Nicktaylor Posted April 28, 2015 Share Posted April 28, 2015 We had ten channels set up on the Sennheiser spaced frequencies and at least twice in the week for no obvious reason the RX units started to sequentially over-mod. The first time we thought it was power spike or something like that as the was a flicker causing macs to reset. However there was surge socket in the way. I will try to attach the image one of the young ops filmed. On the sound desk you could see the peak lights sequencing through in order as well. After about a minute of so things sorted themselves out https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=37e2816bc7&view=att&th=14cff316c0918d61&attid=0.1&disp=safe&realattid=1499684476702162944-local0&zw&saduie=AG9B_P_F7tEAkVi05hP4ddMZ0J5l&sadet=1430211363315&sadat=ANGjdJ-Sq-W1BjiW3OioWzzTYEsX1t_VwIguFsNMCCs5NOIURAmds489_mk_YAw&sads=fUfdVJ2oAzd05vklZYl4z2baWfk Hope someone has ideas! Nick Link to comment Share on other sites More sharing options...
cedd Posted April 28, 2015 Share Posted April 28, 2015 So this flicker - did you ever get to the bottom of what was causing it? I'd bet that something electrical, somewhere, was doing something unpleasant. With that in mind you may find that it was RF interference rather than anything coming in on the power supply. An arc or even a dodgy fluorescent can be a wideband source of interference. Link to comment Share on other sites More sharing options...
Nicktaylor Posted April 28, 2015 Author Share Posted April 28, 2015 So this flicker - did you ever get to the bottom of what was causing it? I'd bet that something electrical, somewhere, was doing something unpleasant. With that in mind you may find that it was RF interference rather than anything coming in on the power supply. An arc or even a dodgy fluorescent can be a wideband source of interference. There was a full powercut in Hemel Hempstead three miles away. However it did it again when I was there on Saturday and there had been no obvious fluctuations Link to comment Share on other sites More sharing options...
Stuart91 Posted April 28, 2015 Share Posted April 28, 2015 We had a similar problem yesterday. It turned out to be a single G3 transmitter that was fluctuating wildly, it would spike at different frequencies in sequence. When I spoke to Sennheiser about it the implication I got was that it's a known problem although presumably quite rare. Link to comment Share on other sites More sharing options...
Nicktaylor Posted April 28, 2015 Author Share Posted April 28, 2015 I did wonder if it was TX getting wet from sweat. We had a couple last week who were worse than others. The noise was a low frequency click which you could hear but was not the normal type of feedback. Link to comment Share on other sites More sharing options...
carlskeats Posted April 28, 2015 Share Posted April 28, 2015 Have you done a frequency sweep to check what RF is around your area? Link to comment Share on other sites More sharing options...
Nicktaylor Posted April 28, 2015 Author Share Posted April 28, 2015 Like most people I dont own the equipment to do such a thing and certainly would not have it sitting next to the kit on the off chance! Link to comment Share on other sites More sharing options...
Stuart91 Posted April 28, 2015 Share Posted April 28, 2015 Like most people I dont own the equipment to do such a thing and certainly would not have it sitting next to the kit on the off chance! I bought one of these a while ago. It paid for itself by detecting the fault I mentioned above. We had a job worth well into four figures which was being jeopardised by one misbehaving beltpack and this helped us track it down. Link to comment Share on other sites More sharing options...
Jevans Posted April 28, 2015 Share Posted April 28, 2015 Like most people I dont own the equipment to do such a thing and certainly would not have it sitting next to the kit on the off chance! You can use a ew300/500 G3 receiver as a (basic) tool for spectrum analysis by plugging it into a computer and using WSM to scan the band. Obviously only works on the band the reciever works in but that's what you're interested in anyway... Link to comment Share on other sites More sharing options...
Nicktaylor Posted June 28, 2015 Author Share Posted June 28, 2015 Another show in the same venue. It worked fine until last night when for some reason there was a broad channel 38 sweep through causing a roughly 1 second pulse. The actual sound was like a vinyl click. After 90 minutes of limping along and trying to sort it at 2115 it suddenly stopped! I am wondering if something is generating spurious RF like an electrical system somewhere near and at that time it switched off? Link to comment Share on other sites More sharing options...
Rob_Beech Posted July 1, 2015 Share Posted July 1, 2015 This sounds like a beltpack issue to me. Is this the same equipment as used back in April? There is a known (but very very rare) issue with some g3 packs (maybe handhelds aswell but I've not heard of any) where they do very odd RF things when they get warmer (next to a body etc). I've got one that I keep with the battery cover removed and a huge label on it that I use for demonstration purposes. You get this click like a vinyl click (Great description Nick) every few seconds across quite a broad range, in this case it seems to span at least across all of channel 38. The only difference is that this pack doesn't seem to work properly in itself so YMMV there as you haven't reported a specific component not working. Mine is a 100 series G3 pack but its the same circuit and has been known on others. It could be something entirely different but it sounds very very similar to this issue so that is where my money is. Identifying it? Not going to be easy. Get the packs out, get them warm (get some lights focused on them perhaps, wait until the issue starts and then switch them off one by one until the problem goes away. Rob Link to comment Share on other sites More sharing options...
Nicktaylor Posted July 2, 2015 Author Share Posted July 2, 2015 Thanks for that suggestion. It is mainly the same kit. All tested fine before hand. I worry about the amount of moisture from some of the cast as well! Kit straight to another show where they have eight channels of their own as well so a good test. I have not been running the gear myself beyond first setup, so its has been hard to pin down when running a show which tx might be causing a problem. For example we shut all off at the interval. Switched one on and it happened. Turned that off then the second one on oand it happened at which point we gave up. Started the second half and for no reason at exactly 2115 the problem went away completely. All channels worked fine! I did think ther might be some timed control circuitry in the community centre firing of RF interference which went off at that time. Link to comment Share on other sites More sharing options...
Nicktaylor Posted July 13, 2015 Author Share Posted July 13, 2015 Just done a show in another venue. Twenty chnnnels used and no problems accept a couple of damaged headset mics. This leads me to think there is a a local issue in Kings Langley. There is a police comms mast but I would have thought that far too far a away and anyway why would they radiate on channel 38? Link to comment Share on other sites More sharing options...
paulears Posted July 13, 2015 Share Posted July 13, 2015 The don't radiate on ch 38, but they are below the radio mic allocation at 380MHz-ish. It's possible that a poorly aligned transmitter could have a significant spurious output - and as the Airwave system has various modulation systems, it's feasible an output could scan across the band. I've never heard of it happening, but it's a strong signal, close to you. It could even mix with another system and generate an interference product. As it's gone away, no real problem. CEDD is our expert on radio interference. Link to comment Share on other sites More sharing options...
Nicktaylor Posted July 15, 2015 Author Share Posted July 15, 2015 Thanks Paul. I do want to get to the bottom of it as this venue is my home one so tends to use kit much more than anywhere else so having gear not work there more embarrassing than anything else Link to comment Share on other sites More sharing options...
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