Does A Splitter Reduce Signal Strength

[Tina Larzelere]

Im using a Wilson Electronics signal amplification system to try to get phone signal in my house. I'm going to attempt using a coaxial splitter like this one to split the amplified signal to multiple indoor antennas for broadcasting to multiple parts of the house, since the house is large and has thick stone walls that block signal very effectively.

What I'm wondering is, once the splitter arrives and I've added it into the system, will I be able to tell immediately if there's a significant signal drop across the splitter, or will it not be apparent until I've bought the second antenna and attached it as well?

To rephrase, if only one port on the splitter is used, is the signal drop to that one port the same as when all four ports are used? Is it the splitter itself which diminishes the signal, or is it the extra devices attached to it drawing part of the voltage away?

You should not be using it that way! This splitter/filter has no in put for power so it is a completely passive device meaning, the power which comes out must be smaller than the power which goes in. Ideally all signal power that feeds into it should get out but that's not going to happen, there will always be some signal loss, no matter what.

If you leave one or more outputs open then the signal will reflect (as it cannot go anywhere, it goes back) and that disturbs the signal on all outputs. This doesn't cause any damage as the signals are very low in power. But you might suffer from ghost images on a TV or general bad reception, so be aware of that! But as a temporary solution until you connect everything properly, it is OK.

As I mention above, the splitter cannot amplify the signal so what power comes in is devided between all outputs. "Drawing voltage away" does not happen and is not the issue. The splitter must be connected properly and only then will it divide the signal equally.

So connecting only one port to a TV and leaving the rest open will actually result in the worst signal at the TV. You get the best signal with no splitter (cable straight into TV). Using the splitter properly (all ports in use) is the middle solution, you would get a decent signal everywhere provided that the signal going into the splitter is strong enough.

My bet is that the splitter you choose is designed for 75 ohms systems like TVs radios and cable modems. My bet is also that your 4G amplifier has a 50 ohms system as that is what is commonly used for cell phones and nearly anything related to it. The fact that the splitter does not mention 50 Ohms or 75 Ohms worries me.

Like using the splitter in the wrong way, the 50 Ohms vs 75 Ohms will not damage anything physically but it will harm the signals such that things are unlikely to work like you want. My bet is that the money you're spending on this will be wasted. You should stick with the products that the 4G extender's manufacturer sells as that is designed to work together. If they don't sell what you need then you're out of luck.

Do realize that what you're trying to do might not work (properly). You have to be sure that the 4G (?) signals you're trying to distribute might not be in the supported frequency range of this splitter. It would be helpful to know which frequency band you are using. I know that 850 MHz is a band used for 4 G but also 1700 MHz up to 1900 MHz is used. And even though the splitter optimistically mentions 2500 MHz, in practice these cheap devices have quite poor performance at such a high frequencies.

Then there's the cables you will be using. Even at 800 MHz a decent cable will attenuate the signal, at 1700 MHz and higher signal losses can be very bad. Use the best quality (lowest loss) cable you can afford.

The splitter does not have a datasheet so it is impossible to know what topology is used inside that specific item. When used properly (with terminators) the attenuation of a typical passive splitter is fixed.

Attenuation would depend on the connected load, however, you should be terminating unused ports with the proper termination resistance. When using the appropriate terminators the attenuation is fixed, nominally -6dB for a typical passive 4-port splitter.

I'd like to record audio coming out of a DJ mixer that has only one output. So I thought I'd use those 'Y' shaped cable splitter plugs which take the L and R cables as input and output to two. Assuming I use decent quality splitters and cables, will this give me broadcast-quality audio?

Not in principle. Assuming the input impedance of both recipients is substantially smaller than the output impedance of the mixer (which it normally is), both do ideally recieve exactly the same signal that each of them would if connected alone.

However in practise, there is one problem which turns up really often if you have audio inputs of different devices in parallel: interference introduced inductively through a ground loop. This is usually either mains hum or artifacts from a switched-mode power supply; both can be pretty nasty. Balanced connections are much less likely to suffer from this, so if the mixer's outputs and both(!) devices' inputs are balanced it should be fine; of course only if you use a fully symmetric splitter. (In the case of TRS connection this means all of the plugs on both Y-cables need to be stereo.)

If any of the devices does not support balanced and you do experience an untolarable amount of static, the canonical solution is a DI-box. I'd recommend the ART DTI.

Unlike an ideal Y-connection, splitting through a DI does change the signal to some degree, but in most more decent of today's models not really notably so.

I have cable and cable internet in my new apartment. The cable comes in to the water-heater closet from the roof and comes out an outlet in the wall of the closet, but there is a 4-way splitter in use before the cable gets to the outlet. It's not used to split the signal at all; the other three output connectors are empty.

Since I added cable internet service (and used a 2-way splitter after the outlet), my tv cable signal is a little fuzzy on some channels; and I was wondering if the cable splitter in the closet is to blame. Could I buy a simple connector to replace the 4-way splitter and see an improvement; or would it be the same, since the splitter isn't actually splitting the signal?

I believe it is splitting the signal, each output will have a specific loss associated. Some splitters will unevenly split the signal (commonly called a tap), which is handy to give a better signal to a longer run or to the cable modem. You can get a straight through connector at any HI store. That said, even these will have some loss of signal, just no where near as much as from a splitter.

If you need a splitter, a powered one (which typically amplifies and cleans the signal by filtering noise) would be a good idea. Otherwise, the straight through mentioned by @BMitch should at least help reduce noise.

A cable splitter WILL result in a degradation of the signal, even if the other ports are unused. One thing you can do is to add terminator caps to each unused port. They are supposed to reduce the degradation.

Note that cheaper cable splitters will actually have a different amount of signal loss for each port. You may see some numbers stamped next to the port itself, something like -2DB, -4DB, etc. This is the signal loss that that specific port will give.

Use a high quality cable wherever you can. Cheap cables are a serious source of signal loss. If you can hold the cable in your hands and see the signal change on your tv, then replace the cable with a good one!!!!!!! I have found that a quad shielded RG6 cable seems to be a good cost effective solution. If you are unable to find one in the correct length, then buy the cable by the foot and attach the cable ends yourself using the proper tools.

A 3.5 db signal loss represents approximately a 50% decrease in signal strength. Usually this isn't a problem, particularly with digital signals (it either gets through or it doesn't) as there is lots of excess signal strength in the feed. But, a second splitter in the chain can degrade the signal another 50%. I'd look at replacing the useless splitter with a straight through connector, which should help.

If I understand correctly, you are using a power divider which is designed to split the incoming signal four ways, and you have three of these with nothing connected. High frequency signals, such as cable TV, depend on uniform signal paths.

One analogy is if you imagine a creek that is split into four smaller creeks. The water ends is split into four parts, each with a quarter of the water, but all of them going the same speed (Though in reality, it'll reduce the speed a bit, so you get just under a quarter of the water-power in each of the small creeks). Now, in your situation, you have three of the creeks blocked. All of the water will end up going down the open creek, but it'll slow down the speed significantly (and make a bunch of nasty waves in the process).

Power dividers do the same thing. They work less well and generate reflections and other problems when their outputs are left open. One solution would be to properly terminate each of the output ports with a 75 ohm impedance which would reduce the interference problems. But, it would be much better to replace it with an adapter (straight through connector) which properly joins the two cables.

unterminated cables cause reflections of the signal back up the wire. The result is very complicated and can affect the clean-ness of the signal at your cable modem. Terminating with 75 ohm terminators help reduce this reflection to zero, but do not prevent the splitting loss from happening (this is because the terminator looks like an infinitely long cable to the rest of the system, the reflections never come back.

Coax splitters are used in video transmissions systems to take a single video feed and branch it off to multiple places. Coaxial cable splitters typically come in 2, 3, 4 and 6 way configurations. Ideally, a coaxial cable splitter maintains the proper impedance environment on both the input and output ports. For video coax systems, this impedance is typically 75 ohms. As the name implies, a coax signal splitter takes the power on the input port and splits it equally among the output ports. For example, a 2-way splitter has one input port and two output ports. It sends half the power of the input signal to one of the output ports. The other half is sent to the other output port.

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