IBOC AM Antenna Performance Tips Shared

IBOC AM Antenna Performance Tips Shared
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There are about 137 stations on the air with HD Radio now and three versions of digital radios: Kenwood, JVC and Panasonic.
Receivers due out soon will come from Jensen, Alpine, Sanyo, Visteon and Delphi, said Ibiquity’s Scott Stull in a preview of what’s to come with IBOC in the HD Radio Workshop on Wednesday.
Ibiquity expects HD Radios to be original equipment in the dash on some car models at this time next year.
Switching to technical issues important for engineers to know as they implement IBOC at their plants, Ron Rackley of du Treil, Lundin and Rackley and Ben Dawson of Hatfield and Dawson discussed AM antenna performance concerns.
They said antenna performance needs to be right to get IBOC on the air and to get a robust digital signal. Many of the AM directional arrays installed in the 1940s are still in use; those that have not been optimized in the past 10-15 years may not perform properly to transmit a digital signal, both presenters said.
Rackley said lots of AM stations that have put IBOC on the air so far didn’t look at their antenna systems before making the switch.
Calls his firm has taken include those from engineers at some stations who say, “We hear bacon frying and the PD told us to take it off the air. What do we do?”
Rackley said that sound, or hiss from digital to analog crosstalk can be eliminated or reduced through various methods.
In the future, Rackley would like to see a more integrated approach between transmission and antenna specs for IBOC. The transmission specs are detailed but the antenna system specs are not, he believes.
He would like to see transmitter manufacturers specifiy antenna load requirements.
Clear Channel Radio’s Jeff Littlejohn, John Warner, and Tom Cox discussed case studies for AMs that have converted to digital, and shared tips for achieving a robust digital signal.


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