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Author Topic: Positioning of Omni antenna's  (Read 1994 times)

Tom Simenauer

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Positioning of Omni antenna's
« on: August 24, 2017, 06:38:28 am »

Hi.
The venue:

Old church, 40m by 30m with a 30m ceiling. 3 wireless mics, roaming 30 x 35 meters.

Different advice i have had:

 a knowledgeable guy at a well respected audio company here in the UK suggested i place the 2 Sennheiser A1031U omni antenna's close together like around 3 to 5 feet apart.

I have been told by a few people on forums and in retail shops that my plan to have them either side of the stage in the church i do the sound for would be good practice. They would be about 10 meters apart.

I am new to all of this. So i don't know.
Please advice, as this will also determine the length of cable i will need.
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Keith Broughton

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Re: Positioning of Omni antenna's
« Reply #1 on: August 24, 2017, 06:52:23 am »

Should work fine but remember to buy good quality, low loss coax antenna cable.
Getting all this hardware together is fine but co-ordinating frequencies with the RF environment around you is very important.
The best hardware setup is pointless with poor frequency co-ordination.
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Jean-Pierre Coetzee

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Re: Positioning of Omni antenna's
« Reply #2 on: August 24, 2017, 07:11:16 am »

If it's much more than 1 wavelength apart it's probably wasted cable. Put it where there is LOS to the mics and separate it by 1 wavelength and you will be set... 10m may be a bit excessive...

Much more importantly keep cable length as low as possible and make sure you co-ordinate, whichever way you decide to do it, using the manufacturers pre-set frequencies should be fine for 3 mics just make sure those frequencies are clear.
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Word & Life Church

"If you want "loud", then run a piece of sheet metal through a table saw------

If you want "watts"-then plug in a toaster"
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Tom Simenauer

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Re: Positioning of Omni antenna's
« Reply #3 on: August 24, 2017, 07:49:17 am »

Getting all this hardware together is fine but co-ordinating frequencies with the RF environment around you is very important.
By "co-ordinating frequencies" do you mean scanning with the Sennheiser receiver's and getting a good clear channel for each mic?
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Tom Simenauer

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Re: Positioning of Omni antenna's
« Reply #4 on: August 24, 2017, 07:58:21 am »

If it's much more than 1 wavelength apart it's probably wasted cable. Put it where there is LOS to the mics and separate it by 1 wavelength and you will be set... 10m may be a bit excessive...

Much more importantly keep cable length as low as possible and make sure you co-ordinate, whichever way you decide to do it, using the manufacturers pre-set frequencies should be fine for 3 mics just make sure those frequencies are clear.
I just googled 606.5mhz wave length, just under 50cm.
So is that the ideal length to separate the antenna's? To get 100%  LOS i have to have them at the front of the stage either side.
What do most conference Q&A people do with mics in the audience?
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Jean-Pierre Coetzee

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Re: Positioning of Omni antenna's
« Reply #5 on: August 24, 2017, 08:10:09 am »

Go to the sticky section of the wireless forum and read a few of those articles.

Yes honestly 50cm would be enough. 1m would do just fine as well. You will find your 3-5 feet recommendation fits those distances pretty well. You really don't need a ton of space for diversity antennas, the only reason for spacing them further apart would be to increase your coverage range but you would be sacrificing diversity reception.

I have 2 antennae backstage pointed towards the crowd for Q&A in the crowd, but I use directional antennae, with the omni you really won't have a problem.

I would recommend getting them high up and possibly close to the middle of the area they will be used but this would very well be out of your skillset.

Also check your relevant laws in the UK about using wireless mics, from what I remember they are very strict about things there.

For the co-ordination just make sure you use the frequencies from the same bank in the Sennheiser menu and at lease make sure when it is tuned to that frequency there is no dropout when it is used throughout the entire band. I'm not sure if the auto scan keeps wishing the same bank on the units but someone else here will know that and chime in. I generally scan and co-ordinate using WWB...
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Audio Technician
Word & Life Church

"If you want "loud", then run a piece of sheet metal through a table saw------

If you want "watts"-then plug in a toaster"
- Ivan Beaver

Tom Simenauer

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Re: Positioning of Omni antenna's
« Reply #6 on: August 24, 2017, 08:35:20 am »

Go to the sticky section of the wireless forum and read a few of those articles.

Yes honestly 50cm would be enough. 1m would do just fine as well. You will find your 3-5 feet recommendation fits those distances pretty well. You really don't need a ton of space for diversity antennas, the only reason for spacing them further apart would be to increase your coverage range but you would be sacrificing diversity reception.

I have 2 antennae backstage pointed towards the crowd for Q&A in the crowd, but I use directional antennae, with the omni you really won't have a problem.

I would recommend getting them high up and possibly close to the middle of the area they will be used but this would very well be out of your skillset.

Also check your relevant laws in the UK about using wireless mics, from what I remember they are very strict about things there.

For the co-ordination just make sure you use the frequencies from the same bank in the Sennheiser menu and at lease make sure when it is tuned to that frequency there is no dropout when it is used throughout the entire band. I'm not sure if the auto scan keeps wishing the same bank on the units but someone else here will know that and chime in. I generally scan and co-ordinate using WWB...
thanks.
And if i buy 10meter low loss cables so i can have flexibility where i place the antenna's will that be ok?
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Jerome Malsack

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Re: Positioning of Omni antenna's
« Reply #7 on: August 24, 2017, 11:01:23 am »

I like to place them with one out front in the audience and one in the back of the stage.  This config is sometimes hard to reach. But it allows the person to move around and turn around and the antenna will have line of sight.  Hard for the person to turn and move and not have one of the antenna not getting a signal.   The one in the back corner is subject to multi path problems so position could be questioned.  Out from the walls with different distance will help  8 inch from wall and 20 inch from back wall.

circles are antenna  cube is the stage and the rest is open to audience.
« Last Edit: August 24, 2017, 11:06:28 am by Jerome Malsack »
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Jean-Pierre Coetzee

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Re: Positioning of Omni antenna's
« Reply #8 on: August 24, 2017, 12:56:51 pm »

General rule of thumb you want as little excess cable as possible so experiment a bit but make sure you make the cable as short as possible. BNC connectors are not hard to terminate so I would say  cut the excess the moment you can an put another(good quality) connector on the shorter cable.
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Audio Technician
Word & Life Church

"If you want "loud", then run a piece of sheet metal through a table saw------

If you want "watts"-then plug in a toaster"
- Ivan Beaver

Tom Simenauer

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Re: Positioning of Omni antenna's
« Reply #9 on: August 24, 2017, 01:31:19 pm »

General rule of thumb you want as little excess cable as possible so experiment a bit but make sure you make the cable as short as possible. BNC connectors are not hard to terminate so I would say  cut the excess the moment you can an put another(good quality) connector on the shorter cable.
Its not a permanent install, i will pack up after every gig.
AND the system will be used in other halls in London.
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