G4EID.co.uk - Voice Internet Linking Gateways
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User Guide

There's more information for users available here at QLV.it.

First a brief explanation. For the history and development of the (I)nternet (R)adio (L)inking (P)roject, please refer to the official IRLP site here, it explains far better than I ever could what itís all about and where it came from. 

For those who want a quick explanation of it, itís a means of linking two radios together using VOIP (Voice over Internet Protocol) with, not surprisingly, the Internet as the communication medium. If a system is set up correctly, and has sufficient bandwidth, youíll be hard pushed to tell that the station youíre listening to is not a local one.

Unless you've used voice internet gateways before, it might all seem a little unclear, but in reality it's very simple. If you are intending to use the facilities here, all I ask is that you read these instructions first. Most of it is common sense, but it doesn't do any harm to cover some old ground.

The first and most important difference is that the nodes at G4EID are SIMPLEX voice internet gateways. That is, unlike a repeater, it can either transmit or receive at any one time, not both. If you listen to a repeater, it repeats what it hears on its input frequency onto its output frequency. In other words, listening on the repeater's output let you hear everything that's going on. On a simplex gateway, the only way you're going to hear the local station using the gateway, is if you can hear that station directly.

Imagine for example you're in Preston, with an outside aerial, and you can normally hear the gateway at S9 plus when itís transmitting. You arrive in the shack and switch on, you hear nothing. All clear you think, and you dive in and try and connect the gateway someplace for a QSO. Think however, of the poor guy in Southport town centre, who at that very moment, is running milliwatts from his hand portable, using the gateway on a regular contact to his mate in the USA. He's getting into the gateway just fine because he's close to it, but you can't hear him. Result? You walk right over him and wreck the contact. So, golden rule number 1

RULE 1 - LISTEN, LISTEN and LISTEN again (for at least 5 minutes) on the frequency to check that the gateway really is free. If you're really wanting to find out quickly, you can key a "*3", this will then announce whether the node is free or busy. It's always better to listen first though.

Ok, so you're sure it's free and you want to use it. Now what.

For a start, don't worry about any 1750Hz toneburst, itís not required here. The node won't "blip" up either, it's not designed that way. What is required though, is CTCSS. And the reason? Well without it, anything on the channel, for example another amateur using the frequency, (but not intending to use the IRLP node), or some local QRN will be heard by the node radio. If at that time, the node is connected to a reflector (more of which later), then that signal (whatever it is) gets re-broadcast to every other node connected to that reflector. The entire reflector channel is rendered useless to dozens of people all over the world. And the final result? Within minutes, the noise is traced to its source (G4EID) and the node is then barred from joining that reflector again. So golden rule number 2

RULE 2 - A CTCSS tone of 79.7Hz (5230 & 5240), and 123Hz (5973) is required on your transmission to access the gateway.

Ok, you've listened and established it's free, you've enabled the appropriate CTCSS tone on your transceiver, now what? Well, you need to know where you want to call! IRLP has two modes of operation. Either way, you're going to need an up to date list of nodes. The current list can be obtained by printing the one on my web site here, it's a list sorted by Country and State.

The two modes are direct, (Gateway A connects to Gateway B), or by use of a reflector. Let's take the first case because it's easier to explain.

Point to point (direct). In this mode one IRLP gateway is linked to another. It is important to remember that while a gateway at G4EID is connected to another node, no other connections (either inbound or outbound) are possible until the existing connection is closed. You establish a "link" between the gateway and another one of your choice. Whilst linked, anything that you transmit is re-broadcast on the remote end and vice versa. This enables the contact to take place. So, an example. Letís say you've got the list and have spotted you may like to see who's around in Dallas USA. You note that the gateway's callsign is N4MSE and its associated node number is 4180. And so to the third rule.

RULE 3 - You'll need a rig capable of sending DTMF tones or a DTMF keypad.

That's because the entire system is driven by DTMF tones. Without DTMF you're lost. So, to call, you've waited and established the node is not in use, you've enabled the appropriate CTCSS on your rig, you press the PTT, announce your callsign, and "dial" 4180, then drop carrier, and listen. That's all there is to it. If you're in luck, you'll get a message back along the lines of "<callsign> <location> link on" Once you've heard this, the path is established and you're away. So, to turn a link on, simply dial the node number. If your rig doesn't have DTMF, all is not lost. Some users have been known to use their mobile phones as the DTMF source!

RULE 4 - Once a link is established, listen a while before transmitting.

Streaming audio over the Internet can introduce some delays, which can be path dependent. Always wait a little while to be absolutely sure you're not going to talk over someone at the other end.

It's best practise when making a call to identify your callsign, location and where youíre calling. For example, "This is G4XYZ, Preston UK listening on N4MSE via IRLP" This is good since in many countries IRLP nodes are interlinked with normal repeaters. Without specific information, some remote users may get terribly confused about what's going on!

Incidentally, itís not considered good manners to bring up a link, then close it again without announcing yourself. Please identify yourself at all times.

Hopefully you'll get a reply and the QSO is underway. But remember about pausing a little before going back. It's also important to wait a second or two after pressing the PTT before talking. This allows the link to stabilise, if you don't do it, the other end is likely to miss your first second or two of audio. So the golden rule(s) when in QSO

RULE 5 - When in QSO, and the transmission is passed back to you, leave a pause of a few seconds before transmitting yourself, then don't speak for about a couple of seconds after that.

This allows other people to join in, and if youíre using a reflector, for other users on other repeaters connected to that reflector, to downlink. If you follow the above rule your contact should be trouble free and youíll not annoy users on other repeaters if using a reflector.

Now a word about timeouts. Firstly, yes there are some. As far as I can make out you've got about four minutes maximum for each transmission you make. If you exceed this, the link will be closed. If you get used to keeping overs fairly short, you won't have a problem.

Your QSO is at and end. What now? Well, as already mentioned don't just end by switching off. Unless there's anyone else wishing to use that link (and you'd have heard that by leaving pauses between transmissions...) agree between yourselves who's going to "downlink" If it's you, key 73, you'll be notified that the link is down.

Your contact is complete.

Reflectors

Previously I mentioned that there are two modes of operation, direct, and via a reflector. So, a word about reflectors.

A reflector is a sort of gateway, but one that doesnít have any radio equipment connected to it. What it does have lots of though, is Internet bandwidth. Thatís because itís there to ďjoinĒ lots of gateways together into one super node.  When youíre connected to a reflector, whatever you say is faithfully rebroadcast to every other gateway connected to that reflector. Think about that, you could be being heard in several continents simultaneously. Remember therefore at all times when connected to a reflector, your audience may be a lot larger than just the guy on the remote repeater youíre taking to.

All that has been described previously applies equally, if not more so when connected to a reflector. You'll find the reflector codes on the nodes list. For example the Sydney reflector is 9500. The concept is very simple, if you connect a G4EID gateway to a reflector (Sydney for example by keying 9500), you'll hear anything that's going on at any other node also connected to that reflector. Which nodes are connected to that reflector can also be found from my reflector status page.  What is important is to pause a little while longer at all the times mentioned above. This is to allow people to switch off links and or call in. In essence, on a reflector, when you put a call out, you're doing it on every node that happens to be connected to that reflector. You could end up in a QSO with two guys, one in the States, the other in Australia, consequently breakfast, dinner and supper can all occur simultaneously on IRLP J

If you wish to hold an extended conversation with someone whilst using a reflector, consider exchanging node numbers and setting up a direct link. Itíll free up the reflector for other users. Guess itís sort of like moving off the calling channel onto simplex J Having said that, if you intend only a short QSO, thereís no problem with doing that on the reflector.

G4EID station ID's

Gateways at G4EID will send a CW subaudible ID at 20wpm at the start of every transmission. It may annoy some, but it's a requirement of the NOV (Notice of Variation) from the Ofcom, sorry. The node will also broadcast a short voice ID every 15 mins (when the node is not in use) and every hour a longer more informative ID. If there has been activity on the frequency in the 5 mins leading up to the long broadcast, a short broadcast will be made instead.

Localisation

There are some special features available on the nodes at G4EID. These are accessible via star codes. Specifically, *1 will inform the user of the last calls into and out of the gateway, *2 will announce the local time, *3 will give the gateway status (i.e. if it's free to use or not), and ** will cause the local weather report to be given.

Summary

It's there to be used, so enjoy it, but please follow the guidelines noted above. If anyone's still uncertain about anything, drop me a line at g4eid@hotmail.com and I'll see what I can do to help. If you think this document could be improved or added to in any way, feel free to call me.

Mark Haworth G4EID-KM8H

Issue 0.48 11/03/2006

 

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