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Author Topic: Max length of RG58 cable without booster?  (Read 10053 times)

Keith Broughton

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Re: Max length of RG58 cable without booster?
« Reply #10 on: September 18, 2017, 07:54:03 AM »

It's a balancing act between a specific cable's loss vs. antenna gain - free space loss - polarization mismatch loss - multipath loss. Be mindful of Fresnel zones. High loss cables such as RG58 can be lossier than free space, while modern low loss coax can be far less.

http://www.timesmicrowave.com/calculator/

https://www.pasternack.com/t-calculator-fspl.aspx

http://www.antenna-theory.com/basics/polarization.php

http://www.radio-electronics.com/info/propagation/multipath/multipath-propagation-basics-tutorial.php

https://en.m.wikipedia.org/wiki/Fresnel_zone

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Thanks for the links :)
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Jason Glass

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Re: Max length of RG58 cable without booster?
« Reply #11 on: September 18, 2017, 09:23:18 AM »

Thanks for the links :)

You're welcome!

BTW, it may seem counterintuitive because a lossy cable that isn't faulty will almost always have less total loss over a given distance than free space over the same distance.  Where it gets weird is when you compare different lengths of cable and free space as portions of a given path distance.  I hope these graphics help.

brian maddox

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Re: Max length of RG58 cable without booster?
« Reply #12 on: September 18, 2017, 04:17:23 PM »

It's a balancing act between a specific cable's loss vs. antenna gain - free space loss - polarization mismatch loss - multipath loss. Be mindful of Fresnel zones. High loss cables such as RG58 can be lossier than free space, while modern low loss coax can be far less.

http://www.timesmicrowave.com/calculator/

https://www.pasternack.com/t-calculator-fspl.aspx

http://www.antenna-theory.com/basics/polarization.php

http://www.radio-electronics.com/info/propagation/multipath/multipath-propagation-basics-tutorial.php

https://en.m.wikipedia.org/wiki/Fresnel_zone

Sent from my Nexus 5 using Tapatalk

This with its links could easily be a sticky.  So much great information....
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brian maddox
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Keith Broughton

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Re: Max length of RG58 cable without booster?
« Reply #13 on: September 18, 2017, 06:25:51 PM »

Those loss charts really support the idea of good quality cable with the antenna closer to the transmitter.
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Lyle Williams

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Re: Max length of RG58 cable without booster?
« Reply #14 on: September 19, 2017, 07:56:10 AM »

The reception game is about signal-to-noise, not just raw signal power.
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Jason Glass

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Re: Max length of RG58 cable without booster?
« Reply #15 on: September 19, 2017, 12:37:33 PM »

The reception game is about signal-to-noise, not just raw signal power.
That's correct, but neither can be ignored and optimization of both is the secret to solid performance.

FWIW, in systems where I've done exhaustive path loss calculations to predict that IEM receivers have no less than 1500uV at their furthest expected distance from the TX antenna, none have had dropout issues. Some have had audible noise issues due to nearby emitters such as video floors and LED drivers, but having signal strength to spare is what allows one to use RX RF attenuation to mitigate those types of problems.

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Jason Glass

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Re: Max length of RG58 cable without booster?
« Reply #16 on: September 19, 2017, 12:48:53 PM »

Those loss charts really support the idea of good quality cable with the antenna closer to the transmitter.
I think we agree but I'm a little confused because it depends on whether you refer to an IEM system or a microphone system.

It's safe to say that it's best to cover as much of the distance between TX and RX as you can with modern low loss cable and as little free space between them as possible.

Before someone pipes in about RF overload, IMHO that issue is far less likey to cause real world trouble than insufficient RX signal strength, especially if you place antennas in a way that prevents TX and RX from getting within 10 feet of each other.

edit: OK, so not strictly as close as possible.   More like minimal while maintaining even performance area coverage.

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« Last Edit: September 19, 2017, 12:57:07 PM by Jason Glass »
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Re: Max length of RG58 cable without booster?
« Reply #16 on: September 19, 2017, 12:48:53 PM »


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