sergiofucchi Posted June 3, 2013 Report Share Posted June 3, 2013 I recently had the interference between two transmitters SMDB/E01 attached to the belt of two actors who were sitting next to each other. It is normal or not? Sergio Quote Link to comment Share on other sites More sharing options...
jason porter Posted June 3, 2013 Report Share Posted June 3, 2013 It is possible. Separate the transmitters as much as you can. How close were the receivers to the transmitters? This is a case where you do not want the receivers too close to the tx because they can cause interference on each others receiver. Quote Link to comment Share on other sites More sharing options...
john Quinn Posted June 3, 2013 Report Share Posted June 3, 2013 No it should not happen .Check they are set up properly ie there is a reasonable amount of separation between the TX frequencies . Best John Quote Link to comment Share on other sites More sharing options...
sergiofucchi Posted June 3, 2013 Author Report Share Posted June 3, 2013 It is possible. Separate the transmitters as much as you can. How close were the receivers to the transmitters? This is a case where you do not want the receivers too close to the tx because they can cause interference on each others receiver. About 5 meters... Quote Link to comment Share on other sites More sharing options...
RPSharman Posted June 3, 2013 Report Share Posted June 3, 2013 Use FreqFinder app to be sure frequencies are compatible. Actors are near each other all the time. Quote Link to comment Share on other sites More sharing options...
studiomprd Posted June 3, 2013 Report Share Posted June 3, 2013 (edited) " It is normal or not? " it depends... it is certainly not desirable, but if your frequency selections conflict, it is possible... " Actors are near each other all the time. " typically, there is virtually no minimum distance required between properly tuned transmitters, and in many cases people wear multiple transmitters what happened when you changed frequencies ?? you did try some frequency changes, didn't you..? though of course, there could be a problem... " the interference between two transmitters SMDB/E01 attached to the belt of two actors " and, are you certain there is not something else in the equation ? Edited June 3, 2013 by studiomprd Quote Link to comment Share on other sites More sharing options...
jason porter Posted June 3, 2013 Report Share Posted June 3, 2013 5 meters shouldn't be a problem. Did you have anything in your bag or on your cart that could have caused short range (like a recorder)? I recently experienced short range on my RFs due to a very bad BNC cable on the camera (feeding an onboard monitor) About 5 meters... Quote Link to comment Share on other sites More sharing options...
VM Posted June 3, 2013 Report Share Posted June 3, 2013 interference between two transmitters Are you sure that it comes from the two transmitters ? There are so many DVBT (and others wireless) chanels in Italy ! Did you do a scan ? Did you changed frequencies ? Quote Link to comment Share on other sites More sharing options...
jason porter Posted June 3, 2013 Report Share Posted June 3, 2013 Good point, that should always be your first step. Are you sure that it comes from the two transmitters ? There are so many DVBT (and others wireless) chanels in Italy ! Did you do a scan ? Did you changed frequencies ? Quote Link to comment Share on other sites More sharing options...
Andrew Rowe Posted June 4, 2013 Report Share Posted June 4, 2013 typically, there is virtually no minimum distance required between properly tuned transmitters, and in many cases people wear multiple transmitters what happened when you changed frequencies ?? you did try some frequency changes, didn't you..? It's certainly true that having two transmitters on a single actor/presenter works and is standard practice on some productions. Nevertheless, having transmitters in close physical proximity to one another will exacerbate intermodulation between the two frequencies. Each transmitter will pick up the other's signal, and will retransmit the resultant intermodulation products - for example, take a read of this (old) Sennheiser document: http://en-uk.sennheiser.com/downloads/download/file/2066/User_Manual_pro_US.pdf (which also backs up Jason's point about keeping transmitters a few metres from receivers). Consequently, Lectrosonics recommends keeping transmitters 3-5 feet apart when testing frequency plans (as per the Venue manual). Of course, this is with the transmitters in free space, which increases the effective power output significantly compared to a body worn transmitter (by about a factor of 5). Taking this into account, it's beneficial to keep body worn transmitters at least 1 foot apart - as will usually be the case. A decrease in the power of both transmitters (e.g. from 250mW to 50mW) may also help when they are side by side. This problem normally doesn't manifest itself in practice, since actors usually face one another with their bodies between the transmitters. And, when it does manifest itself, it will usually do so as a slight reduction in range, which people might put down to other factors if they notice it at all. If you are getting actual splats and audible interference at 5m though, there is probably some problem in the choice of frequencies in the first place, which may only become apparent when the transmitters come into close proximity. It is easy enough to test when you get chance. Quote Link to comment Share on other sites More sharing options...
studiomprd Posted June 4, 2013 Report Share Posted June 4, 2013 A huge part of our job is problem solving... " It is easy enough to test " troubleshooting 101 Quote Link to comment Share on other sites More sharing options...
sergiofucchi Posted June 5, 2013 Author Report Share Posted June 5, 2013 I did a scan of the free frequencies for each receiver. A transmitter was on the block 19 and the other on the block 20. Sergio. Quote Link to comment Share on other sites More sharing options...
studiomprd Posted June 5, 2013 Report Share Posted June 5, 2013 " I did a scan " good start... (repeating what happened when you changed frequencies ?? you did try some frequency changes, didn't you..? (frequency coordination spans all "blocks") and, are you certain there is not something else in the equation ? Use FreqFinder app to be sure frequencies are compatible. Actors are near each other all the time. email Lectrosonics for frequency coordination tips follow Lectrosonics for set-up and walk testing multiple systems having transmitters in close physical proximity to one another will exacerbate intermodulation between the two frequencies. Each transmitter will pick up the other's signal, and will retransmit the resultant intermodulation products - for example, take a read of this (old) Sennheiser document: http://en-uk.sennhei...nual_pro_US.pdf though of course, there could be a problem... If you are getting actual splats and audible interference at 5m though, there is probably some problem in the choice of frequencies in the first place, which may only become apparent when the transmitters come into close proximity. It is easy enough to test when you get chance. A huge part of our job is problem solving... something may need to be tuned or repaired... Quote Link to comment Share on other sites More sharing options...
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