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Author Topic: Terrific tips for good antenna placement  (Read 6664 times)

Ike Zimbel

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Re: Manfrotto Magic Arm
« Reply #10 on: August 14, 2016, 07:01:49 pm »

In case anyone is not familiar with the term "magic arm" it is a multi jointed positioning system with a hinge swivel and 2 ball swivels that all lock with the tightening of a single knob. They are usually used for mounting camera, but they are real handy for positioning antennas with a clamp on one end and an antenna mount on the other.

There is also a popular variant made by Noga used to hold indicators in machining.

Magic Arm

Noga arm
Yes, these truly are a magical device. One thing to keep in mind when ordering and spec'ing them, though, is to make sure they have 5/8" mic stand adapters on them so you can actually attach your antennas to them.
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~Ike Zimbel~
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Ike Zimbel

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Re: Terrific tips for good antenna placement
« Reply #11 on: August 14, 2016, 07:11:50 pm »

Think of your antennas like lighting fixtures.  You have to put them in the right place.  On the floor behind the roadcase mountain wouldn't be great for a light, and wouldn't be great for an antenna either.
Agreed. One of my preferred spots for RX antennas on arena shows is clamped to the railing inside the vom that is often about 1/3 of the way between the stage and FOH. That usually gives a very clear, unobstructed line-of-site to the stage without obstructing sight lines. I'm not adverse to some longer cable runs to get antennas out where they have a clear shot at the stage. I figure you can make up for line loss in the cable but you can't make up for losses between the Tx and the antenna.
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~Ike Zimbel~
Wireless frequency coordination specialist.
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Radio Active Designs
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Mac Kerr

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Re: Manfrotto Magic Arm
« Reply #12 on: August 14, 2016, 07:12:34 pm »

Yes, these truly are a magical device. One thing to keep in mind when ordering and spec'ing them, though, is to make sure they have 5/8" mic stand adapters on them so you can actually attach your antennas to them.

Or Matthews studs if that is what you use.

Mac
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Mac Kerr

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Re: Terrific tips for good antenna placement
« Reply #13 on: August 14, 2016, 07:15:25 pm »

Agreed. One of my preferred spots for RX antennas on arena shows is clamped to the railing inside the vom that is often about 1/3 of the way between the stage and FOH. That usually gives a very clear, unobstructed line-of-site to the stage without obstructing sight lines. I'm not adverse to some longer cable runs to get antennas out where they have a clear shot at the stage. I figure you can make up for line loss in the cable but you can't make up for losses between the Tx and the antenna.

Of course there's also this low loss antenna cable system for those really long runs. I have used them a few times and I am a big fan. A little pricy though.

Mac
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Keith Broughton

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Re: Terrific tips for good antenna placement
« Reply #14 on: August 14, 2016, 08:21:29 pm »

Hi Keith,

Here you go:


Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.
Thanks :)
Much lager spacing than I first thought. TX at one end and RX at the other.
Nice!
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Jason Glass

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Re: Terrific tips for good antenna placement
« Reply #15 on: August 14, 2016, 08:38:44 pm »

Of course there's also this low loss antenna cable system for those really long runs. I have used them a few times and I am a big fan. A little pricy though.

Mac
Hear, hear. I own two pairs and consider them well worth their price. Nothing more cost & RF loss effective on the market for covering distant RX zones for RFPL and/or mics.

BTW and FWIW, Spectrum Sound in Nashville has a lightly used pair of the older version (SMA RF connectors & FC-APC fiber connectors) for sale. I think they also have 50m of compatible duplex tactical fiber on a reel available.

Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.

Scott Holtzman

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Re: Terrific tips for good antenna placement
« Reply #16 on: August 14, 2016, 11:57:56 pm »

Of course there's also this low loss antenna cable system for those really long runs. I have used them a few times and I am a big fan. A little pricy though.

Mac

Mac - That is slick, a two way block downconverter.  I bet that is basically the same thing we use to distribute cable TV over fiber (which has a return path).  I know I am out of my element but what does something like that list for?  Would be interesting to try the CATV unit.

One other question to satisfy my never ending curiosity.  In the land mobile and cellular world putting a tower mounted preamp (with filtration) between the antenna and feedline with just enough gain to make up the cable run is standard practice.  DB Products and CellWave/Phelps were popular brands.  They had low noisefloors and were great tools as we got pushed up into the 800Mhz spectrum.  You could reuse the old 7/8 LDF feedline with the higher frequency and not take the hit on the feedline loss.

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Henry Cohen

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Re: Terrific tips for good antenna placement
« Reply #17 on: August 15, 2016, 09:48:54 pm »

Mac - That is slick, a two way block downconverter.

Not BDC's: they are RF over fiber media converters. RF in - light out / light in - RF out.

Quote
One other question to satisfy my never ending curiosity.  In the land mobile and cellular world putting a tower mounted preamp (with filtration) between the antenna and feedline with just enough gain to make up the cable run is standard practice.  DB Products and CellWave/Phelps were popular brands.  They had low noisefloors and were great tools as we got pushed up into the 800Mhz spectrum.  You could reuse the old 7/8 LDF feedline with the higher frequency and not take the hit on the feedline loss.

The amplifier with a measure of filtering making up solely for coaxial losses is pretty much the idea behind the better designed active LPDA's from Sennheiser, Shure and Wisycom. But with proper coax, and RF system gain structure, preamps are unnecessary. As for the 7/8" feedline: Forgetting for the moment even the cheapest variant is about $2.50/ft and connectors are $40ish each, that coax is not design for more than one deployment - the shield will kink, distort or break after just a two or three wraps. And never mind the physical space a couple hundred foot coil would take up. I've used 7/8" flexible on a couple of shows but was essentially bought by the production and discarded afterwards or permanently installed for use each year by the returning event.
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Henry Cohen

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Mac Kerr

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Re: Terrific tips for good antenna placement
« Reply #18 on: August 15, 2016, 10:22:06 pm »

I've used 7/8" flexible on a couple of shows but was essentially bought by the production and discarded afterwards or permanently installed for use each year by the returning event.

And then there was that Heliax on the roof of the south tower of the WTC. I think the coil was 6' in diameter.

Mac
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Henry Cohen

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Re: Terrific tips for good antenna placement
« Reply #19 on: August 16, 2016, 02:12:28 pm »

And then there was that Heliax on the roof of the south tower of the WTC. I think the coil was 6' in diameter.

Forgot about that time: That was 18 years ago. The coil was bigger than Hallie :)
« Last Edit: August 16, 2016, 03:18:48 pm by Mac Kerr »
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Henry Cohen

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ProSoundWeb Community

Re: Terrific tips for good antenna placement
« Reply #19 on: August 16, 2016, 02:12:28 pm »


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