Transcom
 
 
 
 
 
 
 
 
 

 

Techanlogix TM150 Modulator

The high output modulator eliminates the need for preamplifiers prior to the power amplifier system. The modulator processes baseband audio and video information to provide an IF output consisting of a visual IF carrier at 45.75 MHz, using amplitude modulation, and an aural IF carrier at 41.25 MHz, using frequency modulation. An internal upconverter translates the modulator circuitry's IF carriers to VHF and UHF television frequencies. All operating controls are located on the front panel. An aural loop through is provided to properly set transmitter power.

 Standard Features:

  • Selectable output channels:

         Standard Broadcast VHF, UHF,

  • SAW filtered IF designed for adjacent channel operation
  • + 60 dBmV output using low distortion hybrid amplifiers
  • Synthesized oscillators - crystal referenced phase locked
  • Modulation LED readout
  • Surface mount technology construction
  • Phase lock loop FM audio
  • BTSC stereo compatible
  • External separate audio/video and composite IF loop-through
  • Aural carrier level adjustable -10 dB to - 15 dB
  • Video delay predistortion network meets FCC 73.687
  • High stability TCXO, + 250 Hz
  • Non-volatile memory retains channel selection after power loss

 

RF Characteristics

Frequency Range

7 to 750 MHz

Frequency Response (one Channel)

0.5 dB

Frequency Stability

250 Hz

RF Output Level

60 dBmV max

Harmonics

>60 dB below rated power

Predominant Intermodulation Products

dBc = decibels below visual carrier

+920kHz

>60 dBc

-920kHz

>60 dBc

+2.66 MHz

>60 dBc

-2.66 MHz

>60 dBc

+5.42 MHz

>60 dBc

+7.16 MHz

>60 dBc

3rd Order Intermodulation Products

 

-4.5 MHz

>60 dBc

+9.0 MHz

>60 dBc

All Others

>60 dBc

Spurious Emissions

>-60 dBc

NTSC Video Characteristics

Input Level (for 87.5% modulation)

1.0   Vpp

Differential Phase (at 87.5% modulation)

2 Degrees

Differential Gain (at 87.5% modulation)

2 %

Group Delay

< 40 ns

K-Factor

1.9% for 2T Pulse

Hum and Noise

> 60 dB below rated Power

 

Aural Characteristics

Input: 50 Hz – 15 KHz

0 dBm (0.8V)

Impedance

600 ohms, balanced

Frequency Response

1 dB

Frequency Tolerance,  500 Hz

4.5 MHz

Frequency Deviation

25 KHz

Harmonic Distortion

1% max

Preemphasis (mono) Internally Defeatable

75ms

  

IF Section

Output Impedance

75 ohms, unbalanced

Video IF level

+ 37 dBmV, +97 dBmV

Audio IF level

+ 22 dBmV, +82 dBmV

Return Loss

>14 dB

Video Sound Spacing

+ 4.5 MHz

Vestigial side-band width

0.05 MHz

Second IF Frequency

945.75 MHz