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Author Topic: Terminating outputs on antenna splitter  (Read 386 times)

Keith Broughton

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Terminating outputs on antenna splitter
« on: September 01, 2014, 03:41:55 pm »

I am using a Sennheiser ASA1 4 way antenna splitter on only 2 receivers.
Should I put termination plugs on the unused outputs of the splitter?
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Jano Svitok

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Re: Terminating outputs on antenna splitter
« Reply #1 on: September 02, 2014, 03:01:11 am »

I suppose you don't have to. ASA 1 manual doesn't mention terminators at all, and we use it also without any plugs (2x omni antennas + 2x boosters + ASA1 + 2x receivers powered from ASA).
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Scott Holtzman

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Re: Terminating outputs on antenna splitter
« Reply #2 on: September 02, 2014, 03:50:00 am »

I suppose you don't have to. ASA 1 manual doesn't mention terminators at all, and we use it also without any plugs (2x omni antennas + 2x boosters + ASA1 + 2x receivers powered from ASA).

To me it's an informed decision type of thing.  The reason for terminators is to keep the unconnected port(s) from acting like an antenna.  If sufficient signal is present it could come back into the preamp and hetrodyne (mix) with the wanted signals and produce sufficient harmonics to raise the noise floor or wipe the front end out on the RX's entirely so nothing would be received. 

If you use in multiple locations I would highly recommend. 

A terminator is simply a resistor that places a load on that port to shunt and received signals to ground.

If you happen to have an RF spectrum analyzer take a look at the noise floor without and without the terminators.  I bet it moves at least 6dbm

Of course you should not be using a wireless path with only a 6db fade margin but that is a discussion for another day.

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Scott AKA Skyking
Passion Fuel Productions, Cleveland OH

Keith Broughton

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Re: Terminating outputs on antenna splitter
« Reply #3 on: September 02, 2014, 08:18:57 am »


If you use in multiple locations I would highly recommend. 


Good point!
Terminators it is.
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Jens Palm Bacher

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Re: Terminating outputs on antenna splitter
« Reply #4 on: September 02, 2014, 08:40:34 am »

I am using a Sennheiser ASA1 4 way antenna splitter on only 2 receivers.
Should I put termination plugs on the unused outputs of the splitter?
Remmeber the ASA 1 puts DC on the outputs for powering G3 receivers via the coax. So a simple ternminator sounds like a bad idea.
Of course there will be some reflection back into the splitter from any unused outputs, but i'm sure you will find that it is not significant if you measure it.
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Scott Holtzman

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Re: Terminating outputs on antenna splitter
« Reply #5 on: September 02, 2014, 09:05:14 am »

Reflection is a transmitter issue not a receiver issue.  The issue is the intermodulation products.  If there is DC you will need to put a capacitor in series with the resistor to block the DC when you construct the terminator.  About 4.7uF with the negative side of the cap towards the DC source.


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Scott AKA Skyking
Passion Fuel Productions, Cleveland OH

Jens Palm Bacher

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Re: Terminating outputs on antenna splitter
« Reply #6 on: September 02, 2014, 11:15:50 am »

Reflection is a transmitter issue not a receiver issue.  The issue is the intermodulation products.  If there is DC you will need to put a capacitor in series with the resistor to block the DC when you construct the terminator.  About 4.7uF with the negative side of the cap towards the DC source.
Asked the local Sennheiser RF specialist. Quote: "if terminators had mattered they would have been included with the gear"
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