{"id":4308,"date":"2011-12-27T20:14:07","date_gmt":"2011-12-28T00:14:07","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=4308"},"modified":"2023-04-29T12:26:40","modified_gmt":"2023-04-29T16:26:40","slug":"synchronized-fm-signals","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2011\/12\/synchronized-fm-signals\/","title":{"rendered":"Synchronized FM signals"},"content":{"rendered":"\n

How effective are they at filling in or expanding coverage for FM stations? \u00a0The answer is, it depends. \u00a0Most have heard of the quadcast around New York City on 107.1 MHz formed in 1996-98. \u00a0It was well documented in Radio World and several other publications as a clever way to overcome the suburban rimshot problem. \u00a0Four signals on 107.1 were synchronized using GPS timing data, then fed the same program material. \u00a0They were WYNY, Briarcliff Manor, NY; WWXY, Hampton Bays (Long Island), NY; WWYZ, Long Branch, NJ; and WWYY Belvidere, NJ. \u00a0These being four separate Class A FM stations, the 60 dBu contours did not overlap. \u00a0There was some mutual interference in some areas, but there were few if any reception negative zones where the signal strength is equal between stations.<\/p>\n\n\n\n

In early 2003, I was a part of the disassembly of the quadcast. \u00a0In the end, it is difficult to point to any one thing that leads to the breakup. \u00a0The station’s owners, Big City Radio, had filed for bankruptcy. \u00a0I am not sure if the company ever had the correct formula for marketing and sales, given the strong suburban, but weak and lacking building penetration in Manhattan signal. \u00a0The station initially had a country format, something that armchair quarterbacks said would not work in New York City. \u00a0After a few years, Big City changed the format to Rumba, a Spanish\/Caribbean music format, which did worse than Country. \u00a0The fact is, that it never lived up to expectations and the station was worth more separately than together. \u00a0Given the right circumstances, it could have worked.<\/p>\n\n\n\n

The other synchronized FM broadcasts are those where boosters are employed. \u00a0These are a good deal more difficult to configure because the booster signal is within the main station’s 60 dBu contour. \u00a0Often cases, where there is severe terrain shadowing or other limitations, a well-positioned booster that is in a population center can greatly improve the signal in those areas. \u00a0This was formerly the duty of an FM translator, however, those stations seem to be taking on a life of their own, without regard for the intent of the current FCC rules. \u00a0Boosters can also be called a single frequency repeaters or single frequency network (SFN)<\/a>.<\/p>\n\n\n\n

The disadvantages of an SFN are the aforementioned negative reception areas. \u00a0To the receiver, this will create a multipath or picket fencing situation, which is objectionable to most listeners. \u00a0The advantages are, of course, better coverage in key areas, spectrum efficiency, and the ability to create a network of common frequency systems. \u00a0Think of how easy it would be if all NPR stations were all on the same frequency, for example.<\/p>\n\n\n\n

The key to making a booster work is to synchronize several aspects of the RF and Audio signals:<\/p>\n\n\n\n