video splitter losses

[cordcutter]

I have tried searching this forum but am not able to get to the right post. I am trying to get an answer to the use of a splitter for over the air TV reception. Although the over the air is probably irrelevant. Does having a connected TV of or on effect the signal strength at the other ports? I have assumed it made no difference if the equiptment is on or not, once you split the signal the signals split will always be the same. I have an over the air antennae for broadcast TV. It goes to an amplifier then to a 3 way splitter, One leg to the main TV, two legs to remote TVs with an additional splitter so that I have a total of 4 TVs connected. Believe it or not it worked well until recently when one channel (8) was losing signal down to 0 at times. I noticed when I turned off or disconnected the main TV, a Samsung 60" about 7 months old, the other tvs received an adequate signal at that frequency (ch.8). I replaced connections or switched them with the same results. I called Samsung tech and they suggested I was splitting the signal too many ways. But it was working ok previously and turning off one or two of the remote tvs did not change signal at the main or other remote tv. I am waiting on a call back from them. I just received a call back from my ch. 8 and was reassured their signal has not changed. I do not know if the tuner in the tv could cause this problem but I do not see any other problem. This sure got wordy, sorry. Just trying to supply as much info as possible. I am confused but sometimes the tech staff is more so. Thanks if anyone has read through all this and can help.
Jerry

[pandy]

Many answers but t0 simplify.

First 3 port (way) splitter usually is made as 2 , 2 way splitters combined, so at one of outputs you have signal with power two times higher than ot other two outputs, usually split by 2 give -3.5dB loss on each output, add another split by 2 and add next -3.5dB i.e. 3 outputs -3.5, -7, -7dB. Check your current cable topology, select correct ports (signal to remote splitter should be connected to -3.5dB port).

Next thing is so called return loss of receiver http://en.wikipedia.org/wiki/Return_loss - each receiver should have decent return loss (usually not worse than 10 - 12dB http://www.anritsu.com/en-US/Products-Solutions/Solution/understanding-cable-and-anten...-analysis.aspx - higher - better, 20dB is more than OK) - this can be one of problems - when TV is in standby Return Loss can be very high.

Last thing from most important - isolation between ports/outputs of splitter - also should be highest possible - typical minimum is approx 20 dB - higher better.

How to solve your problem - buy amplifier (low gain - few dB, for sure less than 10dB, low noise - not more than 2 - 3dB) and connect it between TV input and splitter output - this should provide directional coupling i.e. signal will flow in one direction only - from amplifier input to amplifier input (unless amplifier is bilateral but this is not the case for typical in home amplifier without return path).
You can consider placing amplifier before first splitter - this should elevate overall signal level thus make space even for problematic return loss device.

[Cornucopia]

For many of those passive (and a few active) devices, you get better signal (in you used portion) by putting terminating resistors on the unused ends.

@pandy, I think the OP DID mention already having the amp before the split.

Amplifier before the split could be good or bad depending upon many factors. But think about it like an audio signal - even though it operates on a whole different frequency spectrum - you have a gain structure that allows for maximum dynamic range. You don't want to adjust the gain structure of a component beyond the boundaries of the dynamic range of the system; otherwise, you are lowering the signal quality.
An amp might boost the level of peaks into distortion, particularly if it doesn't have adjustable input & output levels.

Another thing to consider might be using a switch instead of a splitter. Do you use multiple TVs at the same time? If not, a switch would give you a single dedicated line to only that device and not incur any loss (well, maybe a very small amount due to the switch).

Scott

[pandy]

For many of those passive (and a few active) devices, you get better signal (in you used portion) by putting terminating resistors on the unused ends.

This can be the source of problem - one of devices can use active termination so when it stays ON then there is no problem due correct port termination, when its going off then it is problem.

@pandy, I think the OP DID mention already having the amp before the split.

Yes, indeed - sorry then but then question about signal level and signal quality (two different things) will popup immediately - my idea to put amplifier was only to compensate losses related to splitter use (signal splitting reduce signal level/power) as i pointed splitting to 2 reduce by 3.5db (at least - this is near perfect case, real life loss is closer to 4dB), splitting to 4 at least 7dB (real life 8dB more likely) add to this loss on connectors, cable etc - that's way reasonable amplifier with moderate 10dB gain should improve slightly situation.

Amplifier before the split could be good or bad depending upon many factors. But think about it like an audio signal - even though it operates on a whole different frequency spectrum - you have a gain structure that allows for maximum dynamic range. You don't want to adjust the gain structure of a component beyond the boundaries of the dynamic range of the system; otherwise, you are lowering the signal quality.
An amp might boost the level of peaks into distortion, particularly if it doesn't have adjustable input & output levels.

Another thing to consider might be using a switch instead of a splitter. Do you use multiple TVs at the same time? If not, a switch would give you a single dedicated line to only that device and not incur any loss (well, maybe a very small amount due to the switch).

Yes, amplifiers are not magic devices that only raise signal level - they also affecting signal - sometimes in a way that make signal very bad and not usable at all.
Termination (passive) can help, isolation (by separating Samsung TV by low gain, low noise amplifier - few dB gain is more than enough), directional couplers are for this frequencies insanely big, expensive and not wideband thus can't be used, other circuits known from RF electronic are simply to expensive.

Side to this i would check cables, connectors - frequently they deteriorate with time and hey can give sometimes very surprising effects.