KC6HUR(-L)

Some of the major complaints that people have with VoIP whenever it is used in conjunction with a repeater, are the repeater hang-times, courtesy tones, voice announcement, and IDs are repeated through the Internet connection. While this is annoying at best when only one such station in a network does this, it creates total havoc and eventual collapse of the entire network if two or more stations behave in such a manor. The 2003 911 Commemorative Net is a good example of such behavior where the net had to be dissolved before it even got started, due to all the ping-ponging nodes. During the Hurricane Charlie Emergency Net, ping-ponging nodes had to be banned from the net.

The Major Cause For Problems

Where a node is not directly connected to a link port on a repeater controller, there needs to be a method for the repeater to signal the node that the user talking on the repeater has stopped transmitting. Some of the popular VoIP software packages (EchoLink and eQSO) use VOX (Voice Operated Transmit) to control when the node is sending to the Internet. Therein lies the problem. Any sound emitted by the repeater triggers the VOX causing these sounds to be sent over the Internet connection. When this extraneous transmission is received at a distant connection, causing that repeater to key up AND the VoIP node has a similar configuration, when the first node unkeys, causing the remote node to then unkey, the remote node VOX then hears the courtesy tone from it's repeater and starts sending over the Internet, which then causes the first VoIP key up it's repeater. When the remote unkeys causing the first node to unkey, the first node hears it's courtesy tone, keys up again and the whole process continues until someone breaks the connection. This is called ping-ponging or deadly embrace.

The EchoLink software has the ability add delays to the VOX so that a signal has to be present for a longer period of time before data transfers begin; however, this increases the amount of time someone must talk before the node begins sending, thus chopping the beginnings of their transmissions to the network. Setting the release times to a short time to help reduce the hang-times, causes transmissions to chop between words, again making it difficult for the system to coherently transmit intelligible voice.

Other VoIP systems (IRLP) use COS to control the nodes sending to the Internet. While this method does not suffer the problems of chopped words words due to aggressive VOX settings, it can still cause ping-pong problems if the COS is not also qualified with CTCSS.

I'm unable to talk to WIRES-II as that is a pretty closed system and I have no access to it; however, I can only assume that it works in a manner very similar to IRLP.

How To Make It Work Better

When connecting a VoIP system to a repeater, it is best to use a radio that has Tx and Rx CTCSS AND for the repeater to which the node is connected to use CTCSS on it's input and output. It is not sufficient have CTCSS on the repeater out if the CTCSS is controlled by the repeater PTT, the CTCSS tone on the output of the repeater MUST follow the input COS and/or CTCSS. This means that while has a user transmitting on the input, the output CTCSS is turned on. The CTCSS tone on the repeater output should be turned off as soon as the repeater input signal goes away. Therefore, even though the repeater may have a 10 second hang-time and a courtesy beep, the VoIP node radio will remain quiet as long as there is nothing on the repeater input. This way the radio on the EchoLink node stays silent except for when someone is transmitting on the repeater input. IDs, voice announcements and such do not assert CTCSS on the repeater output; therefore, node radio will not send them out over the Internet. Of course, any ID that comes from the repeater while someone is talking on the input will be heard, but that is acceptable.

Just A Little Cooperation

This type of configuration does require that you coordinate your node operation with the repeater owner. If you take the time to configure your node and repeater to operate in the manner described above, you (and others) will find your VoIP experience to be much more enjoyable. You might even find that you will be more welcome to join various nets instead of being banned because of a poorly configured system.