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Author Topic: IEM and DAS  (Read 809 times)

Gian Luca Cavalliini

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IEM and DAS
« on: May 25, 2018, 04:25:27 am »

Hi all,
made some tests yesterday with two LPDA trasmitting same signal from Shure Combiner PA421A in a little arena (4 PSM 900). Out of combiner to passive splitter to 2 RG58 (3m) connected to 2 Wisycom passive LPDA pointed opposite ways (2 meter apart). Result: better overall signal stability in the far corner of location.
Question: is that usually done in big large spaces also without wall significant RF separation between zones?
I have to do a big show with request for more than 70m large IEM talent moves, and only place where I can put Helix antenna is in the back of the stage, do you great RF guru think it should be a good idea to use two Helix, pointed to SL and SR, maybe with a RF booster (10 dB) to compensate split and cable loss (about 30 meters RG213)?
Thanx in advance!
GLuca
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Jordan Wolf

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Re: IEM and DAS
« Reply #1 on: May 25, 2018, 01:03:03 pm »

Would something like this simplify your setup?
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Gian Luca Cavalliini

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Re: IEM and DAS
« Reply #2 on: May 25, 2018, 03:09:50 pm »

Would something like this simplify your setup?
Hi Jordan thanx for response! I know bidirectional LPDA from PW, maybe not for this case but it's one of the thing in my wish list :-)
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Jean-Pierre Coetzee

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Re: IEM and DAS
« Reply #3 on: May 26, 2018, 01:48:48 am »

Do you really need the antenna gain from a directional antenna? Why not just go with 2 dipoles?
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Gian Luca Cavalliini

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Re: IEM and DAS
« Reply #4 on: May 26, 2018, 02:43:52 am »

Do you really need the antenna gain from a directional antenna? Why not just go with 2 dipoles?

Thanx Jean-Pierre for contributing!
Ideal maybe could be one helix (about 50/60m to "cover") AND one half dipole, antenna position will not be in the center of stage (public is 360 degrees, so I need to put at least one of them on a tower). But I'm not sure that could be a good idea, made that in receiving application, never did TRANSMITTING in the same open space. I don't think two dipoles give me enough S/N when talents go far and turn themself with bodypack in the opposite from antenna (18 dB additional loss). The place itself ISN'T RF quiet and I have other 16 IEM (center stage, with "normal" combining + antenna system) and 18 wireless transmitter, 60.000 people all around WITH WIRELESS BRACELET (433 MHz, but don't know transmission power), etc..

PSM1000 are 50mw, 10dB booster is just compensation for long wiring and passive split (and maybe not enough, antenna cable is about 5.5 dB loss every 20m at band used, I think I will need AT LEAST 30m, maybe 40, monitor world is UNDER the stage.

Ah: tons of led lighting and led FLOOR! Made some tests, looked good, but I know EMI will change with colors and other settings and can't be completely sure about them...

Uh. Going to take another coffee... ;-)
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Jordan Wolf

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Re: IEM and DAS
« Reply #5 on: May 26, 2018, 10:42:49 am »

Uh. Going to take another coffee... ;-)
Sounds like you’ve got your work cut out for you! Is this a one-off or a repeating gig?

I sounds to me like you need to have another zone of coverage in the far field.

Are there any delay stacks or hangs you can mount an antenna to? RF over Fiber might work if coax runs are too lengthy and impractical.
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Gian Luca Cavalliini

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Re: IEM and DAS
« Reply #6 on: May 26, 2018, 03:01:38 pm »

Sounds like you’ve got your work cut out for you! Is this a one-off or a repeating gig?

I sounds to me like you need to have another zone of coverage in the far field.

Are there any delay stacks or hangs you can mount an antenna to? RF over Fiber might work if coax runs are too lengthy and impractical.

Hi Jordan!
One-off show

Yes, I'd like to have two zone of coverage just for the two main artists that will go outside the stage (two catwalks, SL and SR). Not a problem with handelds, but first time with IEMs in a stadium...
Audience is 360 degrees, all around, no delay tower.

RF over Fiber was my first thought to put antennas under the rooftop, but when i saw the light plot I changed idea...  ::)
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Henry Cohen

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Re: IEM and DAS
« Reply #7 on: May 27, 2018, 07:30:55 pm »

made some tests yesterday with two LPDA trasmitting same signal from Shure Combiner PA421A in a little arena (4 PSM 900). Out of combiner to passive splitter to 2 RG58 (3m) connected to 2 Wisycom passive LPDA pointed opposite ways (2 meter apart). Result: better overall signal stability in the far corner of location.
Question: is that usually done in big large spaces also without wall significant RF separation between zones?
I have to do a big show with request for more than 70m large IEM talent moves, and only place where I can put Helix antenna is in the back of the stage, do you great RF guru think it should be a good idea to use two Helix, pointed to SL and SR, maybe with a RF booster (10 dB) to compensate split and cable loss (about 30 meters RG213)?

Having multiple TX antennas [when needed] to provide the necessary coverage is a fairly common practice. The key is to find the best compromise between minimizing overlapping coverage area, yet provide strong/stable and continuous coverage throughout the desired area(s). This can be tricky to obtain and generally requires a number of walk tests and repositioning of antennas to get the best performance.

I would strongly suggest sending the RG58 and the RG213 to the recycler and replace it with double shielded (braid over foil) low loss coax, such as Times Microwave LMR series, PWS S9046, Belden 9913F7, Belden RF240 / RF400, or Eupen EC series. Not only will there be less coaxial losses, but less RF radiation from the coax possibly affecting other audio equipment, desensing receivers, or having physically adjacent transmitters causing additional IM products due to the other carriers back feeding into the final stages [internally].
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Gian Luca Cavalliini

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Re: IEM and DAS
« Reply #8 on: May 28, 2018, 02:22:36 am »

Having multiple TX antennas [when needed] to provide the necessary coverage is a fairly common practice. The key is to find the best compromise between minimizing overlapping coverage area, yet provide strong/stable and continuous coverage throughout the desired area(s). This can be tricky to obtain and generally requires a number of walk tests and repositioning of antennas to get the best performance.

I would strongly suggest sending the RG58 and the RG213 to the recycler and replace it with double shielded (braid over foil) low loss coax, such as Times Microwave LMR series, PWS S9046, Belden 9913F7, Belden RF240 / RF400, or Eupen EC series. Not only will there be less coaxial losses, but less RF radiation from the coax possibly affecting other audio equipment, desensing receivers, or having physically adjacent transmitters causing additional IM products due to the other carriers back feeding into the final stages [internally].

Thanx Henry, I really appreciate your suggestion  :)
I asked for LMR 400 but RG213 is was rental company wants to give me. I have a meeting today, I'll report what you wrote. I'm starting to think in Italy we're missing a company specialised in RF for shows, it's really hard to find lot of items which seems to be pretty important...
Thanx again to all active contributors of this wonderful forum!

GLuca
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Diogo Nunes Pereira

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Re: IEM and DAS
« Reply #9 on: May 28, 2018, 04:49:19 pm »

Messi and Paoloni (www.messi.it) is an Italian manufacturer of coax cable, well respected among the ham radio crowd.

 Among their product range there is plenty of double shielded coax cable with good specifications. Maybe you can convince your provider to get some of their cable and it being an Italian product might not be difficult to source.


Diogo

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Gian Luca Cavalliini

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Re: IEM and DAS
« Reply #10 on: May 29, 2018, 06:38:09 pm »

Messi and Paoloni (www.messi.it) is an Italian manufacturer of coax cable, well respected among the ham radio crowd.

 Among their product range there is plenty of double shielded coax cable with good specifications. Maybe you can convince your provider to get some of their cable and it being an Italian product might not be difficult to source.


Thanx Diogo! Really appreciate EVERY advice. 30 years of monitor engineering on my shoulder, but just a few years with not easy RF tasks. I study every day as a (good) child, but more I learn, more I need to know...  ;D

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Ike Zimbel

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Re: IEM and DAS
« Reply #11 on: June 05, 2018, 05:57:55 am »

Thanx Henry, I really appreciate your suggestion  :)
I asked for LMR 400 but RG213 is was rental company wants to give me. I have a meeting today, I'll report what you wrote. I'm starting to think in Italy we're missing a company specialised in RF for shows, it's really hard to find lot of items which seems to be pretty important...
Thanx again to all active contributors of this wonderful forum!

GLuca
Wisycom is from Italy. They have some very innovative RF products. https://wisycom.com/about-us/ No one has mentioned this, but amplifying your IEM signal after the combiners is pretty much a non-starter as it will lead to far more problems than it solves. I'm sure Henry can provide more detail on that subject.
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Gian Luca Cavalliini

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Re: IEM and DAS
« Reply #12 on: June 05, 2018, 06:54:08 pm »

Wisycom is from Italy. They have some very innovative RF products. https://wisycom.com/about-us/

Hi Ike,
I know very well Wisycom, I use handeld MRK with Shoeps capsule from 7 years with one of the bands I usually work as a mon eng, great products. Believe it or not... Wisycom in Italy is not so commonly used in live concerts, I know it's a shame but they don't seems too much interested in italian live market (not so rich, actually...).


No one has mentioned this, but amplifying your IEM signal after the combiners is pretty much a non-starter as it will lead to far more problems than it solves. I'm sure Henry can provide more detail on that subject.

Oh... My idea was to bring back about 10 dB of loss for very long wiring and passive split of the far antenna.


Anyway: the shows I was worried about was some days ago, 75.000 people, 90m x 80m area to cover with 16 IEMs and 24 transmitters (plus opening act, about 8 more frequencies). All went good, no necessity to use RF switch or other "strange" things. But I have some new questions for all of you great RF gurus... I'll go in another thread.

BTW: The show was in Milan, Meazza Stadium (San Siro). I can post here or just on Pete's database) the scans if you want...

BTW 2: No problems also from Google led wireless controlled bracelets, every change of colours was a brief impulse at different frequency but always between 433 and 434 MHz, strong intensity (they used a set of Yagi antennas pointed everywere, located near FOH) but not problematic for me.

Thanx & bye
GLuca
« Last Edit: June 05, 2018, 06:56:22 pm by Gian Luca Cavalliini »
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