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Splitters & attenuators, the difference?

dddd

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#1
How can I tell the difference between a 2 way splitter & an attenuator?

Can I also use 2 2-way splitters to get 3 signals?

Thanks.
 

allcards

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#2
How can I tell the difference between a 2 way splitter & an attenuator?

Can I also use 2 2-way splitters to get 3 signals?

Thanks.
attenuators are used for reducing signal levels so there is a little button that can be rotated to get the correct level needed, and it usally has the word attenuator on the label.

you could us 2 by 2 way splitters, but why not use a three/four way splitter that is designed to do a 3/4 wat split with a lot less signal loss.

regards
 

parky

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#4
You have to be careful with leaving splitters open-ended in those cases - co-axial transmission doesn't like reflections etc, so I would not recommend this. This is akin to old BNC ethernet having to have terminators.
 

GaryM

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#5
I run 1 x Dreambox 500C, 1 x Eurovox Max and 1 x 10Mb internet connection.

Which would be the better splitter to buy considering the above?

3 way, each port 6.2dB out
3 way, 2 ports 3.5dB, 1 port 7dB

Would a higher or lower figure allow greater signal strength to that port?
 

GaryM

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#6
Bump.

Anybody know the answer to my question above? It may well help the OP too as he also wants 3 splits.
 

dddd

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#7
Yeah, I'd like to know that too. Also any links to maplin or some other shop would help too.
Thanks!
 
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#8
dBs ....

Re splitters (and with apologies for length of explanation):

dBs are on a logarithmic scale:
3dB = 1/2 power
6dB = 1/4 power
9dB = 1/8 power etc

A perfect (theoretical) lossless splitter would give -3dB to each leg of a two output splitter. A practical 2 way splitters has losses of about 3.5dB to each output. Clearly a 3 way splitter can't give -3.5dB (about half power) to each of 3 outputs.

Generally, the lower the loss (3.5 rather than 6 or 7 dB), the better.

By design a (symmetrical) 3 way splitter can give equal outputs (eg -6.2dB in your example). ie only 1/4 of power goes to each of 3 ports (and 1/4 power dissipated in the splitter). In the context of a cable box which seems to be fairly sensitive to level, this is a loss that may well require amplification in order to receive all channels. It's difficult to be sure.

The non-symmetrical splitter (3.5/3.5/7 dB) would allow the two cable boxes to receive the maximum signal BUT would result in a significantly lower signal (-7dB) being available for the internet modem. I have no experience with this but it could be worth a try.

With either option of splitters, it is possible/probable that an inline amplifier (usually quoted as about £9 from Argos) may be required. On balance, of the two options you give, I would probably go for the 3.5/3.5/7 dB splitter.

As an alternative, you can buy cable splitter amplifiers for about £10 with up to 3 outputs. These should allow you to set levels such that the cable boxes have optimal Signal level. For example, from a Hongkong seller there is this item (£7.50 inc postage!!!!) and the seller has >98% with 35000 sales.

h**p://cgi.ebay.co.uk/NEW-CATV-Broadband-Drop-Signal-Booster-Amplifier-220V_W0QQitemZ150107196470QQcategoryZ61395QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

For £7.50, I'd be tempted to have a go for one of these rather than buy a splitter and the maybe have to buy an amplifier as well.

Hope that helps.
 

GaryM

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#10
Cheers Gary, really good post.

Would a general 4 port digital TV booster to ok to use, main cable to feed the booster and then 3 outgoing cables?
When a booster mentions z 20dB gain is it as simple as it adds 20dB onto the pre boosted signal? ie pre boost 35dB, connect 20dB gain booster then have 55dB spread accross the booster out ports (ignoring any losses)?
 
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#11
4 Port Amp

Hi guys,

As you suggest, if you have a 4 port device with 1 i/p and 3 o/p, then yes all o/ps would be 20db greater than the i/p (for normal/small signal inputs). The device has 20 db gain PLUS enough gain to compensate for the splitting losses.

Note that the amplifier will (in general) amplify the Signal AND the Noise.

On the downside, it is reported that cable boxes need the signal level to be within a fairly close tolerance....perhaps say 87-96 dB. If you had, say 84dB without the splitter/amp, you would get 104 dB with the spliiter/amp (unless the amp saturated). This could give your cable box as much trouble as too little signal.....You would need to attenuate the signal back down to the acceptable level.

So if you buy a splitter/amp it would be wise to get one that has a gain control:
Typically 0- to 20 dB of gain (variable control)
1 input
2 or 3 outputs (3 if you want to feed 2 cable boxes and internet modem)
Band that covers entire cable band (say up to 1000MHz)
F-Type connectors (if thats what most of your equipment has)

Cheers
 
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#14
Just a quick postscript...

If all you want to do is split a cable feed to supply existing tv cable box plus a Dreambox, all that may be required is a two way splitter (with about 3.5 dB of loss to each split feed).

With this loss, it is quite likely that the system will work just fine without the need for any additional amplification.

Just suck it and see. If you don't get all the channels, suspect low signal level.
 

fisal

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#15
from one feed i use 2 cable box and 2 modems, so i think im losing loads of signal
 
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#16
Acid Test

I suppose the acid test is whether all tv and internet work properly.

Also if all/most of the equipment was connected when cable provider made their installation, they would have set their (street) gain/attenuation settings to compensate accordingly.

And finally, most cable boxes probably have an AGC (automatic Gain Control) to compensate for variations in signal level and do its best to make sure the receiver is hit with a suitable signal level.
 

dddd

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#18
Well, my original post was because I have 2 2-way splitters and I was wondering if they would work, or that the signal level would be too low. I realise that the best solution would be a 3-way splitter or and amplifier as posted above.

Thanks!
 

gentlex

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#19
Well, my original post was because I have 2 2-way splitters and I was wondering if they would work, or that the signal level would be too low. I realise that the best solution would be a 3-way splitter or and amplifier as posted above.

Thanks!
m8 i run a 3way and two 2way on my line and my signal is excellent even with a dreambox old tuner. most household signal is quite capable of carrying 4boxes and 4 modem without much lost to signal quality or strength. but with most things ther is a limit of how much a single line can carry before the quality starts to degrades.
 

asmaniac

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#20
splitter tend be used to split a signal without loss and attenuator will reduce signal strength...best to stay away from attenuators