Based on the very successful Scientel TV Power Monitor (TVPM) design, the TV Demodulator (TVOA) can operate as a studio monitoring demodulator, as a re-broadcasting receiver or as a signal-level monitor.
Benefits
The TVOA’s wide bandwidth allows coverage of the whole VHF and UHF Television range with a single unit. Its excellent low-level sensitivity and extremely low input return loss ensure optimum performance in fringe signal zones while the highly linear response makes it the ideal receiver for rebroadcast applications.
Technical Information
The TVOA has a wideband (54-810 MHz, channel 2 to 69) 50Ω input. It requires a 6MHz channel band-pass filter at its input when connected to an antenna or CATV source. The band-pass filter and a double-shielded matched cable to connect the filter to the TVOA are provided. The channel number is specified at the time of order by adding a -xx suffix to the TVOA product code (xx=channel number).
The sensitivity of the TVOA is increased from the standard –16 dBm of the TVPM to better than ‑42 dBm.
The VSWR at the input of the system is less than 1.2:1 (>21dB Return-Loss) on any VHF/UHF channel. The gain adjustment range totals 21 dB of which 15 dB comes from the RF attenuator (1 dB steps) and 6 dB comes from the IF variable attenuator. If the signal level from the antenna exceeds –20 dBm, an external series attenuator can be used. For 75-Ω antenna systems, a 75 to 50-Ω matching transformer must be used, but in cases where the received signal exceeds ‑20 dBm, the matching transformer can be replaced with a matching pad.
The power monitor section of the TVOA is identical to the TVPM. Remote monitoring of the receive signal level is possible by connecting the unit to a Davicom MAC remote monitoring & control system.
Visual demodulator is of the synchronous, high performance type and allows evaluation of amplitude versus frequency and transient responses of the transmitted visual signal as well as differential gain and phase of the colour sub-carrier.
On site, visual percentage of demodulation can be measured with the built-in zero carrier reference pulse inserted in the video’s vertical interval. A bar graph peak level meter is also available for the measurement of the audio percentage of modulation.
The audio and video outputs from the monitor can be used to feed audio and video presence detectors such as the Scientel
Dual Audio Presence Detector (DAPD) and
Dual Video Presence Detector (DVPD). These units generate a DC voltage proportional to the peak level of the audio and video signals and give alarm indications if the audio or video levels drop below user-programmable thresholds. These signal levels and alarms can be connected to a Davicom MAC unit for remote monitoring.
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ELECTRICAL SPECIFICATIONS |
| Power Requirements |
+12 VDC Regulated, 300 mA
-12 VDC Regulated, 250 mA
+5 VDC Regulated, 300 mA |
| Input Attenuator |
1 dB, 2 dB, 4 dB, 8 dB. Total 15 dB on
Front Panel |
| Input Impedance |
50 Ω |
| Frequency Range |
54-810 MHz (TV Channels 2 to 69) |
| Input VSWR |
< 1.2 : 1 over the whole frequency range |
| Input Sensitivity |
-42 dBm ± 3 dB with RF Attenuator Out and IF Attenuator to Maximum Level |
| IF Level Range |
6 dB Adjustable from Front Panel |
| Gain Adjustment Range |
21 dB (15 dB RF, 6 dB IF) |
| Frequency Programming |
16 DIP Switches on Front Panel |
| RSSI |
-42 to -20 dBm |
| Audio Output (mono) |
Adjustable from Front Panel, 0 to 10 dBm,
600 Ω Balanced |
| Audio Muting |
ON when Transmitter Power drops by more
than 20 dB |
| Audio Distortion |
Less than 0.9% |
| De-Emphasis |
75 µs Standard 50 Hz to 15 kHz |
| Audio % Modulation Indicator |
LED Bar Graph (7 Green, 3 Red) |
| DC Output |
0 to 7.5 VDC Linear, set at 5 VDC for
Normal Transmitter Power |
| Alarm Contacts Out |
SPDT Adjustable Comparator to Signal and
Alarm at the desired Transmitter Power Level |
| Video Output |
1 V peak-to-peak (140 IEEE units*) |
| Video % Modulation Indicator |
Keying Pulse in Vertical Interval |
| Video Frequency Response |
±0.5 dB from 0.2 MHz to 4.0 MHz,
3 dB down at 4.1 MHz |
| Video "K" Rating |
1% for 2T Pulse |
| Group Delay |
±20 ns, .2 to 4.1 MHz |
| Differential Gain |
1% maximum |
| Differential-Phase |
1 degree maximum |
*IEEE units = IRE
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MECHANICAL SPECIFICATIONS |
|
Operating Temperature |
+32°F to 122°F
0°C to +50°C |
|
Dimensions |
1 5/8 x 8 1/2 x 12 in (H x W x D)
4.1 x 10.8 x 30.5 cm |
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Input Connector |
BNC Female |
|
Audio Outputs |
Front Panel Audio 3 Way Jacks and
Rear Connectors |
|
Rear Output Connector |
Weidmuller Terminal Block |
|
Video Output |
BNC Connector on Front Panel and Rear Panel |
Product ordering code: TVOA-xx
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