Using Toronto Repeater for International voice conference

 

 

Background

We started using Toronto repeaters with IPHONE patch to serve International conference since late 1997. We have conducted several conference sessions between hams of various Cantonese speaking areas with this practice. Result had been quite satisfying yet one major issue had been experienced:

We didn't have sufficient IPHONE ports available in Toronto!

That was a key limitation for us on connecting parties to join the activity. It is clear that a new digital voice platform (which can carry multi users voice conference within 28.8kbps bandwidth) is needed. It is really a relief that our Vancouver participants brought our attention to software VOXPHONE. This software supports neither video nor application sharing, but it does support voice conference to a maximum of 5 users. Reproduced voice quality can match up IPHONE during adverse condition. It is H323 compatible. It therefore can cross work with other H323 standard voice software (although the conference feature will not be available under such situation). Based on this reason, we recommend this new software as the basic platform for our future conference activities. IPHONE and Net-meeting can be used as auxiliary platform provided more Toronto Hub ports are available.

Following is a diagram to show network configuration under such a new environment.

Click on the pictures to obtain higher detail

 

 

Software platform in detail

VOXPHONE can connect target parties through four methods:

Among the above methods, using VOXPHONE server or Email address to connect calls depends highly on the stability of the VOXPHONE server plus knowing precise spelling of the target's posted name. Unlike IPHONE, VOXPHONE server does not support channel/chat room filtering. This made it very labor intensive to identify users from non-ham users who are also posted by the server. The other connecting options are basically direct TcpIp connecting. ICQ is by far the easiest way to exchange update TcpIp address between internet-users. It has two important basic features that will be highly needed for our operation: 'chat conferencing' and 'info posting'. If you do not have ICQ yet, we highly recommend to have it installed first. Please click on the following button to connect with ICQ headquarter, choose the most suitable ICQ version for your system. Have it installed and registered for you UIN (universal identification number).

If you have difficulty to find VOXPHONE software, contact me on aa656@torfree.net.

Conference session set up and operating procedure

Once you have ICQ up and running, have the UIN of the last known TORO hub ports (as posted in Chinese speaking hams home page) be added in your contact list then look for information posted about the update Cantonese conference time table.

To join or listen to our conference, show up through ICQ on the arranged time and contact one of our listed TORO hub ports (send him a short ICQ message). The TORO hub port will then call you back via ICQ chat session. Once you are in the chat. You will then be notified on an assigned TORO hub port via the chat session. You can then boot up the voice conference platform agreed upon or just sit back and wait for a call from him. As soon as the audio channel is up, you are one of the participants in the conference. If problems are encountered, always use the chat session to inform your assigned TORO reception first. Basically ICQ chat session is a control channel to conduct operation while VOXPHONE or equivalent session is the audio channel which patches you into the conference.

Since voice portion of conference is carried via amateur radio frequencies, all talking participants need to follow full ham radio communicating procedure. Users outside Ontario will be treated as temporary visitors to Toronto. Please identify yourself with your original call sign plus '/VE3' suffix).

If a private contact is required with any other VOXPHONE participants (not a radio user linked via other VOXPHONE hubs) of the conference, simply use the chat session to inform your assigned TORO hub port and the target station (if he is on the chat session as well). Then set up a separate VOXPHONE session to this user.

Additional hardware for Internet hub drops

For participants serving as hub ports (dropping audio from Internet circuit to radio links), additional hardware is required to couple computer sound card with radio transceiver. The easiest way is to find a radio which has built in vox (voice operated transmission). Following is a simple circuit diagram showing a way to connect sound card with such a kind of radio. This configuration will be suitable for both VOXPHONE and IPHONE application.

 

 

If external vox circuit is required to drive the radio, click here for details .

 Hardware and software setting for internet hub ports

Sound card and software set up

The computer sound card used should have at least two audio I/O ports. Line in (or mic.in) accepts audio received from radio. Speaker out (or line out) serves two purposes. Audio from this output is used to modulate transmitter. The are responsible for controlling transmit action while PTT key up action is executed via voice operated transmit circuit. Due to such VOX natured key up, there are some special precautions that have to be taken. Key issue is to maintain stable delivery of audio. Audio from active receiver must not be appearing at the line out port. This practice is needed because audio from computer drives PTT circuit. If 'line out' port can include audio monitored from 'line in', sound source will contain looped back audio of the receiver channel. Once such audio is sensed by the vox circuit, the transceiver will be put into transmit stage while those 'received' audio will immediately disappear due to lack of sound source. This will cause an endless loop of attempt to transmit. For this reason, audio mixer (inside window) has to be set for 'record line in enable' but 'playback line in disable'. This is a standard feature in most sound card but I had seen models having a driver that cannot do that. In that case, the sound card has to be changed to a full SB16 compatible model before the job can be done. Click the following link to take a look at our suggested setting of VOXPHONE software for this application.

Radio link environment

Only one user can talk into the Toronto repeater while all other members have to wait and listen. It is better to have all hub ports set as SIMPLEX mode only. Enabling full duplex mode of Voxphone will only create interference if more then one hub drop try to talk into the net at the same time. Radio links connected behind internet hub ports (except Toronto hubs) must not be a radio facing a second repeater system. This is to prevent squelch noise or courtesy beep of such system from causing unsteady transmission at Toronto.

 Feel free to Email me if more detail required.

 

Patrick Wong 02/Jan/99.

 

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