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Author Topic: Combining Wireless Combiners  (Read 377 times)

David Lim

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Combining Wireless Combiners
« on: May 09, 2018, 02:54:39 pm »

Hey all,

I just took over some monitor duties and inherited a wireless IEM rack with 2 Sennheiser combiners, an AC3 and an AC 2. The previous engineers had both combiners running into a Y adapter before sending to a helical antenna. My question is: should I be worried about this configuration? I'm still learning the ins and outs of wireless tech.

Thanks!
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DavidL

Tim Weaver

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Re: Combining Wireless Combiners
« Reply #1 on: May 09, 2018, 02:58:58 pm »

I won't pretend to know the answer, but I would be inclined to sell the Helical and buy 2 paddles. Use 1 paddle and combiner for all the backline musicians, and another paddle and combiner for the front line muso's. This keeps your recievers in a more or less straight line in front of the paddle, and keeps the paddles far enough apart so they can work well.
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Diogo Nunes Pereira

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Re: Combining Wireless Combiners
« Reply #2 on: May 09, 2018, 04:41:01 pm »

Hey all,

I just took over some monitor duties and inherited a wireless IEM rack with 2 Sennheiser combiners, an AC3 and an AC 2. The previous engineers had both combiners running into a Y adapter before sending to a helical antenna. My question is: should I be worried about this configuration? I'm still learning the ins and outs of wireless tech.

Thanks!

Depending on the nature of what you call "Y adapter"... maybe you should be worried.

Not so much if that adapter is a passive 50-ohm RF combiner. Something like this:

https://www.minicircuits.com/WebStore/dashboard.html?model=ZAPD-21-N%2B

should be fine if your OK to lose 3db for each carrier you need to get on-stage.
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David Lim

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Re: Combining Wireless Combiners
« Reply #3 on: May 09, 2018, 04:46:36 pm »

Depending on the nature of what you call "Y adapter"... maybe you should be worried.

Not so much if that adapter is a passive 50-ohm RF combiner. Something like this:

https://www.minicircuits.com/WebStore/dashboard.html?model=ZAPD-21-N%2B

should be fine if your OK to lose 3db for each carrier you need to get on-stage.

Nope.

Just a little T-Adaptor, like this, but I don't know impedance: https://www.amazon.com/BNC-T-Adapter-3-Female/dp/B0002ZPFHQ
« Last Edit: May 11, 2018, 01:23:04 am by David Lim »
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DavidL

Jason Glass

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Re: Combining Wireless Combiners
« Reply #4 on: May 09, 2018, 05:41:40 pm »

Nope.

Just a little T-Adaptor, like this, but I don't know resistance: https://www.amazon.com/BNC-T-Adapter-3-Female/dp/B0002ZPFHQ
Those are staggeringly harmful to your signal strength. A proper passive combiner such as Diogo suggested is appropriate, if your system can afford the inherent 3dB combiner loss

Sent from my Nexus 5 using Tapatalk

David Lim

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Re: Combining Wireless Combiners
« Reply #5 on: May 09, 2018, 05:48:41 pm »

Those are staggeringly harmful to your signal strength. A proper passive combiner such as Diogo suggested is appropriate, if your system can afford the inherent 3dB combiner loss

I think I can afford a 3dB loss, I'd expect that, but just curious, what kind of loss are we talking about with that T? Again for reference, it's an AC3 and AC2 combiner into a helical, combined at the T.

Thanks!!
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DavidL

Jason Glass

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Re: Combining Wireless Combiners
« Reply #6 on: May 09, 2018, 08:22:35 pm »

I think I can afford a 3dB loss, I'd expect that, but just curious, what kind of loss are we talking about with that T? Again for reference, it's an AC3 and AC2 combiner into a helical, combined at the T.

Thanks!!

It's frequency dependent, and also related to the "electrical length" of your cables and frequency wavelength, but the loss suffered by inserting one of those things can theoretically approach 100% in certain circumstances. That would be bad, indeed, for your application. What's more concerning is that almost all of that lost power reflects straight back into its source, contributing greatly to increased emission of intermodulation products (RF noise).

Regarding affording 3dB of loss, that's half of your power output. When you're combining G2's and G3's, you have a maximum output of 30mW. That's not a whole lot of extra power to overcome cable losses, free space loss, and the fact that G2's are antiquated and barely function by comparison to current systems' performance, and they need all the help they can get to sound halfway decent (again, by comparison). I'm not saying that they have no worth, because they can satisfy some users and make you some $. But they do require much attention and are not very robust in the high RF noise environments in which we must often operate. Inserting passive lossy components downstream from them rarely has a reliably positive result.

On the bright side, using helical antennas with most IEMs, including the previously maligned G2, almost always increases their RF range and reliability, at least a little, when deployed properly. They typically have 11 dB to 14 dB of on-axis gain, which can make up for the losses that I mentioned above. 3 dB of that is usually lost in "polarization mismatch loss" but it eliminates the wildly varying levels of a paddle's (LPDA) potential pol mismatch loss (0 dB to infinite dB). Considering that a typical PCB paddle has 5 dB to 6 dB gain before losses are considered, the helical almost always beats it in total performance.

Bottom line is that your lowest cost option for best case scenario, without replacing your G2 and G3 with much more expensive systems, is to lose the 2-way combiner and deploy a 2nd helical.

Sent from my Nexus 5 using Tapatalk
« Last Edit: May 09, 2018, 08:30:40 pm by Jason Glass »
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Don Boomer

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Re: Combining Wireless Combiners
« Reply #7 on: May 09, 2018, 08:24:42 pm »

Nope.

Just a little T-Adaptor, like this, but I don't know resistance: https://www.amazon.com/BNC-T-Adapter-3-Female/dp/B0002ZPFHQ

Shoot that thing!
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Don Boomer
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David Lim

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Re: Combining Wireless Combiners
« Reply #8 on: May 10, 2018, 12:32:21 pm »

Shoot that thing!

Haha itís done for!

Thanks all, this clears up a lot, and confirms what I thought was the case but didnít understand. Really appreciate your help!
« Last Edit: May 11, 2018, 01:24:51 am by David Lim »
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DavidL

Scott Helmke

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Re: Combining Wireless Combiners
« Reply #9 on: May 10, 2018, 12:54:18 pm »

We've had absolutely no complaints about these little 2:1 thingies:
http://www.professionalwireless.com/product/2-way-high-power-splittercombiner/
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