norty303 Posted May 9, 2008 Share Posted May 9, 2008 I'm in the process of putting together a rack for a local pub where they have the occassional live night and DJ gigs on the weekend, and we decided that the best thing to do was have a movable rack that could be wheeled in and out of storage as necessary. One of the things that they wanted to be able to do was send a signal to the front of the pub (DJ/bands in back) via the installed system there, rack under the bar. Rather than install a cable and wall box to add another element of complication when setting up I was toying with the idea of putting one of those AV senders in the rack and the receiver end at the bar, so they get signal whenever the system is powered up and in use. Here's some examples of the type of units I'm talking about. http://cpc.farnell.com/jsp/search/browse.j...sender&Ntx= Has anyone used one successfully or has any comments on the effectiveness? Link to comment Share on other sites More sharing options...
bruce Posted May 9, 2008 Share Posted May 9, 2008 Well, since they run on unlicensed frequencies, there's no guarantee that you won't get interference from any adjacent units. Or wifi devices. Or microwave ovens. Or... This could, of course, get very interesting, when the bloke in the flat upstairs decides to replay his home-made porn movies and they get distributed throughout the venue! Stick in a wire. If you really MUST use wireless, think about using an IEM transmitter and a radio mic receiver, on a licensed frequency - at least that way you minimise the chance of interference, and can easily change the freq if necessary. Link to comment Share on other sites More sharing options...
cfmonk Posted May 9, 2008 Share Posted May 9, 2008 AS well as the interference issues I think most of the units in your link are to send simple low quality CCTV / intercoms and the such like. I think they would struggle to send any type of Hi-Fi sound. Chris Link to comment Share on other sites More sharing options...
BenVirgo Posted May 9, 2008 Share Posted May 9, 2008 There great for some purposes but wouldnt trust there reliability in an install Link to comment Share on other sites More sharing options...
norty303 Posted May 10, 2008 Author Share Posted May 10, 2008 Well, since they run on unlicensed frequencies, there's no guarantee that you won't get interference from any adjacent units. Or wifi devices. Or microwave ovens. Or... Ok, so since these are marketed at home users, has anyone ever experienced any of these issues, where microwaves and other such devices are more common than in a pub? Equally, have any home users experienced the neighbours porn? Whilst these are all 'possibilities', what are the real world experiences (e.g. have you got one at home and had problems) I think most of the units in your link are to send simple low quality CCTV / intercoms and the such like At least a number of the units are designed to send video and stereo audio to an alternative point, so that TV, etc can be viewed without the need to run cables. In what way do you think that the signal is going to be degraded? I notice also that they do a unit that sends the signal over electrical cable like the 'Home Plug' ethernet system. If its good enogh for data is it not also reasonable to assume that its good enough for digital audio? The IEM system sounds like a good middle ground, and they're getting cheaper by the day. Link to comment Share on other sites More sharing options...
foh_al Posted May 10, 2008 Share Posted May 10, 2008 Ok, so since these are marketed at home users, has anyone ever experienced any of these issues, where microwaves and other such devices are more common than in a pub? Equally, have any home users experienced the neighbours porn? Whilst these are all 'possibilities', what are the real world experiences (e.g. have you got one at home and had problems) Yup! Had one of these at home. Going in the kitchen whilst the microwave oven was on killed it. Being within a few metres of the cordless phone or its receiver killed it. Nowadays I just walk around with an IEM pack if I want music whilst I cook! Seriously, although the issues I had are very localised, and aren't a problem when you're more than about 15ft from the source of interference, it depends whether or not you're prepared to take the risk. How serious would it be if your music was interrupted by an inconsiderate neighbour's cordless headphones; or a ham radio enthusiast who has yet to learn about harmonics? Personally, I try to avoid wireless audio transmission wherever possible - it's just one more thing that can go wrong. If you really want the freedom of movement, I'd seriously consider a professional system on licensed PMSE frequencies. Having said that, I've just kitted my 5-piece band out with IEMs, and my credit card hurts! Alex Link to comment Share on other sites More sharing options...
Bobbsy Posted May 10, 2008 Share Posted May 10, 2008 There's a truism about wireless: you can spend more than £2,000 on a wireless system that will provide results almost--but not quite--as reliable and good quality as £30 worth of cable. Even besides the potential interference mentioned, wall-warts fall out or overheat, tubby people stand in the way, cheap RF circuits clip too soon, etc. etc. It's not worth it. Install a cable. In fact, pull a small multi because extra tie lines always find a use. Re: your question about the mains-based system, if it feeds computer data successfully, it should do digital audio. However, where are you getting the digital signal with and what are you decoding it with. The description in your OP sounds like an analogue application to me. Bob Link to comment Share on other sites More sharing options...
john-sp Posted May 10, 2008 Share Posted May 10, 2008 As an installer for a number of years, I find that very often the simplest solution is the best all round. A wire is cheaper, but costs slightly more to install properly, using proper containment etc. This would still be MUCH less than a reliable wireless system. However, you don't waste your own time and therefore money returning to solve problems every time -to quote - a tubby person stands in the way and the signal drops. Fit and (hopefully) forget is the best way, and in this case a cabled solution is the way I would go. HTH John G. Link to comment Share on other sites More sharing options...
Matt Riley Posted May 10, 2008 Share Posted May 10, 2008 I was using a cheap 2.4 ghz wireless AV sender to run a live video feed yesterday. During soundcheck it was all fine... got to the actual moment when it was needed and, guess what? picture flickered with vertically scrolling white bars, signal kept dropping out every 2 secs. Moral of the story... should have just run a wire! If you were to install the speakers anyway, then that would dramatically cut setup time, and you could just split the feed to them and the installed BGM rig at the wallbox, meaning then you wouldn't even have to run that 1 extra XLR! M Link to comment Share on other sites More sharing options...
Bobbsy Posted May 10, 2008 Share Posted May 10, 2008 The Farnell site was down for a bit when I first came across this topic but, now that it's back up I checked the spec on the wireless sender. I says it uses a frequency range of 2.4 to 2.4835 GHz. This is smack on the same frequencies as used by 802.11b/g computers so interference between the sender and any wireless networking in the venue is virtually assured. Somebody else mentioned interference from a microwave oven. I thought this spectrum analyser grab of an 850 watt microwave, measured from about six feet away, might confirm that the problem is a real one: http://i27.photobucket.com/albums/c188/Bobbsy/snoop-oven.gif Use cable! Bob Link to comment Share on other sites More sharing options...
bruce Posted May 10, 2008 Share Posted May 10, 2008 The main reason that the 2.4GHz band is "unlicensed" is that until recently none of the broadcasters or telcos wanted it. It's at a resonance (absorption peak) on the water absorption spectrum, and so is pretty useless for long-range links, especially on rainy or foggy days. For exactly the same reason, microwave ovens are tuned to this 2.4GHz resonance to allow them to heat the water. Hence the spectrum Bob posted - microwaves try to dump all their power in the 2.4 band. Of course, it should all stay within the oven... A concurrent post has been automatically merged from this point on. Ok, so since these are marketed at home users, has anyone ever experienced any of these issues, where microwaves and other such devices are more common than in a pub? Equally, have any home users experienced the neighbours porn? Whilst these are all 'possibilities', what are the real world experiences (e.g. have you got one at home and had problems) I've got one of these at home, to allow me to pick up the signal from the sky box through in the bedroom. the signal has to travel less than 10m, through 1 single-brick wall. It works OK most of the time, but is sensitive to positioning. You can tell from the picture when someone stands between the TX and RX. It interfered with my wi-fi, until I stuck both at opposite extremes of the 2.4 band. Never picked up any signals from the neighbours though :) ... I have looked at the RF spectrum in my house with a spectrum analyser, and it backs up Bob's graphs - the spectrum is busy enough at the best of times, with wifi, the video sender and dect phone. Add a microwave to the mix and it's amazing that any of it works! Link to comment Share on other sites More sharing options...
dosxuk Posted May 10, 2008 Share Posted May 10, 2008 The main reason that the 2.4GHz band is "unlicensed" is that until recently none of the broadcasters or telcos wanted it. Not quite true, the 2.4GHz band was being used for short range mobile links in PMSE for decades, however, the Radio Authority (probably when they were gearing up for the change into "flog it all!" OfCom) decided the band wasn't being used sufficiently and opened it up. Pressure from network equipment manufacturers was a major reason for this band being released. This has caused some issues with amount of spectrum available for mobile links on large events, hastening the introduction of digital links - which is where OfCom got the plan to solve their ideas for the DDR. Link to comment Share on other sites More sharing options...
ChrisD Posted May 10, 2008 Share Posted May 10, 2008 Would you be happy to put your name on a system you've been warned by so many different people (and scientfic evidence - thanks Bobsy, very interesting!) won't work? Before I even start any work, I always think, would I buy it? Would I let other people know I've done it? If the answer to either of those questions is no, I'd go for another option. The cable is undoubtedly more monotonous, and potentially messy, but if you do it right, it'll be hard to notice, and as has been suggested, it'll cost way less and sound much better. Just my 2p, but I think this is a no-brainer, now we've got the facts and anecdotes! Link to comment Share on other sites More sharing options...
Jivemaster Posted May 10, 2008 Share Posted May 10, 2008 Another little grief to avoid is the licence approval term that states that most domestic TV senders MUST have a video to go with the audio. L&R audio without a video is a good indicator of a pirate radio station, So you might attract unwanted attention. They use 2.4gHz to send the studio output to a remote and disposible transmitter, - also misfitting the Tx with a high gain antenna. If anyone finds a transmitter on a tower block roof the studio is within 100m but there are no cables to link things! Link to comment Share on other sites More sharing options...
bh00 Posted May 10, 2008 Share Posted May 10, 2008 Surely if you have to run power to the rack, it's easy enough to put a pair of XLRs and spiral wrap them together or something to create a custom multicore? If you wanted to make it more obvious to the person setting it up, you could say fit powercon for the power, and then have outlet panels around the pub with two XLR ins and a powercon. That way you just instruct the persons operating it they can put it anywhere by one of those panels and just plug in the three connectors! Link to comment Share on other sites More sharing options...
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