Links to Other Networks

Coastal Emergency Linking System

Below is the most recently approved linking map and a table containing the same information as seen on the map. Below that table is a description of how the system works and an example of how to use it. Any licensed amateur may use the system but please be courteous and give priority to the net if it is active, especially during emergency operation.

The linking system is rather straightforward in how it operates. The KX4NC Columbia UHF (443.300) repeater and antenna live on the WUND-TV tower at 1,200 feet. This provides an effective range of ~65 miles from the tower site and by itself is a great repeater but is also the backbone for the linking system. Repeaters that are in the system can be linked to the backbone with the appropriate DTMF codes. All repeaters that are linked to the backbone essentially become one large network that passes traffic from any one of the linked repeaters through the backbone and out to all other linked repeaters.

The details of what is going on behind the scenes are each repeater has a dedicated link radio that is on the Columbia UHF frequency. When we, for example, are using the K4OBX Hatteras repeater we can enter DTMF 151 and this will cause the Hatteras repeater to activate its link radio and respond with some audio confirmation after you unkey. Hatteras is now patched into the Columbia UHF backbone. Any transmissions on the Hatteras repeater will also be heard on Columbia UHF and vice-versa. Now let’s say we want to contact someone who may be listening to the Greenville repeater. We can enter DTMF code 91 and this code will be heard by the Hatteras repeater, be sent out by its link radio, go through the Columbia UHF backbone, and be heard by the Greenville link radio which will cause the Greenville repeater to activate and join the fun. Now any traffic that goes into Greenville, Columbia UHF, or Hatteras will go through the Columbia backbone and in turn be heard on all three repeaters.

As mentioned before any licensed amateur radio operator is welcome to use the system. Just please be courteous and bring any links down that you have brought up. The way to do this is by entering the DTMF down codes for each repeater you brought up but in reverse order. For our Hatteras example above, best practice would be to announce your callsign followed by “bringing down the links” followed by DTMF 90 and unkey your radio. Listen for Greenville to confirm it has come down and key up to enter DTMF 150 to bring down the Hatteras link which after unkeying you should hear Hatteras confirm its link is down.

Linking to Columbia VHF (146.835) works in the same way as other repeaters on the system, if we wanted to include Columbia VHF in our Hatteras example above, we would enter DTMF 11 after Hatteras is linked to the backbone. The Columbia UHF backbone would hear this and link in the Columbia VHF repeater. Just be sure to bring this down as you would with any other link before your local repeater is disconnected from the backbone.