to 60 Hz

Shipping Weight        13 lbs

© Copyright 2000 Belar Electronics Laboratory, Inc. All rights reserved. Specifications subject to change without prior notice.

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