Project to Cut Multipath Progresses - Radio World

Project to Cut Multipath Progresses

Omnia, stations to field-test FM stereo single-sideband suppressed carrier transmission
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Processing manufacturer Omnia Audio hopes to have stations field-test FM stereo single-sideband suppressed carrier transmission.

In a letter to the FCC (PDF) regarding experimental authority for the field testing, Omnia President and Founder Frank Foti says the agency has begun to grant such requests and updates the agency on the project.

SSBSC can improve FM stereo transmission by modifying the L–R stereo subcarrier signal, according to Foti. He believes the approach also would reduce multipath, better protect the baseband spectrum and be compatible with existing radio receivers.

“The intended goal of this effort is to reduce perceived multipath of the FM channel through a reduction of occupied bandwidth and sideband pairs of the modulated carrier,” Foti writes.

“There are multiple benefits for the broadcast signal, which I feel will be perceivable to the listener: A reduction in multipath induced distortion, additional protection to the spectrum used for RDS, SCA signals, and HD Radio content — thereby improving data robustness in the receiver.”

Should this method be adopted, according to Foti, there’s a potential for up to 4 dB improvement in signal-to-noise performance of a stereo receiver, if the receiver was designed to recognize only the 38 kHz SSBSC signal. Manufacturers informally have discussed creating an FM receiver that automatically could decode either method of FM stereo transmission, he adds.

The National Radio Systems Committee has convened a sub-group to look into the SSBSC transmission method.

Omnia has mapped out a field-testing plan to determine if the SSBSC method does reduce the perceptible effect of multipath. It wants to verify lab test results with occupied bandwidth observations and testing at stations to see if there is any change in adjacent channel performance. Omnia would oversee the field testing and said it will provide a report of its findings.

Related:
A Method to Improve Conventional FM Stereo

Foti to Detail Stereo Improvement Plan to NRSC

Omnia White Paper (PDF)

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