The title of this topic says it all. What am I talking about?
Let me try to explain.
Firstly if your link, repeater, node, station etc. uses VOX then you are a good candidate to cause havoc on the GRHub- / ZS - Link Network. Echolink has VOX as a future and on several occasions in the past I had to disconnect stations that lock up the system or causes a Ping-Pong Loop. PLEASE do not use VOX when linking to the GRHub Network (ZS1I-L). If I find that your station /link / node is using VOX I will disconnect your station and you will be informed not to use VOX on the Network. No I do not play policeman, but we need to play the game here. Your station not only influence the GRHub Network if you use VOX but also all the stations connected to the world wide network.
Secondly if your link, node or repeater has a long "tail" (squelch burst often heard at the end of a transmission as the PTT is released) please adjust this tail to be as short as possible or switch the tail off. The best squelch "tail" elimination method is when the tone stops just before the hang timer unkeys,this works well with all brands of equipment. Most good repeaters or controllers have the option to select the tail off or on. I do understand that some repeater custodians prefer to have a tail on their repeater. If you do link to the network then please make this tail as short as possible.
A long "tail" if not setup correctly will cause endless ping-ponging. More on this below.
Early repeaters used relays to key the transmitter in response to the receiver detecting that a signal is present. Some propagation effects, such as mobile flutter, or picket fencing, would cause the repeater transmitter to cycle on and off as the receive signal experiences fading and restoration of received signal. This cyclic operation would result in premature failure of the transmit relay. Further, the delay in keying the transmitter may itself be responsible for rendering a signal unintelligible when compared to leaving the transmitter keyed during periodic momentary signal fading conditions.
These problems were mitigated by implementing a squelch tail timer. As soon as the receiver detects a valid signal, the transmitter is keyed immediately. When the received signal drops out, a timer is started and the transmitter remains keyed until that timer times out. The squelch tail timer duration is longer than most periodic signal fading conditions, and is able to avoid un-keying the transmitter in instances of periodic fading conditions.
Secondary to this function, the squelch tail serves a second purpose in providing a queuing signal to indicate when a user station may begin transmission. Stations may begin transmitting after the repeater squelch transmitter drops. This can be identified by the sound of the repeater squelch decaying being re-transmitted by the repeater transmitter when the receive signal drops out of the repeater receiver, followed by a delay that is equal to the duration of the squelch tail timer, and then the sound of the squelch decay heard directly on your radio when the repeater transmitter drops. Although the squelch tail timer duration typically is approximately 1.5 seconds long, shorter and longer squelch tail delays may be present on a given repeater system.
This double decay of squelch circuits, resulting in short noise bursts that are separated by a 1.5 second delay, is often referred to as a ker-chunk sound, or simply the squelch tail (it is not a come-back).
The squelch tail is used in repeater operating protocol to indicate first, that the transmitting station has ceased transmission as evident by the first squelch decay noise burst, and second, that the repeater transmitter has stopped transmitting as evident by the second squelch decay noise burst. Conversing stations should not start transmitting until the second squelch decay noise burst occurs. Breaking stations should transmit in the interval between noise bursts, as conversing stations will be standing by to wait for the repeater transmitter to drop, in order to make their presence known.
This is very important when two repeaters are linked to each other, to prevent endless ping-ponging of one repeater bringing up the other.
Thirdly I request that a station do not connect to more than one station/node that is already connected to a specific station on the network. This will also result in ping-ponging and audio loops. Always check who is connected to who before connecting to a station, repeater, link etc.
Fourthly - If at all possible connect the Internet to your repeater, node, link etc. on site. That way, there is no hang time to propagate back into the network. Alternatively connect the Echolink/AllStar node to a link port on the existing repeater controller, which has the advantage that if the AllStar/Echolink box dies, you still have local repeater functionality. The other advantage of having the node at the repeater is better audio quality. You can successfully setup a link on the user frequency, but you need to take steps to ensure that the hang time is not seen by the node, such as using CTCSS gated by the receiver's COS.
Finally: The above might sound cumbersome and technical but unfortunately this is the only way to prevent the dreaded Ping-Pong Loop effect. Either we do it right or don't do it at all. A half-baked system is not going to work effectively and will only lead to frustration and bad operating practices, nothing that we need or want in amateur radio. We must be proud and professional in this regard. Let's play the game and enjoy the ZS Link Network in South Africa.
More information and links:
1. The use of "AND Squelch" to eliminate those annoying squelch bursts. By Kevin Custer W3KKC
2. Echolink Sysop Settings By K1RFD
