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Author Topic: Wireless transmission trough walls  (Read 15989 times)

Steve M Smith

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Re: Wireless transmission trough walls
« Reply #30 on: October 28, 2013, 09:40:00 am »

Teach a man to fish, and you can sell him a ton of accessories.

"Give a man a fish and he will eat for a day.  Teach a man to fish and he will buy an ugly hat".

- Scott Adams, Dilbert creator.


Steve.
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Tim Perry

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Re: Wireless transmission trough walls
« Reply #31 on: October 28, 2013, 05:18:35 pm »

If the pond is in the woods and a tree falls and crushes his skull, will you hear the fish.

That is deep.
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Brian Adams

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Re: Wireless transmission trough walls
« Reply #32 on: October 28, 2013, 10:42:35 pm »

It shouldn't be 75ohm, that's video cable. For audio over RF the industry standard is 50ohm cable and connectors.

For what it's worth, I've used 100' and greater lengths of standard RG6 75 ohm video cable (Belden 1694A) with Shure ULX receivers and UA870 antennas many times with no appreciable loss of RF performance. Also with Lectrosonics IFB transmitters and Shure PA805 antennas. I assume it would work fine with IEM transmitter as well, but I've never tried.

I know it's not "right", but hey, it works.
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Brian Adams
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Mac Kerr

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Re: Wireless transmission trough walls
« Reply #33 on: October 28, 2013, 10:59:00 pm »

For what it's worth, I've used 100' and greater lengths of standard RG6 75 ohm video cable (Belden 1694A) with Shure ULX receivers and UA870 antennas many times with no appreciable loss of RF performance. Also with Lectrosonics IFB transmitters and Shure PA805 antennas. I assume it would work fine with IEM transmitter as well, but I've never tried.

I know it's not "right", but hey, it works.

It won't work as well with IEM transmitters. The receive antenna has an impedance that varies with frequency just like a speaker, so the 50Ω impedance spec is not dead on anyway. Very often RG59 will work fine as antenna cable for wireless mics, it often has less loss than RG58 which is 50Ω. It has more loss however than good antenna cable.

For IEM transmitters the antenna/cable combination is much more important to keep at 50Ω.

Mac
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Brian Adams

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Re: Wireless transmission trough walls
« Reply #34 on: October 28, 2013, 11:03:39 pm »

It won't work as well with IEM transmitters. The receive antenna has an impedance that varies with frequency just like a speaker, so the 50Ω impedance spec is not dead on anyway. Very often RG59 will work fine as antenna cable for wireless mics, it often has less loss than RG58 which is 50Ω. It has more loss however than good antenna cable.

For IEM transmitters the antenna/cable combination is much more important to keep at 50Ω.

Mac

I agree. But like I said, I've used that same 75 ohm RG6 on IFB transmitters with good results. Those are probably higher powered than a typical IEM transmitter though, which I'm sure makes a difference.
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Brian Adams
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kristianjohnsen

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Re: Wireless transmission trough walls
« Reply #35 on: October 29, 2013, 05:08:43 am »

It won't work as well with IEM transmitters. The receive antenna has an impedance that varies with frequency just like a speaker, so the 50Ω impedance spec is not dead on anyway. Very often RG59 will work fine as antenna cable for wireless mics, it often has less loss than RG58 which is 50Ω. It has more loss however than good antenna cable.

For IEM transmitters the antenna/cable combination is much more important to keep at 50Ω.

Mac

I recently heard that the center-pin and center-pin socket of the BNC connectors are slightly different for 50Ω and 75Ω, meaning that a 50Ω patch panel will have a lesser connection after someone has used 75Ω cables on it.

Does anyone know if there is truth to this claim?
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Brian Adams

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Re: Wireless transmission trough walls
« Reply #36 on: October 29, 2013, 11:13:02 am »

I recently heard that the center-pin and center-pin socket of the BNC connectors are slightly different for 50Ω and 75Ω, meaning that a 50Ω patch panel will have a lesser connection after someone has used 75Ω cables on it.

Does anyone know if there is truth to this claim?

That's incorrect, 50 and 75 ohm center pins are the same diameter, and the connectors can mate without damage.
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Brian Adams
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Tim Perry

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Re: Wireless transmission trough walls
« Reply #37 on: October 29, 2013, 08:52:18 pm »

I recently heard that the center-pin and center-pin socket of the BNC connectors are slightly different for 50Ω and 75Ω, meaning that a 50Ω patch panel will have a lesser connection after someone has used 75Ω cables on it.

Does anyone know if there is truth to this claim?

from Wiki:  "The different versions are designed to mate with each other,[2] and a 75 ohm and a 50 ohm BNC connector which both comply with the 1978 standard, IEC 169-8, will mate non-destructively. At least one manufacturer[9] claims very high reliability for the connectors' compatibility.

At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects.[10] BNC connectors were thus originally made only in 50 ohm versions, for use with any impedance of cable. Above this frequency, however, the mismatch becomes progressively more significant and can lead to signal reflections."

...Type N connectors are another story
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Jonathan Johnson

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Re: Wireless transmission trough walls
« Reply #38 on: October 30, 2013, 01:29:58 am »

... It is now in the hands of my client to determine if they want to pay the extra $220 for the 2) 25 ft antenna wires and the 1/2 wavelength antennas to replace the 1/4 wavelengths that are stock on the BLX system...

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.
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Stop confusing the issue with facts and logic!

kristianjohnsen

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Re: Wireless transmission trough walls
« Reply #39 on: October 30, 2013, 03:27:00 am »

from Wiki:  "The different versions are designed to mate with each other,[2] and a 75 ohm and a 50 ohm BNC connector which both comply with the 1978 standard, IEC 169-8, will mate non-destructively. At least one manufacturer[9] claims very high reliability for the connectors' compatibility.

At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects.[10] BNC connectors were thus originally made only in 50 ohm versions, for use with any impedance of cable. Above this frequency, however, the mismatch becomes progressively more significant and can lead to signal reflections."

...Type N connectors are another story


Hi Tim.

Thank you.  Any chance you could pass along a link to the article?  I would like to show it to someone else :).
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ProSoundWeb Community

Re: Wireless transmission trough walls
« Reply #39 on: October 30, 2013, 03:27:00 am »


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