Ed Murlatt & Associates, Inc.
RF Services for the Broadcast Industry
Basic SFN Planning Considerations
A Single Frequency Network (SFN), may be the answer to filling one or more holes in a station's DTV coverage area.  Falling under the broader category of Distributed Transmission Service (DTS), it may be easier to get approval for an SFN, since unlike a translator, all the transmitters in an SFN are on the same channel as the primary channel.  The multiple boosters must still comply with interference rules, and there are coverage limits.  The various rules are beyond the scope of this discussion, and can be better addressed by your FCC consultant.

In the early planning stages, coverage and interference studies will be conducted to determine the appropriate location, antenna pattern and ERP for the booster site(s).  These studies will show where coverage will improve, and show where the two transmitter may present inteference to each other.  In addition to being a part of the application process, you will also need to know some booster specifics for budgetary purposes and feasibility analysis. 

Here is a simplified shopping list for a one booster SFN:

Due to large number of configuration variables, the list above is simplified into the basic building blocks required for a simple SFN,  A couple of notes - If you change the main transmitter's exciter, you will need to do a proof of performance.  Whether microwave, fiber or some other link is employed to the main transmitter and/or booster site, be certain the transport stream remains unchanged.  The streams fed to all exciters in the SFN must be identical. 

Prior to bringing the SFN online, studies will be conducted to determine appropriate locations for monitoring timing.  It is important both transmitters can be received and the relative timing is similar to that of the desired coverage area.  It is also desirable to have a location where both signals are approximately the same strength.  In addition to locating ideal timing locations, it is also important to identify test sites to evaluate reception where interference is predicted, as well as several locations at the extremes of the coverage area.    Coming soon SFN Implementation
» In the meantime, here's a little more SFN information in an article about an operational SFN.      
Remultiplexer to insert ATSC M/H Sync Information
Main Transmitter Exciter Capable of Passing M/H Sync and SFN Timing
Booster Transmitter
STL to Deliver the Transport Stream to the Booster
Tower Site Lease (or Purchase) for Booster
Booster Transmission Line
Booster Antenna
Remote Control Capability for the Booster
GPS Receivers to Provide 10 MHz and 1 PPS Signals to the remultiplexer, and the Main and Booster Exciters