Mobile 8-VSB?
Apr 1, 2003 12:00 PM, Brad Dick editorial director
Broadcast Engineering was recently privy to a series of secret tests on the latest improvements to 8-VSB chips for mobile reception. These new chips have been specifically designed to improve the capture and display of 8-VSB signals in mobile environments. Let's look at just a couple of the test results. (Glossary of terms below.)
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The first mobile reception test was designed to measure the Barrington Angular Reception Factor (BARF) constant. A human reception model, shown here, was used to avoid any metal reflections from the automobile. The subject engineer was loaded with about 42 pounds of electronics and wore a head-mounted antenna to minimize body shielding. This was required to minimize the constant Zenith BARF noise.
The test subject then walked a 16:9 grid pattern and at each crosspoint a series of tests were conducted and results logged. The images were displayed on a new portable TV set displaying FFHD images.
The first video test focused on measuring the Circular Radiation and Polarization (CRAP) factor. This analysis looks at how effective reception is when the person or vehicle is moving in a clockwise direction. The same test is useful when the receiver moves counterclockwise, but that wasn't measured in these tests. The results were as expected. On the CRAP scale of 1 to 10, the new ATSC improvements rated a strong 10.
Unfortunately, the electric component of the magnetic sinusoidal waveform was often absent. This meant that the CRADT measurement went off the scale. At these locations, the engineer was instructed to apply first the HYB correction mode for 30 seconds. If that didn't improve the reception, the HAP correction mode was applied for 60 seconds. Unfortunately, these corrections seldom worked. These test locations were identified on the test grid as CRADT 1 through 22.
Because of the high number of CRADT results, a second round of tests was conducted. These tests were restructured to just measure CEGADS, sometimes called “C-GADS.” Researchers felt that this was probably going to be a bottom-line performance measurement anyway, so identifying it early might prove beneficial.
Test results, while encouraging in flat-plain environments like parking lots, were less so anywhere near a building, tree, light pole or moving dog. Also, as the subject walked clockwise around the grid, the FFHD image was visible, but it also rotated clockwise. The only way the image could be stabilized was by walking counterclockwise around the grid. Finally, if the test subject passed near any building or car, the CRAP hit the fan and even FFHD was unviewable.
We are awaiting a new round of tests to be conducted just after the NAB convention.
Glossary:
Barrington Angular Reception Factor (BARF)
Fox-Fake HD (480 line) (FFHD)
Circular Radiation Angular Polarization (CRAP)
Can't Receive A Damn Thing (CRADT)
Hold Your Breath (HYB)
Hope And Pray (HAP)
Can't Even Get A Digital Signal (CEGADS)
I hope readers enjoyed my April Fool's story.
Send comments to: • editor@primediabusiness.com • www.broadcastengineering.com
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