Günter MarksteinerMIAMI/STUART, FLA.
I own and operate several independent TV stations in Massachusetts and Florida. These include a full power digital television facility in Stuart, Fla. and a low power digital station located in Miami.
Since the initiation of regular service, the various solid-state, tetrode and IOT-based DTV transmitters used at these stations have employed pre-correcting ATSC 8-VSB modulators supplied by KTech Telecommunications. The modulator at WHDT Miami was recently upgraded to a KTech Xtreme-1000E 8-VSB modulator/translator to benefit from its fully integrated high performance digital television receiver.
SIGNAL RETRANSMISSION
The Channel 44 low power outlet in Miami retransmits high-definition programming throughout the Miami-Fort Lauderdale market received off-air from Channel 42 in Stuart. (The full power Stuart station serves the West Palm Beach DMA and is located 57 miles north of Miami.)
The main transmitter for the Miami operation employs a 25 kW water-cooled tetrode transmitter equipped with a solid-state IPA, both manufactured by Thales, and operates from a 1,000-foot tower in North Miami. That station's log-periodic off-air receiving antenna, transmitter, mask filter, and transmitting antenna are located only meters from each other in order to permit efficient translation of DTV Channel 42 to DTV Channel 44.
KTech's Xtreme-1000E modulator system receives, equalizes and remodulates the distant off-air signal from the West Palm Beach station, updates incoming PSIP data, remaps the major channel and then applies both linear and nonlinear pre-correction to the 8-VSB signal being transmitted to the Miami-Fort Lauderdale market. An RF sample taken after the transmitter's DTV mask filter from a calibrated directional coupler provides power, signal quality monitoring and feedback control for the modulator. A mechanical contact closure generated by the modulator can automatically initiate a controlled shutdown of the Miami transmitter in the event of loss of a valid incoming data stream from the Stuart television signal being received.
Off-air signal quality for the Miami station is automatically logged and monitored in that station's master control room facility. Video signal quality is also monitored in West Palm Beach with a KTech DVM-150E DTV receiver connected to a log-periodic antenna.
MODULATOR DELIVERS HIGH QUALITY SIGNALS
The upgraded KTech modulator/exciter at the Miami transmitter facility has permitted the station to deliver a high quality and stable digital television signal throughout the entire DMA. In its latest firmware generation, the KTech Xtreme-1000E modulator exhibits nearly flawless 8-VSB technical parameters and maintains a tightly grouped and stable eye pattern after the pre-correction cycle. Startup calibration conveniently takes place a couple of dB below maximum transmitter power, and independent thresholds can now be set to reinitiate linear and nonlinear correction as needed while maintaining normal broadcast operation.
Günter Marksteiner, PhD, is an experimental physicist, and is licensee and chief engineer of the MIG television station group. Dr. Marksteiner also pioneered progressive high-definition broadcasting in the United States. He may be contacted atmarksteiner@whdt.net.
For additional information, contact KTech Telecommications at 818-773-0333 or visitwww.ktechtelecom.com.
