fincaman Posted June 20, 2011 Share Posted June 20, 2011 I have been using Soundlab radio mics for some years with great results. They have 256 Frequencies, I have just finished a show using 8 and they were flawless, they have 17 frequencies that fall within ch 70 does this mean that I will be legal ? What is the general rule as regards separation I always set them as far apart as possible ? I do hope the brand police aren't watching because I have used my Soundlabs side by side with top makes and there was no noticeable difference !!! Link to comment Share on other sites More sharing options...
Bobbsy Posted June 20, 2011 Share Posted June 20, 2011 Probably not totally, I'm afraid. It's not all of Channel 70 that's legal to use, just a small chunk from 863-865 MHz. Those are the outer limits so you bottom and top frequencies have to be above and below these numbers to allow for the FM deviation. Typically you can get about 4 channels in this space though that varies from manufacturer to manufacturer, depending on the quality of their RF filters and their ability to reject intermod from harmonic frequencies. Bob Link to comment Share on other sites More sharing options...
chelgrian Posted June 20, 2011 Share Posted June 20, 2011 It gets to '256' frequencies by considering everything from 851MHz to 865MHz in something like .05MHz steps it seems. The vast majority of these frequencies were never legal to use on a PMSE license anyway which is *not* a continuous license across the spectrum and licensed you for a specific set of 14 frequencies between 854.900 and 861.750. Obviously you can get fixed site licenses for other frequencies but that doesn't sound like it is the case here. The only legal frequencies for these mics to use after then 1st of Jan 2012 are between 863.00 865.00 in which you'll get perhaps 4 mics without intermodulation problems. Sennheiser can get 6 mics (as long as they are all Evolution G3s) into the spectrum due to better RF filtering. Placing frequencies 'as far apart as possible' is not the correct way to avoid intermodulation. The intermod index for a set of frequencies is to do with how the harmonics of each base frequency interact with each other, calculating it is a pain. Sennheiser have features such that you can connect all your receivers together via Ethernet and let the software figure it out. Link to comment Share on other sites More sharing options...
paulears Posted June 20, 2011 Share Posted June 20, 2011 As you're in Spain, does it matter? Spain Largely unregulated. Officially an application form has to be submitted to any 1 of 52 regional offices, at least 20 days before first use. There is a submission fee of 66.45 Euros for the form, and spectrum use is charged on top of that. You must have a Spanish representative with a fiscal number and fiscal address in the country to pay the license fee, which is taken as a tax in Spain. There are some pirate TV stations, particularly around the tourist areas, so you may want to chose your frequencies to avoid broadcast Vision or Sound carriers. First choice would be around UK46 - UK47. Second is UK62 - UK64 which is generally OK in Spain although in theory it is less reliable than UK47. Third choice, UK38 but unproven. UK69 is not reliable. Valencia (2011): Twelve 2020 radio mics from Richmond Film Services on 675.100 to 683.850 MHz and 711.900 to 720.850 MHz. Seville, Cordoba, Tarifa (2007) all had very low shash on UK69 but it worked fine over moderate distances. Costa del Sol - Sotogrande is definitely a bit problematic for UK69, UK62 is better. Barcelona - Inner city is an RF nightmare. Noise, dropouts and poor range on all 16 UK68/69 frequencies on Audio Ltd 2020, worse when in a tall buildings. UK38-40 working well in Madrid. Rest of Spain looking encouraging on UK38-40 too. (Mike Cooper IBSNET 2011) I can't find anything on any license free stuff at all - their home grown system seems 'difficult'. Link to comment Share on other sites More sharing options...
Bobbsy Posted June 21, 2011 Share Posted June 21, 2011 Ooops...I didn't check the OPs location. However, this brings up an interesting thought. The excuse given to us for the loss of Channel 69 (rememember when we were originally told Channel 69 would remain?) was for harmonisation with Europe which is planning to hand over that band to other users. If this is true, the OP may find Channel 69 suddenly full of mobile phones and data. Bob Link to comment Share on other sites More sharing options...
fincaman Posted June 21, 2011 Author Share Posted June 21, 2011 Thanks for your comments, I think I will just carry on as before until someone stops me !!! I still have 17 frequencies between 863.100 MH and 864.900 MHz so I am going to give them a try Link to comment Share on other sites More sharing options...
chelgrian Posted June 21, 2011 Share Posted June 21, 2011 Best I can find is http://www.telecompaper.com/news/spain-to-start-mobile-spectrum-redistribution-in-2011 Which suggests that 800MHz will be allocated to LTE but they haven't decided what they are doing yet. Makes the UK look organised... Link to comment Share on other sites More sharing options...
Bobbsy Posted June 22, 2011 Share Posted June 22, 2011 Thanks for your comments, I think I will just carry on as before until someone stops me !!! I still have 17 frequencies between 863.100 MH and 864.900 MHz so I am going to give them a try You don't have a hope of getting all eight channels between 863 and 865MHz--my betting is that you'll start getting interference above four--it takes really excellent filtering for Sennheiser to even get to six channels. (Just a bit of FM theory: when you set your mic to transmit on 863.1, the "deviation" means that, at peak audio levels, your mic will be transmitting from just over 863.0 MHz up to just under 863.2 MHz--and the filters aren't exact so you have to leave a guard band between these "theoretical" frequencies. This is before we get into the vexed issue of harmonics!) However, from what Paulears found, for the time being you should be legal to venture down into Channel 69 so the "carry on until somebody stops you" seems valid. However, at some point in the future you're likely to find somebody suddenly switching on mobile phone/data masts that spatter all over your lower frequencies. Bob Link to comment Share on other sites More sharing options...
fincaman Posted June 22, 2011 Author Share Posted June 22, 2011 Thanks for your comments, I think I will just carry on as before until someone stops me !!! I still have 17 frequencies between 863.100 MH and 864.900 MHz so I am going to give them a try You don't have a hope of getting all eight channels between 863 and 865MHz--my betting is that you'll start getting interference above four--it takes really excellent filtering for Sennheiser to even get to six channels. (Just a bit of FM theory: when you set your mic to transmit on 863.1, the "deviation" means that, at peak audio levels, your mic will be transmitting from just over 863.0 MHz up to just under 863.2 MHz--and the filters aren't exact so you have to leave a guard band between these "theoretical" frequencies. This is before we get into the vexed issue of harmonics!) However, from what Paulears found, for the time being you should be legal to venture down into Channel 69 so the "carry on until somebody stops you" seems valid. However, at some point in the future you're likely to find somebody suddenly switching on mobile phone/data masts that spatter all over your lower frequencies. Bob Thanks Bob it's an interesting subject I'll do a test as soon as I have time and report back, this will be a great oppertunity to see if my "non Brand" mics get anywhere near Semmheiser. Link to comment Share on other sites More sharing options...
paulears Posted June 22, 2011 Share Posted June 22, 2011 The problem with all FM systems is that the actual deviation is a design feature, and is different for every manufacturer. Two way radio uses a much narrower narrower bandwidth - maybe between 2.5 and 5KHz, with a constricted frequency response suited to speech only. Once you increase the frequency response, and increase the deviation - the perceived quality goes up. Signal to noise ratio is important too - if the deviation is lower, then you'll need more gain at the receiver end, and get an increase in noise. This is why many radio systems use companders - the signal going out is compressed to maximise the available deviation, then expanded at the receiver end. FM radio isn't using the strength of the signal to directly impact on volume that's how AM radio works, so appears to give pretty noise free operation until signal strength drops so far as to suddenly produce those nasty noise bursts we know so well. Cheap radio systems may scrap the compander altogether, and when the signal levels are high, they work quite well, but once levels start to drop, their absence becomes obvious. To squeeze in more channels, it's a simple think to just lower deviation, and ramp up the receiver gain to cope. Result on strong signals again isn't that noticeable, but weak signals cause more grief - AND with a busy band, stand more chance of being 'run over' by signals close in either side. If you have a piece of kit that really does have 17 frequencies in such a small band that others consider cramped for just 4 - then you either have VERY low deviation, or they're not really 17 separate frequencies. Using channel 1 may produce some kind of output on channel 2, and maybe a tiny bit on channel 3. Each one overlapping. As FM systems always have a centre frequency where most of the energy is, at their extreme limits, deviation wise - from the centre frequency, the energy is much less, so your system might let you just tune until they can't be detected, then use them. The other thing could simply be that the 17 channels are just the preset frequency steps - so maybe they are 100KHz steps? That's not the same as channels. Spain's a big country - so you may not have any issues at all - we just don't know yet. As I mentioned up a bit - I'd kind of assumed that unless Orange or whoever put in a mast very close to the venues, many would be able to carry on operating in ch 69 where they are now, without a license - and perhaps unaware anything has changed. However, Sennheiser pointed out that this isn't the problem at all - it's the devices in the pockets of the audience - MUCH closer, and if the base stations are a way away - they suddenly ramp up their power to make the distance, and this could be very nasty - devices that suddenly start to work, after your sound check. Link to comment Share on other sites More sharing options...
Bobbsy Posted June 22, 2011 Share Posted June 22, 2011 I have no doubt that the Soundlab mics TUNE to 17 different frequencies between 863.1 and 864.9. That not far off just putting in a pre-set for frequencies at about 100kHz spacings so people can work out their own frequency plans. However, this doesn't mean that all those frequencies are usable at the same time! One suggestion I meant to put in my previous post: when testing frequencies, don't just turn on all eight mics and see if you get a signal. Find some way of putting a high level audio signal on all at at the same time. The way FM works, the deviation increases as the audio level increases--when things are silent you're more or less putting out a narrow bandwidth carrier but when things get loud is when the interference starts! Bob Link to comment Share on other sites More sharing options...
fincaman Posted June 24, 2011 Author Share Posted June 24, 2011 Hello all sorry but I have been very busy I will get round to trying my mics but I have a lot on, Link to comment Share on other sites More sharing options...
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