KTVN Silver Springs DTV Translator K29BN D in KTVN Shop
The Harris/Gates Air UAX 100 translator has passed the weekly on air at full power into the dummy load and is ready to be transported to the site at Eagle Ridge and be installed. Power 125 W Ch 29 Pilot 560.31 MHz DM 101 Demodulator is mounted under the keyboard drawer
The UAX 100AT Proof of Performance was done by Harris in Quincy, Ill. The test patterns are shown here. The skirts are quite good at 60 db The EVM of 2.0 % is higher than our 20 KW Platinum at 1.4 % but very good. Error Vector Management The UAX 100 AT Signal to Noise of 33.8 db compared to the Platinum at 38.3 db.
UAX 100 AT Eye pattern Harris 20 KW Platinum Solid State on Slide Mountain.
The Mask filter of the Harris Platinum on Slide
The control of the UAX 100 AT can be done from the GUI which is really helpful for trouble shooting.
The operation with the Workstation running XP will also show what the HD images look like.
The GUI will also show the Spectrum in a window to let you know how flat the signal is and what the power level is using the Dell XP PC behind the flat screen.
The Scala Antenna is cemented into a pile of rocks on Eagle Ridge and has been in the same spot for over ten years. We added another panel to gain more coverage in Fernley, Nevada.
The Surge Suppressor is the Transtector from Idaho. The Gallium Arsenide protection is the fastest switch to ground and has protected the UAX 100AT from the high Surges from NVEnergy.
RF Pattern that would benefit KTVN the most from K29BN D
Viewers in Fernley, Silver Springs and Yerington can see KTVN CBS 2.1 and AntennaTV 2.2 with Surround Sound on CBS and Stereo on AntennaTV. The SAP channel of 2.1 has CBS audio in English and Spanish for the Soap Opera and Football games. The GPS location of the antenna on Eagle Ridge.
The ATSC Transport Stream that is transmitted from the KTVN Harris SS Transmitter on Slide is an MPEG 2 SMPTE 310 that has PIDs for each of the elements. Tektronix MTM 400 Transport Stream Analyzer of KTVN 2.1 & 2.1
The input signal to our DTV transmitter is a synchronous serial interface (SSI) 19.39265846 Mbits/Sec binary data stream in a SMPTE 310M format. KTVN 2.1 is 13 MBps and 2.2 is 3 MBps the other six MBps is from the Selenio Encoder, The NetVx Back up encoder will use more bandwidth for 2.1 so for failover we need the compression settings for the NetVx Encoder with the older Compression Algorithms. The Harris Apex DTV I/Q Modulator accepts the 8 level data and modulates it onto an IF carrier. Our conceptual phasing method I/Q modulator suppresses the lower sideband and carrier. A DC component creates a phase imbalance in the modulator to produce a 0.3 db pilot carrier leakage (about 7%), which aids in recovery of the modulation at the receiver. The resulting frequency spectrum, usually centered on an intermediate frequency of 44 MHz, is heavily band pass filtered to limit most of the energy to a six MHz channel bandwidth, which by Nyquist theorem can convey the 10.76 symbol/sec signal with a modest overhead. This IF signal is then up converted to the desired television channel 210.7 for KTVN DTV Channel 13 for amplification and final clean up band pass (FCC mask) filtering as it leaves the building for the antenna.
KTVN DTV Channel 13 Harris Platinum Transmitter with Dielectric Mask Filter.
The generic name for this modulation scheme is 8VSB; 8 for the eight amplitude levels modulated on the RF carrier, and VSB for the presence of the vestigial side band carrier and rapid roll off of frequencies below the carrier frequency. DTV power can be measured by integrating energy across the 6 MHz channel using the FFT Spectrum approach shown in the Mask Filter photo of the Tektronix RFA 300 Spectrum Monitor. For the Constellation image in the Tektronix RFA 300 we are looking at the on air DTV signal with a single sweep oscilloscope, voltage vs. time, we would see an amplitude modulated RF envelope. Since the modulating data is pseudo random, the display would fill to flat amplitude over successive sweeps of the oscilloscope. By recovering a clock from this RF signal, using a Tektronix RFA 300, we can sample the signal to discover the closest of eight possible levels occurring at the time of each sample. Each level represents a three bit binary word that contributes its pattern of three bits to the recovered ATSC baseband data stream.
The ability for the receiver to faithfully recover the correct 3 bit symbol is aided first by the transmitted pilot signal. It is then up to the demodulator to evaluate the instantaneous amplitude level of the signal to estimate which of eight possible modulation levels is the correct symbol to report as a 3 bit word. Once the signal is successfully sampled, additional locking and correction can take place to recover the Data Segment and Data Field Syncs. Then error correction and data decoding can begin. Harris has chosen the Z Technology DM 101 to demodulate the KTVN DTV Channel 13 RF signal and produce the Transport Stream to enter the UAX 100 AT Translator which will output DTV Channel 29. Inter symbol interference resulting from the severe band limiting of the data is avoided by using level information gathered only during the sampling time. At the instant of sampling, ringing from previous and subsequent symbol levels will be at a zero crossing and only one symbol will contribute to the RF envelope. This is illustrated by the measurement demodulator eye diagram display shown in the RFA 300 and in the GUI of the UAX 100 AT.
The Eye wants to be open and with Adaptive Correction on it will start closed and take several minutes to open like the RFA 300 image above and the Harris Apex DTV Exciter.
The Harris ATSC Test Equipment rack at the Slide Mountain DTV Transmitter site with the Tektronix RFA 300 and Transport Stream Analyzer is used to measure the Apex and CD 1 HD Exciters. Successful transmission of the DTV signal, requires a properly adjusted exciter/modulator, an RF amplifier chain that exhibits very linear performance, and proper filtering at the transmitter output to minimize radiation of out of band components.
What is 8VSB 8VSB is an 8 level vestigial sideband modulation. In essence, it converts a binary stream into an octal representation by amplitude modulating a sinusoidal carrier to one of eight levels. 8VSB is capable of transmitting three bits (2 3 =8) per symbol; in ATSC, each symbol includes two bits from the MPEG transport stream which are trellis modulated to produce a three bit figure. The resulting signal is then band pass filtered with a Nyquist filter to remove redundancies in the side lobes, and then shifted up to the broadcast frequency. [1] The definition of 8VSB says: does not fully exist when the RF signal is transmitted, but rather only after it is filtered for a second time in the receiver.
EFFECT OF NYQUIST FILTER ON 8 VSB IF ENVELOPE EFFECT OF NYQUIST FILTER ON 8 VSB IF ENVELOPE Top: Double sideband IF envelope before Nyquist filtering. Bottom: The same IF signal after Nyquist filtering. The squared off transitions are lost and the envelope acquires a noise like appearance.
A subtle clarification: The 8 VSB system actually employs a matched pair of Nyquist filters one in the exciter (to reduce transmitted bandwidth), another in the receiver (to eliminate adjacent channel interference). Each Nyquist filter provides one half of the orthogonal impulse response described above. The effect shown in the next figure, therefore, does not fully exist when the RF signal is transmitted, but rather only after it is filtered for a second time in the receiver.
Thank You Have a good day, Alan Alan Nichols Chief Engineer KTVN Channel 2 News CBS 4925 Energy Way, Reno, NV 89502 Main: (775) 861 4276 Cell: (775) 762 5233 anichols@ktvn.com