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Electronics question: Update w/new question

B

blackdogdeek

Lifer


UPDATE: new question: let's say that with a splitter the reception on the hdtv isn't that great. if i put an signal booster or amplifier BEFORE the splitter, will the reception be better at the hdtv?

i know it sounds pretty obvious but the guy at radio shack said that the bad signal is already there and that amplifying it would just mean making the bad signal stronger (which didn't really make sense but i didn't really have any idea so i took his word).

thanks in advance
 
If you had a 4 way splitter each port would likely be about -7 dB. An ideal 4 way splitter would have four -6dB ports.

Edit: Is this a homework question or an actual usage question? -7dB is about what you'll see in an actual implementation.
 
the loss from the splitter will be -4db on each terminal(if that is on the spec on it). FYI, it is parallel.

What you should be more worried about is if the signal can handle the loss for 4 terminals. in most cases it can.
 
Tip: if you're going to amplify the signal, do so before the splitter, not after the splitter.
 

Try thinking about the problem from an energy standpoint. The signal strength is halved (at best) by a cable splitter (-3db). A four-way splitter must halve each half (-6bd).
 
Originally posted by: PowerEngineer

Try thinking about the problem from an energy standpoint. The signal strength is halved (at best) by a cable splitter (-3db). A four-way splitter must halve each half (-6bd).
Click to expand...

Exactly. Plus about 1 dB loss because of reflections, etc. and you get about -7dB at each port.
 
There is no right or wrong answer as different make/model splitters are made differently. Check the specs on whatever you decide to buy.
 
Originally posted by: blackdogdeek
ok so far i think the only replies contradict each other.

how sure are you of your answers?
Click to expand...

You are confused. For each INDIVIDUAL terminal, no, the gain will not change. However, for the combined, the gain will change.
 
Originally posted by: Gibson486
Originally posted by: blackdogdeek
ok so far i think the only replies contradict each other.

how sure are you of your answers?
Click to expand...

You are confused. For each INDIVIDUAL terminal, no, the gain will not change. However, for the combined, the gain will change.
Click to expand...

ok, so in the 4-way splitter A, B, C and D will each lose -4db? (assuming the exact same composition as the 2-way splitter except for the number of splits)
 
Originally posted by: RaynorWolfcastle

Edit: Is this a homework question or an actual usage question? -7dB is about what you'll see in an actual implementation.
Click to expand...

an actual usage question.

i have a 2-way splitter from the main cable line into our bedroom. it originally split the line to the replayTV and the mythTV. the replayTV has a coax out that runs to the antenna in of the HDTV. the mythTV has a vga out that runs to the vga in of the HDTV.

now when i tried to use the tuner on the HDTV to pick up the signals on the line, it had a difficult time reading any of the channels. so i removed the splittler and ran the line directly to the HDTV just to test if it could pick up the channels that way. when i removed the splitter it tuned all the channels perfectly.

so i figured that splitting the line to replay and myth + plus the split inside the replay was too much of a signal degradation and that's why the HDTV couldn't pick up any channels originally.

so what i did was split the line once, 1 terminal as the HDTV and one as the replayTV (the mythTV is not hooked up in this situation). and still the HDTV was able to tune the channels and they look pretty good. this is ok except now i don't have the mythTV hooked up.

so what i wanted to do was get a 4-way splitter, have 1 terminal be the HDTV, 1 be the replayTV and the last be the mythTV. but i am worried that i will lose too much of the signal and the HDTV won't be able to tune the channels (and the replayTV and mythTV will also have poor signal).

i was hoping that if the 4-way splitter only loses the same amount per terminal as the 2-way that i would be ok.
 
OK, what you have to realize is that the -4dB tells you the output signal power relative to the input signal power, not the losses. A 4dB loss is huge, it would mean that over half your signal power is lost. Now, remember that an ideal 50:50 splitter with no losses will give you -3dB at each output port (by conservation of energy). So with a real-world 50:50 splitter you'll get something like -4dB at each output port.

With that said, you wouldn't likely gain much by using a 4-way splitter. Essentially, you're already very near your HDTV tuner's sensitivity and gaining a dB or two would not be likely to solve your problem. In the best case, you could perhaps use an asymmetric splitter maybe a 3 way splitter that's 50:25:25 (this would have ports that are -4dB, -7dB and -7dB or so) and plug the TV on the -4 dB port.

More than likely however, you'll need to amplify your signal or have your cable company increase the amount of power they supply. In any event, you should amplify the signal BEFORE you do any splitting.
 
I bought an amplified splitter a few months ago and it made a big difference. Yes, fuzziness will be amplified somewhat, but if you are getting blockiness and cutouts due to weak signal, it'll fix your problem. I used to have severe blocking/audio problems and completely blank channels before I bought it - now it's all good.
 
It all depends on where you put the amplifier.

You want to do it BEFORE the splitter and BEFORE any long cable run.

If instead you output the amplifier directly to your TV after it has been split and after a long cable run, you will not notice much, if any, improvement at all.
 
Originally posted by: joshsquall
I bought an amplified splitter a few months ago and it made a big difference. Yes, fuzziness will be amplified somewhat, but if you are getting blockiness and cutouts due to weak signal, it'll fix your problem. I used to have severe blocking/audio problems and completely blank channels before I bought it - now it's all good.
Click to expand...

do you mind if i ask how much you paid and where you got it?
 
Let me add this: I have a rather large antenna on my home with a built-in amp.

Without the amp, I can pickup only a handful of stations.

With the amp powered, I can pick them all up.

If the only problem with your signal is poor reception due to a splitter, replace it with a quality splitter, and a decent signal amplifier and you should have no problems.
 
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