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Author Topic: Wireless transmission trough walls  (Read 16054 times)

kristianjohnsen

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Re: Wireless transmission trough walls
« Reply #40 on: October 30, 2013, 03:28:28 am »

Had to use the snark filter to read this thread.

I'm glad you figured out that point of using 1/2-wave antennas for remote mounting. 1/4-wave only works when there's a ground plane -- typically the case of the receiver. If you hadn't said it I would've.

Yeah, I couldn't get the snarkfest-reasoning, either.

Regarding the 1/2- vs 1/4-wave:  Is this true for IEM transmitters as well?
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David Allred

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Re: Wireless transmission trough walls
« Reply #41 on: October 30, 2013, 08:46:49 am »


Updated:
I took my SLX unit and duplicated the placement and usage area.  One block wall at all times and 2 block walls at other times.  Exterior building walls max at about 135' and I went to extremes in all directions.  Orientation of the receiver and placement within the closet made no difference.  Standing 130' away in the electrical room with 3 step-down transformers (480 - 240-120) between me and the receiver cause no problem.
The one issue that could play a role (I have contacted Shure tech support, but not heard back)... the SLX transmitter is 30mw, while the BLX is 10mw.

Does anyone want to make a prediction on the answer (if the lower output power is a problem)?

David
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Bob Leonard

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Re: Wireless transmission trough walls
« Reply #42 on: October 30, 2013, 09:05:25 am »

All antenna's require a reference to ground in order to perform properly. The wave length of the antenna will determine antenna efficiency and gain, plus even more important to proper operation impedance and resonance.

The best ground will be equal to the antenna resonance (1/4, 1/2, full wave length). The antenna will also perform differently if the ground plane shows as vertical or horizontally aligned with the transmitting element.

I have always felt that a simple understanding of antenna theory (dipole) would help most people understand many of the basic questions asked about proper operation.

Using a dipole, an antenna anyone can build using two (2) pieces of wire and a cable any antenna questions regarding performance can be answered. Note that a horizontal dipole will perform as a directional element with the largest lobes off of the end, and that a vertical dipole will perform as an Omni directional antenna, but with lower gain characteristics. Take time to read at the link below for self satisfaction.
 
http://www.antenna-theory.com/antennas/dipole.php


Bob L. - N1BRH
« Last Edit: October 30, 2013, 09:09:58 am by Bob Leonard »
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Bob Leonard

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Re: Wireless transmission trough walls
« Reply #43 on: October 30, 2013, 09:07:02 am »

Updated:
I took my SLX unit and duplicated the placement and usage area.  One block wall at all times and 2 block walls at other times.  Exterior building walls max at about 135' and I went to extremes in all directions.  Orientation of the receiver and placement within the closet made no difference.  Standing 130' away in the electrical room with 3 step-down transformers (480 - 240-120) between me and the receiver cause no problem.
The one issue that could play a role (I have contacted Shure tech support, but not heard back)... the SLX transmitter is 30mw, while the BLX is 10mw.

Does anyone want to make a prediction on the answer (if the lower output power is a problem)?

David

I have contacted people in Europe using a 10mw transmitter. The antenna is more important than the power put to it.
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BOSTON STRONG........
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Jason Glass

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Re: Wireless transmission trough walls
« Reply #44 on: October 30, 2013, 09:33:00 am »


I have contacted people in Europe using a 10mw transmitter. The antenna is more important than the power put to it.

10mw Boston to Europe?  Wow!  CW QRP?  Please share details of your rig and methods for that!

Bob Leonard

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Re: Wireless transmission trough walls
« Reply #45 on: October 30, 2013, 10:49:11 am »

10mw Boston to Europe?  Wow!  CW QRP?  Please share details of your rig and methods for that!

That was 25 years ago Jason. 10 meter band, Cushcraft A4 at 75', the rig was a Heathkit or homebrew I think, and yes, CW QRP. I have not been active in about 15 years since a snow storm took down both of my towers.
 
The antenna was of course the reason for the contacts. The A4 has a forward gain of 8db minimum.
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Edgar Hernandez

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Re: Wireless transmission trough walls
« Reply #46 on: October 30, 2013, 11:42:08 am »

Looking at a Shure BLX24 or 24R system for an install.  It specs as 300' line of sight.  I want to rack it in the audio closet.  I only need to transmit 100' (absolute max), but there will be a block wall between (7' from the receiver if it makes a difference).   Any hope?

Thanks

Its getting to complicated, are you able to run a mic cable from your mixer to the transmitter that at this point its in the same room as the client properly attach to the top of the 7wall, that way your transmitter is in front of the wireless mic (client) and a professional mic cable will do the job of an extension to the mixer, I find it very simple, but of course, that is if you can or are willing/can to do it, because remember that it will need a power source for the transmitter.
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Jonathan Johnson

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Re: Wireless transmission trough walls
« Reply #47 on: October 31, 2013, 01:24:13 am »

Don't underestimate the attenuation properties of the human body. Once you fill that room full of people, if those people are line-of-sight between the transmitter and the receiver, your RF signal may drop too low to be useful.

Is it an option to remote mount the receiver near the stage, connecting it to the mixer via balanced cable? If you don't need to babysit the receiver, that might be a better option and certainly cheaper if you already have a snake with available channels.

In one of the churches I serve we have an A/T unit (don't remember the model). With 1/4-wave antennas mounted on the receiver at desk level, with the audience between the transmitter and receiver, we were getting a lot of dropouts. Remote mounting 1/2-wave antennas resolved the issue. (Mounting 1/2-wave instead of 1/4-wave on the receiver might have resolved it, too, but we didn't try that.)

Note that the length of the antennas is going to be dependent on the frequency band your receiver is capable of using. They are not all interchangeable.
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David Allred

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Re: Wireless transmission trough walls
« Reply #48 on: October 31, 2013, 02:33:36 pm »

Don't underestimate the attenuation properties of the human body. Once you fill that room full of people, if those people are line-of-sight between the transmitter and the receiver, your RF signal may drop too low to be useful.

Is it an option to remote mount the receiver near the stage, connecting it to the mixer via balanced cable? If you don't need to babysit the receiver, that might be a better option and certainly cheaper if you already have a snake with available channels.

In one of the churches I serve we have an A/T unit (don't remember the model). With 1/4-wave antennas mounted on the receiver at desk level, with the audience between the transmitter and receiver, we were getting a lot of dropouts. Remote mounting 1/2-wave antennas resolved the issue. (Mounting 1/2-wave instead of 1/4-wave on the receiver might have resolved it, too, but we didn't try that.)

Note that the length of the antennas is going to be dependent on the frequency band your receiver is capable of using. They are not all interchangeable.

This a 100' x 100' room.  Estimated max occupancy is 120-ish and dispersed pretty evenly, so a mass of bodies between the mic and receiver is extremely unlikely.
Are you saying that, if the reception is sub par, I should try just the 1/2 waves alone and only buy the wire and brackets if needed?  That would save about $150.
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Bob Leonard

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Re: Wireless transmission trough walls
« Reply #49 on: October 31, 2013, 03:21:39 pm »

Why don't you test the install first, and then get back with any issues you may have. Put the antenna's up high above peoples heads and the body count won't mean much if anything at all.
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ProSoundWeb Community

Re: Wireless transmission trough walls
« Reply #49 on: October 31, 2013, 03:21:39 pm »


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