A small hack on a commercial CATV TV demodulator.  An Olson Technology OTD-3000 TV demodulator is modified to run from a 12-volt battery and the PLL sythesizer was replaced with a manual tuning potentiometer.  This allows for quickly scanning the airwaves (or coaxial cable line) for any NTSC TV transmissions.  This is very useful for TSCM applications or for receiving video from your own TV transmitter.

Block Diagram

Pictures

• TV Demodulator - Picture 1  Case overview.  Rack mount case was replaced with an ammo box.
• TV Demodulator - Picture 2  Front panel view.  The large knob is the tuning pot, the three BNCs on the right are for RF input, divide-by-64 prescaler output, and video output.  The three switches select which band (VHF-low/VHF-mid/UHF) the tuner covers.
• TV Demodulator - Picture 3  Internal view.  It's not finished in these pictures.  The large black Astec 12-to-36 volt DC-DC converter is shown.  By using 36-volts for the voltage tune, the tuner will cover slightly more bandwidth, but is not needed.
• TV Demodulator - Picture 4  Demodulator board.  The yellow line (with red heatshrink) is the voltage tune line, replacing the line from the PLL loop filter.  The F connectors where removed to fit the board in the ammo box.  Coax was then used to bring the needed lines out to the front panel BNC connectors.  You can also see the bottom control lines (dipswitch removed) for band select).
• TV Demodulator - Picture 5  Behind the front panel.
• 45 MHz IF Display - Picture 1  This is a quick hack on an old portable B&W TV.  A 45 MHz IF input jack is added where the tuner's IF output used to go.  This allows the monitor to directly display 45.75 MHz IF signals from the OTD-3000 or other CATV modulators.
• 45 MHz IF Display - Picture 2  Internal closeup.  The portable TV is surrounded by sponges to absorb any shocks.

Notes

• Olson Technology OTD-3000 TV Demodulator Datasheet  (667k PDF)  Contains technical specifications and dipswitch tuning information.