Florida Repeater Council
The Plus of PL
In Shakespeares day, "to be or not to be" was the burning question. Times have changed. Technology has complicated our lives. It is not merely enough "to be", at least if you are an Amateur Radio repeater in Florida. The question that now consumes repeater owners and users is, "To tone or not to tone?"
Private Line (PL) or Continuous Tone Coded Squelch System (CTCSS) tones have been around for a long time. They are widely used in other radio services, including the substantially more crowded Commercial Land-Mobile Service, the General Mobile Radio service (GMRS), and even the Family Radio Service (FRS). Their purpose is to keep users of Repeater A from accessing Repeater B, Repeater C and any other repeaters that may be operating on the same frequency, and often in the same locale or metropolitan area. At the same time, Land-Mobile and GMRS repeaters often transmit a PL or CTCSS tone to allow users to selectively filter out all other repeaters transmitting in a locale on the same frequency. And even though repeaters are not used in the Family Radio Service, many FRS radios use PL tone squelch to maintain some privacy to their conversations.
Amateur Radio repeater owners have been slow to adopt PL/CTCSS for a variety of reasons. In some cases, repeaters are owned by clubs comprised of a mix of new hams with modern, up-to-date equipment, those who have been around the block for a while, and whose equipment reflects a simpler time. Those owners of less-modern equipment sometimes adamantly refuse to embrace change. In other cases, the repeater owner/trustee simply does not see the real need to add PL encode/decode to the repeater.
But this is Florida, "Land of the TropoDuct" where transmissions that should be line of sight often extend far beyond the horizon and propagate hundreds of miles. With nearly forty thousand licensed hams in the Sunshine State, the need for repeaters continues to grow. This means fewer and fewer so called "clear frequencies".
In fact, the Amateur Radio two-meter and seventy-centimeter bands are teaming with repeaters. It is not uncommon to find five or more repeaters using the same frequency pair. While the Florida Repeater Council (FRC), the authorized repeater coordinating body in the Sunshine State requires a minimum distance separation of eight-five (85) miles between repeaters using the same frequency pair, this, often times, is not enough. A single user may find himself accessing two or more repeaters operating on the same frequency, unless those machines require a PL tone to access the repeater receiver.
Now, if that single user can access multiple repeaters, those repeaters will now compete for airspace, creating an annoying heterodyne or squeal in the process. Ouch! Try communicating a cogent thought to someone over that. Its not easy. To solve this problem, and help those operators who wish to selectively listen to their local repeater (as in singular), some owners add a PL tone to the repeater output, or allow the users PL tone to pass through. Such use of PL can also minimize the reception of disruptive intermodulation signals in metropolitan areas.
As the Florida sandbar keeps shrinking, and the pressure for more Amateur Radio repeaters continues to grow, the need for PL encoding and decoding will become imperative, if good engineering and operating practices are to be employed. Even those repeaters located in the middle of nowhere will need to add PL/CTCSS toning to keep the greater RF neighborhood a friendly place to "play radio". By the way, if someone can tell me which county nowhere is located in, I would like to visit it someday!
Written by Paul J. Toth NA4AR
Latest update: 10 February 2002