GatesAir eliminates interference between two California FM stations

GatesAir supplies Intraplex IP networking solution

GatesAir has supplied an Intraplex® intelligent IP networking and synchronization solution to KCSN (FM) for resilient signal transport across its new single-frequency network (SFN).


Broadcasting on 88.5 MHz from the campus of California State University in Northridge, KCSN has long struggled with mutual interference with another FM station, KSBR, broadcasting on the same frequency from Saddleback College in Orange County. The transition to an SFN with Intraplex IP networking brought the two stations together into a unified operation, solving the problem of interference as listeners traveled through the Los Angeles area.


“While KCSN has a clear signal in the northern metro area, it would turn into a horrible mishmash of two signals as drivers traveled south toward Orange County,” said Michael Worrall, technical director and chief engineer, KCSN.


“The same happened for KSBR listeners as they drove north. The only solution was to join forces with a common format, and have the same program broadcasting from all transmitters. We wanted to utilize the best, state-of-the-art products to help overcome the obstacles that have historically hindered SFNs, so we consulted with some of the best minds in the business at GatesAir and elsewhere to find the right technical solution.”


The complete system brings three transmitters together using an Intraplex IP Link MPXp codec

Those consultations steered KCSN toward an SFN architecture that provided a seamless transition between transmitters as people travelled through the region. The complete system brings three transmitters—KSBR, KCSN main and a KCSN booster in Beverly Hills—together using an Intraplex IP Link MPXp codec with integrated Intraplex SynchroCast® technology to simulcast and time-lock the signals. This technique ensures that the three overlapping transmitters operating on the same frequency, and avoid interference with each other while broadening overall signal coverage.


Worrall migrated from a T1 architecture to IP based on several new efficiencies that the IP Link MPXp brought to the surface, including lower monthly costs, reduced capital investment, and support for a transparent AES192 digital multiplex composite signal. A competitive analysis of MPX codecs on the market proved that the GatesAir solution excelled in dual-domain design, network reliability and built-in dynamic SFN capability. The migration from T1 to IP has also saved the operation about $1700 each month, which uses a very wide-bandwidth, private Ethernet service from AT&T to accommodate all signal networking.


 “The MPXp allows us to originate the baseband signal at our Northridge studios, and duplicate that signal within the codec, maintaining strict control of signal levels and phase across the network,” said Worrall.


“We’re confident that the high-quality AES192 audio is being delivered to all three transmitters identically. It also gives us a simultaneous analog MPX composite output to route program audio to our backup transmitters, which aren’t yet capable of accepting an AES192 digital stream. We can do this all from one codec, and without the burden of adjusting audio levels in T1 frames to match modulation levels. The MPXp keeps those modulation levels identical, which eliminates the noise floor for the cleanest signal for our listeners. And we’re doing this all for about $330 per month – compared to $2,000 a month had we remained on T1 – without sacrificing any reliability associated with signal transport.”


“GatesAir has long been at the forefront of innovation in intelligent networking to problem-solve interference and coverage shortcomings in over-the-air broadcasting,” said Bruce D. Swail, CEO, GatesAir. “Our Intraplex solutions are providing the best of both worlds for KCSN by providing a far more robust signal over greater distances, and simultaneously saving our customer thousands of dollars annually.”

TM Broadcast International

Broadcast and audiovisual digital magazine