Simplex Repeaters

A simplex repeater records incoming transmissions and retransmits them on the same frequency. This has the effect of doubling the time required to transmit a message, but while a traditional repeater typically costs thousands of dollars and might be semi-portable at best, a simplex repeater can be set up with a single handheld radio and operated from batteries. This makes it perfect for disaster response, home or campground use, and any place where radio range needs to be extended but the cost and complexity of a traditional repeater can’t be justified. Additionally, the unique ‘say again’ repeat-on-demand feature of the ADS-SR1 allows it to be operated in silent mode, repeating transmissions only when requested. This can be used to repeat a missed transmission or to check for missed calls, even hours or days after the last transmission was heard by the repeater.

There are two distinct classes of simplex repeater operation:
1. Normal Operations
2. Emergency Operations

Normal Operations

Normal operation of a simplex repeater need to be "other ham friendly". Since many other simplex users will probably feel as though your simplex repeater is an intruder, friendly "co-operation" is necessary. A few concerns must be realized in order for your simplex repeater to be a good co-channel user.

First, avoid the use of common simplex frequencies, like 146.520 MHz, the National Simplex Frequency. Many folks enjoy using straight simplex and unless you have a compelling reason, avoid using simplex calling frequencies.

Above 2 meters you should endeavor to avoid repeater link frequencies as well. These frequencies can vary from region to region so it would be best to contact your local repeater coordinator to see if that particular frequency is being used.

Second, use a CTCSS (PL) tone to enable the receiver. This allows other users to use the simplex frequency without keying up your simplex repeater. If someone wishes to use the simplex repeater, then they must enable the proper CTCSS tone on their transmitter. If your simplex repeater also encodes the CTCSS tone (which is usually the case in most transceivers if decode is enabled) then it allows for selective monitoring of the frequency by those only wishing to hear users of the simplex repeater.

Third, ID the repeater and identify the CTCSS tone so that someone can communicate with you if you are interfering with their communications. Since another user probably won't want to try all the CTCSS tones to tell you that yourare interfering with them, be friendly and announce it over the air. IDing can be a user simply saying, " This is the N1NTE simplex repeater, PL 100.0 Hz".

And finally, use the minimum amount of output power necessary to maintain communications. While this is common sense and conforms to Part 97 rules and regulations, it is sometimes overlooked as a way to maintain good co-channel relations.

Remember, some users think that simplex repeaters have no place on simplex frequencies. At least be courteous to other users if you intend to use one.

Emergency Operations

Simplex repeaters and emergency operations seem to be a natural pair. Since a simplex repeater can be set up nearly anywhere, including someone's car on a hilltop, they can be rapidly deployed wherever they are needed in a short period of time.

The first thing to remember about emergency operations is that communicating the message is the key. If a simplex repeater becomes an unwieldy due to its rather unnatural "store and forward" method, don't use it. But, if users have had practice drills using a simplex repeater (highly recommended!) then it becomes a more effective communications method.

Unless the simplex repeater is well known, it may be a good idea to remove any CTCSS tone. This will enable a user who may not be a regular user of the simplex repeater to access it during the emergency. If CTCSS is desired or necessary, then frequent announcements of the tone should be made.

If the need for prominent communications are a concern, then setting up a simplex repeater on a popular simplex frequency may be necessary. If most of the local duplex repeaters have been knocked off the air, it may be desirable to set up the simplex repeater on the repeater's input/output pair. This will somewhat mimic the disabled repeater's operation enough for communications to get through if the simplex repeater's receiver is listening to the duplexed repeater's input and transmitting on its output.

Conclusion

No matter how your simplex repeater is used, encourage other hams to use it. This will create a body of users that, in an emergency, will be simplex repeater savvy. Encourage your local or emergency management group to run occasional tests and drills on your simplex repeater. Emergency use will help to justify your simplex repeater's existence during the normal times and foster an atmosphere of mutual respect from other hams.