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Author Topic: RF Switch  (Read 1168 times)

Keith Broughton

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Re: RF Switch
« Reply #10 on: February 06, 2020, 04:33:57 pm »

"Cliff Notes" south of the border.

You're correct: Describes the internal state of the non-selected port. Absorptive means the non-selected port is terminated internally (and not reflecting any energy that might be coming into that port from a connected device such as an antenna or amplifier). Reflective means the non-selected port is unterminated internally and thus will reflect most of any energy that would be coming in from a connected device.
Thanks Henry.
I suspect the non reflective is a better choice as it provides termination if the source is active.
What would be an application for reflective?
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Jason Glass

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Re: RF Switch
« Reply #11 on: February 06, 2020, 05:12:05 pm »

Thanks Henry.
I suspect the non reflective is a better choice as it provides termination if the source is active.
What would be an application for reflective?

Not to interject on Henry's forthcoming reply, but the (usually less expensive) reflective option could be suitable if your connected upstream active device has enough output isolation to reject the reflected energy and still function within desired performance tolerances.  When active devices have an isolator inserted last, immediately before their output ports, they're generally good enough at tolerating reflections and more importantly at not generating IMD products summed from RF energy entering through their output port to power levels that can cause harmful results.  EDIT: Oh, and most importantly not self-destructing due to dispersing excessive energy as heat!

Or, if you're switching a single active device between multiple passive devices (usually antennas), it makes no difference what load the passive devices see when they're switched out of the system.  As long as the out-of-circuit paths are sufficiently isolated from the connected transmission line.

It's a good rule of thumb to use absorptive switches with suitable power handling specs for every application unless a tight budget demands further compromise and commensurate engineering to accommodate reflective components.  Or if the design relies on reflections as part of its desired function (usually to use constructive or destructive interference to intentionally achieve a goal), which is WAY outside of most entertainment pro audio RF system design parameters!
« Last Edit: February 06, 2020, 05:35:52 pm by Jason Glass »
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Russell Ault

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Re: RF Switch
« Reply #12 on: February 06, 2020, 10:30:58 pm »

[...] (usually to use constructive or destructive interference to intentionally achieve a goal), which is WAY outside of most entertainment pro audio RF system design parameters!

We do that all the time with subwoofers, why not with RF as well? :D

-Russ
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Andrew Herbein

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Re: RF Switch
« Reply #13 on: February 07, 2020, 11:25:23 am »

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Henry Cohen

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Re: RF Switch
« Reply #14 on: February 08, 2020, 04:50:06 pm »

Not to interject on Henry's forthcoming reply . .

Feel free to interject anytime; saves me from typing  ;D
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Henry Cohen

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Re: RF Switch
« Reply #14 on: February 08, 2020, 04:50:06 pm »


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