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Author Topic: Positioning of Omni antenna's  (Read 1997 times)

Tom Simenauer

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Re: Positioning of Omni antenna's
« Reply #10 on: August 24, 2017, 01:39:14 pm »

The cables i have been recommended are RG213, expensive, but probably worth it.

YET ANOTHER thing to consider i have been told, (wow this antenna stuff is WAY more complicated than audio!!) is its best NOT to have different cable lengths for the antenna's?
But i have a cunning plan if this is so. Nothing better than a hunch.
Use RG213 for the 20 meter cable and a lower grade cable for there 10 meter, so it might even out any important difference?

I am sorry for filling this forum up with newbie questions, but i like to be really on top of things, especially as i am about to do the sound for a very high profile guest, and i want a painless gig.

Thanks for all the help guys
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Jean-Pierre Coetzee

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Re: Positioning of Omni antenna's
« Reply #11 on: August 24, 2017, 01:50:15 pm »

Its not a permanent install, i will pack up after every gig.
AND the system will be used in other halls in London.

In that case sure go for it, would maybe look at getting something that you can use to scan RF with though, if your event is at all high profile a wireless dropping out is a big issue. Likewise maybe some directional antennae are not the worst idea, I can imagine London is quite active and some null points on your antennae might actually be useful.

I've also never had issues with big bags of water(humans) blocking RF with a handheld mic and since most belt packs tend to be placed behind people I find the rear positioning to be better but YMMV. Did have dropout on one mic that followed whatever frequency I selected, I happened to be rewiring the rack and reseating the BNC connectors solved it immediately... Should generally be step 1 for troubleshooting the more I work in this industry the more the problem is quite stupid, like a connector being partially disconnected or just not connecting correctly due to corrosion/oxidation.

Maybe the issue is that your guys have the mics down by their stomaches the whole time and not near their head where it should be.

Also I would strongly recommend power conditioning/UPS for the wireless mics, power issues cause massive headaches with wireless.

Regarding different cable lengths I would likely hope that Henry can pop by and give is some actual science on that.
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Mac Kerr

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Re: Positioning of Omni antenna's
« Reply #12 on: August 24, 2017, 01:53:13 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.

Not necessarily. RF follows inverse square law through the air, it has a defined loss through cable. Getting the antennas closer to the transmitters by running longer cable often has less loss than antennas on shorter cable that are farther from the transmitters. Longer cables may also allow you to position antennas on both sides of the stage to have better coverage of the area of concern.

Mac
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Jean-Pierre Coetzee

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Re: Positioning of Omni antenna's
« Reply #13 on: August 24, 2017, 01:55:13 pm »

Not necessarily. RF follows inverse square law through the air, it has a defined loss through cable. Getting the antennas closer to the transmitters by running longer cable often has less loss than antennas on shorter cable that are farther from the transmitters. Longer cables may also allow you to position antennas on both sides of the stage to have better coverage of the area of concern.

Mac

Why I said as short as possible, what I meant was don't have a 5m coil laying next to the antennae for no reason.
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"If you want "loud", then run a piece of sheet metal through a table saw------

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