ARCC Policy on Access Control

May 2002

ARCC has been reviewing its policy on access control. Access control is a means by which received signals are in some way authenticated or validated, such as by the use of a subaudible tone (CTCSS, otherwise known as PL), a digital code (such as DCS or DPL), or DTMF (touch tones). A common use of access control is a PL decoder on a repeater receiver. Because access control mechanisms have the significant benefit of minimizing annoyance key-ups by filtering out extraneous input signals from interference sources or from users of distant co-channel repeaters, ARCC has always recommended PL or other means of access control for all repeater and auxiliary link receivers.

In recent years, many coordination councils have adopted "mandatory PL" policies, requiring all repeaters to utilize PL on their receivers. ARCC has been considering enacting a similar policy. This was discussed again at the most recent ARCC Executive Board Meeting.   A motion was made, seconded, and passed unanimously that requires that:

  1. All new coordinated operations will require a means of access control on the receiver which shall be used at all times.

  2. All modifications to existing coordinations that currently do not have a means of access control will require such access control be added as a condition to the approval of the modification.

  3. All repeater and auxiliary links that are currently coordinated for carrier squelch access must coordinate a means of access control within the next three years in order to maintain coordination.

It is a common misconception that repeaters that utilize PL or another means of access control are "closed" repeaters. This is not the case. A closed repeater is one which is intended to be used only by a select group of users, typically dues-paying members of the club that sponsors the repeater, or in some cases, close friends of the repeater owner. It is perfectly legal to restrict access to a repeater to only certain individuals (47 CFR 97.205(e)), and using a closed repeater without the permission of the trustee is a violation of "good amateur practice" and may result in FCC action as has happened in several cases over the last few years. Sometimes PL or another means of access control is used to discourage unauthorized users from using a closed repeater, but that does not mean that all repeaters that use a means of access control are closed. The converse is also true – Part 97 does not require that a closed repeater have a means of access control. "Closing" a repeater is a policy decision, not a technical implementation. The majority of all repeaters (71%) and auxiliary links (80%) coordinated by ARCC already use PL or another means of access control. In contrast, of all of the repeaters coordinated by ARCC, only 5% are closed.

Some argue that by utilizing a PL tone that users with older-vintage radios that either lack PL or are equipped with an encoder that can only generate one particular tone will be unable to use the repeater. At this point in time, more than twenty years since PL-capable amateur radios became the norm, this argument applies to a very small minority of the repeater user population. In addition, a PL encoder board can be added to virtually any radio, further diluting the validity of this argument.

In addition, many repeater controllers can be programmed such that a touch-tone (DTMF) command can be sent by a user of a PL-incapable radio to put the repeater into carrier squelch access mode for a limited duration in time to allow them to communicate. However, it is imperative that the repeater revert to its coordinated mode of access control automatically once activity has ended, for otherwise, the whole purpose of access control is defeated.

In many areas, repeater sponsors have standardized on a common PL tone. For example, in the Philadelphia metropolitan area, PL 3B (131.8 Hz) is very common. In northern New Jersey, PL 4A (141.3) is prevalent. Utilizing one of these "regional" PL tones has both pros and cons. On the upside, it makes operating local repeaters easier for the users if all repeaters in a given area have the same tone. The problem, however, is that with multiple repeaters in close proximity utilizing the same tone, intermodulation (frequently called "mixing" or "intermod") that involves a transmitter which encodes a PL tone that is the same as the effected receiver is programmed to decode results in that PL tone being decoded, thus defeating the purpose of using PL as a means of minimizing interference. As such, there is an argument to be made in having repeaters in close proximity use varied PL tones to avoid such a situation.

ARCC requires that a repeater not utilize the same PL tone as any other co-channel or adjacent-channel repeaters on record in order to minimize interference from distant repeaters’ users. In addition, ARCC may recommend (or sometimes require, depending on the specifics of the operation) that a new repeater in proximity to other repeaters use a PL tone that is not the same as any of the other nearby repeaters to minimize intermodulation-related problems. In all but the most extreme cases of intermod mixes, however, appropriate RF filtering techniques (filter cavities, isolators, etc.) can be used to eliminate mixes, so for those who wish to opt for a regionally-accepted PL tone for their operation, provided there are no other co-channel users of the PL tone in question, intermodulation problems can be resolved at the RF level rather than relying on PL as a means of hiding the problem.

ARCC asks that the holders of coordination for any repeater or auxiliary link coordinated for carrier squelch operation begin thinking about implementing a means of access control. The three-year timeframe for migrating all carrier squelch operations to some form of access control should give all affected parties more than adequate time to do so. We thank you for your cooperation.