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IEM v's receivers


the kid

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I was trying out a theory the other day, someone wanted to run sound in 2 local but big cable run locations. My solution was to use the TX from our sennheiser g3 IEM and the RX from our sennheiser g3 mic packs, tuned to the same frequency.

 

The logic worked in that I could tune but for some obscure reason they refused to talk to each other, is there something in the g3's that stop this being allowed ?

 

Same principle with some older belt packs I found, they will work the frequencys but wont actually "tune in"

 

Any ideas?

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Defo the pilot tone, its designed so that when the RX looses signal it mutes as the FM receiver generates a high level of broadband noise when it's not receiving a signal.

 

Im pretty sure the IEM TX don't transmit the Pilot tone, either that there not compatible as I have only ever got it to work with the pilot turned off. just be careful if you turn the TX off before receiver, it will be very loud and unpleasant.

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Right - correct settings are transmitter = stereo off. The IEMs are capable of stereo, and the stereo setting produces a rather thin and strange sound on the mono receiver. The twin channel bandwidth is different and the transmitter needs to be in mono - which is stereo off on the display.

Receiver just needs pilot tone set to off. With it engaged you get silence. Other than that, just gain settings to get right on the TX, putting in appropriate settings to maximise S/N without overloading.

Just set the displays like this and it works.

http://www.limelight.org.uk/iems.JPG

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Defo the pilot tone, its designed so that when the RX looses signal it mutes as the FM receiver generates a high level of broadband noise when it's not receiving a signal.

 

Im pretty sure the IEM TX don't transmit the Pilot tone, either that there not compatible as I have only ever got it to work with the pilot turned off. just be careful if you turn the TX off before receiver, it will be very loud and unpleasant.

 

 

Honestly never even considered pilot before, do all mics have it ? and why the noise if you have no pilot? It does explain the issue I had with another mic though.

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Pilot tone is a good addition to squelch in that it stops noises from other systems getting through. Spurious interference on the operating channel won't have the correct tone present so the receiver mutes the output. It also stops another manufacture's system opening your receiver. This isn't much of a benefit as you still have two people on the same channel, but it's useful for a bit of extra security.

 

As a bit of side-chatter, a similar system is in operation on those cheap (and often nasty) PMR446 walkie-talkies. This uses a frequency lower than the voice spectrum to do a similar job. Those cheap walkie-talkies often talk about 36 channels, but there really are just 6 frequencies - but each one uses a sub-audible tone to do the same thing as our radio mics. Channel one is the first frequency, and then has 6 different sub-audible tones selectable. Multiply this up by the 6 channels and they 'appear' to have 36 different channels. However, if somebody else is using your frequency, you get interference - but you don't hear them because their tone is different. This often means people think the radios are faulty. You try to call the other person, but because somebody stronger than you is on the channel, your message doesn't get lost - but your other radio stays silent. Neither end can work out what is wrong. The weaker signal intrudes on the working one as weird noises in the background - just like our radio mics - but if you hear a recognisable voice, it's no good saying "who was that?" because they won't hear you either!

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