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Author Topic: Matrix Comms (Part 2)  (Read 32105 times)

Pete Erskine

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Re: Matrix Comms (Part 2)
« Reply #30 on: February 05, 2013, 02:42:25 PM »

What is the function of the LCL in and out sockets on the top row of the patchbay?

Local xlr adapters on front and back of the rack.
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Pete Erskine
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Neil White

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Re: Matrix Comms and Wireless
« Reply #31 on: February 05, 2013, 03:32:48 PM »

We interfaced three repeaters and 8 RTS systems in this show.

I'd be interested in discussing wireless comms and their usage in more detail. I understand the technical differences between full duplex comms, like the telex BTR systems, and semi duplex & simplex systems that are typically based around two way radio equipment.

I know in a large system like the Olympics, there were a lot of radio channels, both semi duplex and simplex. I understand the choice of full duplex comms for users that need to be able to talk and listen at the same time, or for those people who's communication is critical for safety reasons (automation etc) What are some of the factors that are used to decide whether a radio channel should be semi duplex or simplex? In a large system is it typical for a department to have more than one radio channel? Are some channels such as ShowCall set to constantly transmit for the duration of the show?

How are the antenna systems typically deployed for both large shows with dozens of repeater interfaces and shows with just a couple of radio channels interfaced to the comm system?

Neil
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Pete Erskine

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Re: Matrix Comms and Wireless
« Reply #32 on: February 05, 2013, 04:09:11 PM »

I know in a large system like the Olympics, there were a lot of radio channels, both semi duplex and simplex. I understand the choice of full duplex comms for users that need to be able to talk and listen at the same time, or for those people who's communication is critical for safety reasons (automation etc) What are some of the factors that are used to decide whether a radio channel should be semi duplex or simplex? In a large system is it typical for a department to have more than one radio channel? Are some channels such as ShowCall set to constantly transmit for the duration of the show?

How are the antenna systems typically deployed for both large shows with dozens of repeater interfaces and shows with just a couple of radio channels interfaced to the comm system?

Semi duplex repeaters can be connected to the comm system and when in constant TX all the users can hear the PL channel even when someone else is talking on the radio.  The only person who can't is the transmitting radio.

The radio system on the Olympics use special high power tuned combiners to create a single TX path for the antenna.  Usually there are separate TX and RX antenna systems and both antennas are often duplicated in several places such as on the top of the building, in the tunnels under the stands and in any other place which needs coverage.

Simplex radios are just another radio which the comm system can key the PTT and talk to the channel.  Since this function can be done by a single radio and the Main system antennas are broken up into RX and TX a method needs to be used to split this function of the simplex radio.  Either the RF output goes through a relay switching it into the TX antenna system upon PTT or you use separate radios for TX and RX and just mute the RX radio when transmitting.

In the Beijing Opening Ceremony we had over 50 radio channels interfaced to the system which filled 8 equipment racks.  In London it was less but still a lot.

Here are the system names for Beijing.
« Last Edit: February 05, 2013, 04:17:33 PM by Pete Erskine »
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Pete Erskine
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Neil White

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Re: Matrix Comms and Wireless
« Reply #33 on: February 05, 2013, 04:47:15 PM »

Semi duplex repeaters can be connected to the comm system and when in constant TX all the users can hear the PL channel even when someone else is talking on the radio.

Simplex radios are just another radio which the comm system can key the PTT and talk to the channel.

So genereally, a semi duplex radio channel is going to be necessary when you need to monitor or contribute to a PL that may have multiple paticipants on the wired side of the system. A simplex channel only allows one person on either side of the wireless or wired system to communicate at a time.

I would think this makes simplex a good choice for simple communications during the set up phase and for non show critical channels, but a semi duplex channel is a better choice for departments that require significant co-ordination during a show such as Stage Management.

Is it typical to use separate tx and rx antenna for each repater in a system with just a couple of radio channels or is it more common to use combiner and splitters to the RF to each repeater.

At the Olympics did you use standard Riedel RIFace interfaces with Motorola radios for channels that are in constant transmit or does it need to be a specific repeater capable of maintaining the 100% transmit duty cycle? Were the transmitters switched into constant tx mode by a GPIO interface? If so I guess the programming would be the same as discussed in the other thread but with a latching key on a panel to trigger the PTT.

N.
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Pete Erskine

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Re: Matrix Comms and Wireless
« Reply #34 on: February 05, 2013, 07:12:50 PM »

So genereally, a semi duplex radio channel is going to be necessary when you need to monitor or contribute to a PL that may have multiple paticipants on the wired side of the system. A simplex channel only allows one person on either side of the wireless or wired system to communicate at a time.

I would think this makes simplex a good choice for simple communications during the set up phase and for non show critical channels, but a semi duplex channel is a better choice for departments that require significant co-ordination during a show such as Stage Management.
The main reason for semi duplex over Simplex is the better coverage area afforded by using a repeater.  Constant TX and comm interface only are features which enhance this repeater function.

Quote
Is it typical to use separate tx and rx antenna for each repater in a system with just a couple of radio channels or is it more common to use combiner and splitters to the RF to each repeater.
Combiners for TX and RX in a large radio system are quite different.  TX needs high power and isolation of the TX inputs.  RX just needs low power rf distribution. 

On a very small show each repeater might have a tuned duplexer to make a single antenna for X and RX on a simplex radio.  This has the disadvantage that the radio frequency can't easily be changes since the duplexer must be re-tuned as well.  For a repeater with separate RX and TX systems you can also use a duplexer with the same limitations.  On the event I did in January, I asked for 5 repeater pairs to be programmed into the system knowing that I only was going to use 3.  Good move since when we got to the site channel 1 of the repeater had some other constant TX system on the channel and we couldn't use it.  Not using duplexers and instead separate RX TX antennas made it ok to change channels.

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At the Olympics did you use standard Riedel Riface interfaces with Motorola radios for channels that are in constant transmit or does it need to be a specific repeater capable of maintaining the 100% transmit duty cycle? Were the transmitters switched into constant tx mode by a GPIO interface? If so I guess the programming would be the same as discussed in the other thread but with a latching key on a panel to trigger the PTT.

In Beijing it was Riedel Riface radios but in London the spec called for an Australian radio to be used.  Both were able to const TX with no problem.  On the Artist a gpo command was part of the vox 4-wire input command so anytime the port was receiving audio the PTT was activated. 
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Pete Erskine
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Neil White

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Re: Matrix Comms (Part 2)
« Reply #35 on: February 06, 2013, 07:07:33 AM »

Desktop panels are the nicest to use just because they are desktop, however making an adapter box for the audio I/O and GPIO cant be really done cleanly.  Rack mount panels, like the method used by Clair Broadcast (Wireless First) are more usable.  The tiltable 2RU boxes can be stacked and the back panel on the rear affords a full implementation of all the I/O GPIO and secondary headset ports.

I have used Whirlwind's free DesignPro software to put a panel design together for a Riedel RCP. Is there anything else that should be included?

Neil
« Last Edit: February 06, 2013, 07:09:26 AM by Neil White »
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Neil White

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Re: Matrix Comms and Wireless
« Reply #36 on: February 06, 2013, 07:17:44 AM »

In Beijing it was Riedel Riface radios but in London the spec called for an Australian radio to be used.  Both were able to const TX with no problem. 

Were these the RF Technology base stations as used extensively by the PA People?



It sounds like there was no alternative option in the spec, otherwise I would imagine Riedel would have used their Riface radios. Were there any technical advantages to the RFT radios?

Neil
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Chris Johnson [UK]

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Re: Matrix Comms (Part 2)
« Reply #37 on: February 06, 2013, 08:22:14 AM »

Bear in mind that a RiFace is just a housing for a pair of Motorola GM radios. Lots of companies i know make their own such housings, with the necessary PSUs, audio interfacing, etc...

Any radio base that will accept line level in and out will work fine. I mainly use the Tait TB7100s. They are nice because they have internal duplexers, and are 1u. They will do constant duty at 40w TX.

The manfrotto magic arm implementation is a great idea. One for the future for sure.

Sometimes I find that having a comms system which isn't based around AES is more flexible for the specific events that I'm doing. Partly because it allows distribution of panels down existing audio infrastructure. I carry breakouts for CC or RTS matrixes that split a port into 3 XLRs (Send, Return, Data). Additionally, traditional analog interfacing allows me huuuuge cable runs on cat5 very easily.

I did the Torch Arrival segment of the opening ceremony, which required comms panels to be distributed along the canal/river that runs through the olympic park. The matrix was under the main footbridge (that ran between Aquatics and Water Polo). I was happily running panels over 600m off cheap, installation grade cat5 that we treated as a consumable and disposed off at the end of the event.

So, AES is cool, but In my world, where I'm working with live music mainly, audio is still all analogue, so sometimes having a matrix that works that way makes for easier interfacing.

One of the reasons I'm interested in something like a Clearcom Eclipse Median is the sheer number of options for interfacing. You can connect a V series panel via traditional 4w+D, IP or via their 'DIG2' system which basically uses a single twisted pair for a panel. Meaning you can run a matrix panel over a single mic cable.
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Pete Erskine

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Re: Matrix Comms (Part 2)
« Reply #38 on: February 06, 2013, 08:57:34 AM »

I have used Whirlwind's free DesignPro software to put a panel design together for a Riedel RCP. Is there anything else that should be included?

Neil

I would include the Ext mic in, A duplicate of HS A on the rear and a 5 pin headset wired as a stereo HS using the mic and ear from A and the other ear from B.  Also a female Power connector in parallel with the input for aux equipment.  The audio out and in connectors should be transformer isolated.
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Pete Erskine
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Pete Erskine

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Re: Matrix Comms and Wireless
« Reply #39 on: February 06, 2013, 08:58:29 AM »

Were these the RF Technology base stations as used extensively by the PA People?

Could have been them.
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Pete Erskine
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ProSoundWeb Community

Re: Matrix Comms and Wireless
« Reply #39 on: February 06, 2013, 08:58:29 AM »


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