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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: peter dakin on December 20, 2013, 05:32:36 AM
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What would the best way to combine 4 antennas into one distro, in order to provide coverage for an extremely wide area.
In the past i've used PW Helicals directed at almost 180∘ to each other to ensure mics are being covered by at least one antenna, however I lose any form of diversity, for mics at the far reaches.
Next time around I'd really want to add more helicals, in order to provide mics with true diversity, however the SHURE UA221 splitter/combiners seem a little "delicate" for the job.
Any recommendations would be apreciated.
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Might be running into multi path problems.
http://www.prosoundweb.com/article/addressing_the_myths_of_wireless_system_transmitter_power/live
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Shure Applications Dept. would be a great resource for you. Try giving them a call.
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How big of an area are you actually trying to cover?
Adding more antennas will likely create more trouble than good for you, as the signal coming to each antenna will interfere with the other by just raw combining them.
An alternative would be placing additional receivers tuned to the same frequency to cover each specific area, and then activating the receiver on the mixer closest to the mic user.
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What would the best way to combine 4 antennas into one distro, in order to provide coverage for an extremely wide area.
In the past i've used PW Helicals directed at almost 180∘ to each other to ensure mics are being covered by at least one antenna, however I lose any form of diversity, for mics at the far reaches.
Next time around I'd really want to add more helicals, in order to provide mics with true diversity, however the SHURE UA221 splitter/combiners seem a little "delicate" for the job.
Any recommendations would be apreciated.
When using multiple antennas to cover different zones you have to be very careful to be sure there is essentially no overlap in coverage. You have to take the antenna coverage patterns, terrain, structures, etc into consideration to eliminate covering the same area with 2 antennas on the same side of your diversity system. If you have overlapping coverage you have created an area where you are going to have multipath reception, which can cause dropouts rather than the improved coverage you are looking for.
Once you have taken those things into consideration you need a way to combine the antennas. It is possible to just use passive combiners, but you will have more control with an antenna "mixer" like the PWS DB-1C (http://www.professionalwireless.com/sales/combiners-distribution/db-series-distribution-systems) which lets you combine up to 4 antennas with variable level of each into a mix that is then DA'd to a bunch of outputs to feed various systems. Unfortunately there is no information on their website, and I don't remember the details of how many outputs, but it is often used in large scale situations. You would need 2 of the combiners to maintain diversity, 1 for each antenna system, with each system up to 4 antennas.
If you cannot isolate the coverage of the multiple antennas you are probably better off with an omni antenna, or a very wide coverage directional antenna that can cover the entire area of interest. You can get omni antennas that have a gain higher than zero that achieve the gain by reducing the vertical coverage while maintaining an omni horizontal pattern.
Mac
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What would the best way to combine 4 antennas into one distro, in order to provide coverage for an extremely wide area.
In the past i've used PW Helicals directed at almost 180∘ to each other to ensure mics are being covered by at least one antenna, however I lose any form of diversity, for mics at the far reaches.
Next time around I'd really want to add more helicals, in order to provide mics with true diversity, however the SHURE UA221 splitter/combiners seem a little "delicate" for the job.
Any recommendations would be apreciated.
To combine 2 sets of antennas the UA221 or Sennheiser ASP 212 is fine. The passive loss in the combiner can be compensated by cranking the antenna boosters up 3 db.
The expensive solution is http://www.wisycom.com/www3/products/product/mat243-mat283
As other have said, place the antennas to get the minimum overlap between the pairs.
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On the other option of two receivers would using something like the shure scm810 smart mixer be able to detect the level of the receivers and activate the best signal. Also providing the fail over with automatic switching.
I understand that most of the technology is detected in the receiver for the best RF signal.
With the antennae is it possible to put up a 10 or 20 foot mast and a pair of yagis in opposite directions, pointing down near the back of the crowd? (prefer 20 foot)
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When using multiple antennas to cover different zones you have to be very careful to be sure there is essentially no overlap in coverage.
Would 4 directional antennas pointing out covering 4 quadrants (at 10-2-4 and 8 o'clock) with an A_B_A_B pattern and the use of the Shure passive combiners for the 2 A and 2 B antennas work?
That way, as mics "move" around the outlying coverage area, there would always be an A-B or B-A diversity available.
The A and B antennas would be "back to back" so they would not receive the same signal as long as the transmitters don't get too close to the receivers.
Of course, this doesn't take into account any reflected signals.
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Would 4 directional antennas pointing out covering 4 quadrants (at 10-2-4 and 8 o'clock) with an A_B_A_B pattern and the use of the Shure passive combiners for the 2 A and 2 B antennas work?
That way, as mics "move" around the outlying coverage area, there would always be an A-B or B-A diversity available.
The A and B antennas would be "back to back" so they would not receive the same signal as long as the transmitters don't get too close to the receivers.
Of course, this doesn't take into account any reflected signals.
If you want 360º coverage use a couple of omni antennas as a diversity pair. Your example gives up all diversity in favor of coverage. The ideal is to have full coverage and diversity, going to either extreme (diversity or coverage) just to use directional antennas does not seem like a step in the right direction.
If you are trying to solve a particular coverage problem, draw a map so we can see what you are trying to do.
Mac
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If you want 360º coverage use a couple of omni antennas as a diversity pair. Your example gives up all diversity in favor of coverage. The ideal is to have full coverage and diversity, going to either extreme (diversity or coverage) just to use directional antennas does not seem like a step in the right direction.
If you are trying to solve a particular coverage problem, draw a map so we can see what you are trying to do.
Mac
I was responding to the OPs question relating to a wide area. I'm figuring the omnis didn't work out as he is using directional antennas.
He is trying to cover a large area and said he used only 2 directional antennas back to back and lost diversity.
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What would the best way to combine 4 antennas into one distro, in order to provide coverage for an extremely wide area.
I have been quite successful in using multiple RX and TX antennas in one venue. To keep the Diversity you need to cover each area with the 2 channels of antennas and the antennas need to be at lease 6-30' apart - say on each side of the stage.
Multiple RX antennas in one zone do not cause dropouts, it only increases the signal so there is no need to be particularly careful in overlapping the coverage. For transmit systems minimum overlap is desirable but also has little bad effect.
The entire trick is managing the levels from your antennas. Long Coax introduces loss and in many locations you can use an amplified +10dB antenna to make up. In Hi RF level areas, though, amplified antennas cannot be used at all because they overload. Areas such as 34th street near Macy's In NYC which is less than a mile from the Empire State Building TV antennas.
Splitters and combiners need to be best quality with minimum loss. My favorites come from Mini circuits. A 1X 2 splitter at 600 mHz has about 3.5 dB loss.
Another terrific new tool is RF over fiber. It is not for the novice to use and requires a lot of careful RF level wide band measurements covering all the concurrent carriers which will be carried on the fiber. The advantage is no loss!
Here are a layout for multiple antenna system transmit and RX system which was not for Mics nor was diversity. Same could be applied to a diversity system but double.
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Pete, thanks for posting that. Fantastic info!
I have been quite successful in using multiple RX and TX antennas in one venue. To keep the Diversity you need to cover each area with the 2 channels of antennas and the antennas need to be at lease 6-30' apart - say on each side of the stage.
Multiple RX antennas in one zone do not cause dropouts, it only increases the signal so there is no need to be particularly careful in overlapping the coverage. For transmit systems minimum overlap is desirable but also has little bad effect.
The entire trick is managing the levels from your antennas. Long Coax introduces loss and in many locations you can use an amplified +10dB antenna to make up. In Hi RF level areas, though, amplified antennas cannot be used at all because they overload. Areas such as 34th street near Macy's In NYC which is less than a mile from the Empire State Building TV antennas.
Splitters and combiners need to be best quality with minimum loss. My favorites come from Mini circuits. A 1X 2 splitter at 600 mHz has about 3.5 dB loss.
Another terrific new tool is RF over fiber. It is not for the novice to use and requires a lot of careful RF level wide band measurements covering all the concurrent carriers which will be carried on the fiber. The advantage is no loss!
Here are a layout for multiple antenna system transmit and RX system which was not for Mics nor was diversity. Same could be applied to a diversity system but double.
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How big of an area are you actually trying to cover?
Adding more antennas will likely create more trouble than good for you, as the signal coming to each antenna will interfere with the other by just raw combining them.
An alternative would be placing additional receivers tuned to the same frequency to cover each specific area, and then activating the receiver on the mixer closest to the mic user.
Area was 90-140m wide and 10m-15m deep. However the stage area was in the centre and only real logical position for antenna's.
This was a quick fire Q&A event, with 32 romaing mics, for about 3000 people on tiered seating. There would be no time to decided which receiver to go wth, sadly.
Giving Shure a call isn't a bad idea.
Pete Erskine, sounds interesting, will investigate into your suggestions.
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90-140m x 10-15m doesn't seem to big to me.
If you can put your antennae somewhere with line of sight to all (at least most) of the room, then I'd be tempted to up your HH Tx to 50mW/100mW and go from there.
Alternatively, 2 pairs of Rx antennae (LPDA-type) at each end of the long space, over fibre (to minimise RF loss on cabling), combined back at the receivers to feed your distributors A and B antenna inputs.
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Pete, could you clarify the use of more than 1 RX antenna in the same coverage area?
I was under the (mistaken?)impression that if 2 antennas (that combine at the same receiver) were used over the same area, there might be phase cancellations possible.
However, in a diversity system , this might not be a problem.
The reason I ask is that I have a job that requires coverage of a hockey rink but I have to have the antennas down below the edge of the boards. (no other option) in a fairly congested RF environment.
A diversity pair at each end might give me the results I need but I have been reluctant to try.
Any insights would be appreciated.
Also, could you give the model of equipment to do Rf over Fibre?
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Pete, could you clarify the use of more than 1 RX antenna in the same coverage area?
I was under the (mistaken?)impression that if 2 antennas (that combine at the same receiver) were used over the same area, there might be phase cancellations possible.
However, in a diversity system , this might not be a problem.
The reason I ask is that I have a job that requires coverage of a hockey rink but I have to have the antennas down below the edge of the boards. (no other option) in a fairly congested RF environment.
A diversity pair at each end might give me the results I need but I have been reluctant to try.
Any insights would be appreciated.
Also, could you give the model of equipment to do Rf over Fibre?
There is no issue with using multiple RX antennas in same area. Get you antennas high enough for good line of sight. Covering a football field size area from one side is no problem if your frequencies are clean. If you want put the 2 diversity antennas on each end of the fiels (2 on each channel) Use +10 dB antennas on the cables which are over 200' long.
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There is no issue with using multiple RX antennas in same area. Get you antennas high enough for good line of sight. Covering a football field size area from one side is no problem if your frequencies are clean. If you want put the 2 diversity antennas on each end of the fiels (2 on each channel) Use +10 dB antennas on the cables which are over 200' long.
Thanks for the info.
The particular hockey rink application doesn't allow for any antennas in any kind of line of sight do I had to work out something.
I got pretty good results with log periodics against the boards at one end but I think antennas at the other end as well would be helpful.
Dodgers stadium was absolutely jammed with DTV signals so it was a real trick to find some clean spaces!
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The particular hockey rink application doesn't allow for any antennas in any kind of line of sight d
Tell them that that is unacceptable. No line of sight - NO RF. They wouldn't put that restriction on the lighting equipment - same is true for Antennas. Stand your ground.
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On the other option of two receivers would using something like the shure scm810 smart mixer be able to detect the level of the receivers and activate the best signal. Also providing the fail over with automatic switching.
I have seen this work very well. It was used for a casino where they wanted 1 mic to work everywhere. Not sure how well it would work for multiple mics in different coverage areas.
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Also, could you give the model of equipment to do Rf over Fibre?
RF over fiber is terrific but needs a lot more engineering to make it work well. First is determining the transmit RF level to put into the hardware. If you are only sending 1 carrier it's easy - measure the RF power and pad it down to 0dBm. If you are using multiple carriers you need to set your RF Power meter to include the entire bandwidth and measure with all carriers on at the same time and pad it down to 0 dBm.
Simple Spectrum analyzers will not work. A R&S FSH3 will measure power levels.
The automatic level control compensates for some level differences in the RF levels.
RX Fiber is easier since unless your Walkie talkie or your wireless mic is really close next to the RX antenna you wont be getting over 0dBm.
Here is a nice but expensive package from Riedel Communications. The fiber cable between the fiber TX and fiber RX needs to be single mode Angle Polished Connector or APC. Normal Single mode will not work very well if it has flat polished connectors.
RF over fiber usage PDF (https://dl.dropboxusercontent.com/u/6029531/DS_RF-over-Fiber_EN.pdf)
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Tell them that that is unacceptable. No line of sight - NO RF. They wouldn't put that restriction on the lighting equipment - same is true for Antennas. Stand your ground.
I hear you but sometimes the situation simply doesn't allow me to get what I want or should have. :(
We were the low guys on the production totem pole. Down the road, I may be able to push back a bit harder.
Overall, the antennas at board level worked out OK due to the fact that there was a limited number of people on the ice.
A second set, at the other end, might allow me to drop TX power down from 100mw as well.
It would be a cable length consideration then.
The RF over fibre does look like it is a bit tricky and probably out of my budget!
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There are lots and lots of people who make RF over fibre equipment. Plenty to choose from.
The issue, in our application, is finding a system that is nice and neat and lends itself to radio mic usage.
Sennheiser now make a system which I can't find on their site, but is clearly shown here: http://www.gasolinemedia.com/sennheisers-high-fibre-diet.htm
I've used this very successfully, and it works well because its packaged perfectly for our environment.
Its cheaper than the riedel system
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Sennheiser now make a system which I can't find on their site, but is clearly shown here: http://www.gasolinemedia.com/sennheisers-high-fibre-diet.htm
It's not Senheiser but a related company who has packaged this. Not designed for US.
Google Rf over fiber and see others.
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Here is one that I don't think costs too much. They also have some interesting antenna options.
http://www.rfvenue.com/rf-optix-fiber-optic-conversion-system
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Here is one that I don't think costs too much. They also have some interesting antenna options.
http://www.rfvenue.com/rf-optix-fiber-optic-conversion-system
This looks like a good option.
I asked for a price and will let you know what I find out
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It's not Sennheiser but a related company who has packaged this. Not designed for US.
Care to elaborate? What specifically makes it not US friendly?
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Care to elaborate? What specifically makes it not US friendly?
240 volt only which doesn't mean it cant be used, just that it wasn't friendly.
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240 volt only
US don't have transformers? 1:2 Step up transformer and your sorted... If you want to go new tech I am pretty sure someone has created a switch mode supply that does the same for you...
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This looks like a good option.
I asked for a price and will let you know what I find out
http://www.rfvenue.com/rf-optix-fiber-optic-conversion-system (http://www.rfvenue.com/rf-optix-fiber-optic-conversion-system)
Quite reasonable price. The RF Optix kit will have a MAP of $699 USD.
Fiber must use FC/APC (angle polished connectors) which eliminates regular fiber cables.
Here is their response and product info
Hello Keith and Peter!
I saw the discussion thread on PSW and also your pricing/info requests on RFvenue.com and thought I’d get back to you with some info on our soon to be released RF to fiber conversion platform.
The "RF Optix" kit consists of (1) optical transmitter (placed at antenna end) and (1) optical receiver unit placed at the rack or other home run position. It is designed for use under 1 GHz and for best possible performance across the UHF band where most RF Venue customers’ IEMs and wireless microphones operate.
I should note that special attention has been paid to the noise floor and headroom of the system and that it is a very basic simplex design, a wider range of capabilities and configurations are planned for the future..
Instead of including an onboard amplifier in the system as is commonly done to makeup the relatively high insertion loss associated with any fiber optic system, we’re opting to offer an in-line amplifier as an option, since most users report greater proximity to the wireless mic transmitters (and greater signal to noise) as one of the benefits of the RF Optix system. The total loss would translate to about a 200’ run of our low loss mini RG8X coax, which is around the length where temporary or permanent coax applications become a real nuisance. E.g. it might not make a lot of sense to use the Optix system for a 50’ extension project, but for 150+ ft the cost and transmission line loss of the coax start to offer diminishing returns. This is especially true for plenum rated coax required for in-wall or in-ceiling permanent installs. I got a quote on a long run of plenum LMR400 the other day and nearly fell out of my chair.
The system is currently in production and should be shipping over the next few weeks. As such the final specs have not been published but will be soon. You can find those on the update RF Optix product page when it launches.
The transmitter and receiver units feature screw on FC connectors, and the system is 9/125 single mode simplex. For a diversity wireless microphone application, a pair of RF Optix units would be required. A screw on 9V power supply is included for either end of the link, and we are currently testing out a really cool rechargeable battery that could power two transmitter units at the antenna end.
Best Regards,
Chris Regan
RF Venue
72 Nickerson Road
Ashland, MA 01721
tel. 339-309-0218
@RFvenue
http://www.RFvenue.com
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Quite reasonable price. The RF Optix kit will have a MAP of $699 USD.
Considering the additional price of the fibre optic cable and considering the price of good quality coax, it looks like runs under about 250'-300' would not make economic sense.
Perhaps from an RF loss standpoint, it might.
Thoughts Pete?
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Considering the additional price of the fibre optic cable and considering the price of good quality coax, it looks like runs under about 250'-300' would not make economic sense.
Perhaps from an RF loss standpoint, it might.
Thoughts Pete?
RF over fiber is not about saving money. It is an expensive solution. It is about getting useful RF signal over long distances, and in difficult RF situations. When you need RF over fiber, you really need it. If you don't need it, use low loss coax like LMR-400.
Mac
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Considering the additional price of the fibre optic cable and considering the price of good quality coax, it looks like runs under about 250'-300' would not make economic sense.
Perhaps from an RF loss standpoint, it might.
Thoughts Pete?
Coax LMR-400 (non Plenum) is about $220 for 200' (Plenum cable is closer to $6 per foot)
200' of One core of a single mode plenum fiber with FC/APC connectors is less than $60
http://www.fiber.com/catalog/product_info.php?products_id=6342{1}1{2}60 (http://www.fiber.com/catalog/product_info.php?products_id=6342{1}1{2}60)
Your extra cost comes with the hardware but with no loss compared to the Coax.
Just out of convenience I wouldn't use fiber until I was longer than 200' it's just simpler and if I can put a +10dB RX antenna at the beginning I mostly make up the loss.
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RF over fiber is not about saving money. It is an expensive solution. It is about getting useful RF signal over long distances, and in difficult RF situations. When you need RF over fiber, you really need it. If you don't need it, use low loss coax like LMR-400.
Mac
Mac, when RF, coms and non-copper distribution become topics, I'm all ears (pun intended).
Doing a bit of internet searching I've determined that I need RF/optical remediation. Is there a source of foundational knowledge? My 35 year old mobile com RF experience is incredibly last century...
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Mac, when RF, coms and non-copper distribution become topics, I'm all ears (pun intended).
Doing a bit of internet searching I've determined that I need RF/optical remediation. Is there a source of foundational knowledge? My 35 year old mobile com RF experience is incredibly last century...
Very technical article http://alexandria.tue.nl/extra2/200512106.pdf (http://alexandria.tue.nl/extra2/200512106.pdf)
Very simplistic explanation http://www.finisar.com/sites/default/files/pdf/RF-over-Fiber%20brochure%207_2013%20V1.pdf (http://www.finisar.com/sites/default/files/pdf/RF-over-Fiber%20brochure%207_2013%20V1.pdf)
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My systems tend, these days, to have short antenna cables and have the relevant Tx/Rx devices closer to the antenna. I then send control and audio data over fibre.
On bigger jobs, this often works out more cost effective since I can send a whole bunch of data down a single (or redundant pair) of tactical fibres. And in these cases, you often get to the point where the cost of the fibre and endpoints is cheaper than the analog equivalent, even at shorter distances.
Not to mention you can actually end up with the rental house dream of having completely interchangeable cable systems. One cable that can be an audio multicore, a pair of video feeds, a data connection, or all of the above, etc...
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There are lots and lots of people who make RF over fibre equipment. Plenty to choose from.
The issue, in our application, is finding a system that is nice and neat and lends itself to radio mic usage.
Sennheiser now make a system which I can't find on their site, but is clearly shown here: http://www.gasolinemedia.com/sennheisers-high-fibre-diet.htm
I've used this very successfully, and it works well because its packaged perfectly for our environment.
Its cheaper than the riedel system
I just got my CATV 4 mW RF Optical Transmitter and Receiver from http://questtel.com/item.php?id=2 works perfectly in many buildings
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I just got my CATV 4 mW RF Optical Transmitter and Receiver
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Mac