Signal Loss Percentage = 1 minus (1
divided by dB power factor)
% Signal Loss = 1 - (1 / (dB power Factor))
2-way Splitter Signal loss (percentage)
|%Loss = 1 - (1 / 2.28)(2.28
is the dB power factor for 3.5dB)
%Loss = 1 - ( 0.44)
%Loss = .56 or 56%
2-way splitter decreases your signal strength by 56%.
4-way Splitter Signal Loss (percentage)
|%Loss = 1 - (1 / 5.01)
%Loss = 1 - (0.2)
%Loss = .8 or 80%
4-way splitter decreases your signal strength by 80%.
What happens when you split your cable multiple times? This
is how you would add up the two splitters in the example: 3.5dB loss + 7.0 dB loss = 10.5 dB loss
The 10.5dB loss number is not in the table, so
we'll estimate it another way...
We lose 56% of the original signal, then ANOTHER 80% of the remaining signal. 1- (0.56 *
(1 - 0.80)) = 0.888 or 88.8% signal Loss. After these two splitters almost 90% of your
original signal strength is GONE. By the way, if you know the 10.5dB loss number, the
ACTUAL loss for a 10.5dB signal drop is 91%, so we were pretty close. It's no wonder
your TV picture is so crummy, even after going through just ONE splitter, let alone TWO!
When shopping for an amplifier, bigger dB
numbers are not always better. Too much of a good thing can actually make things worse for
you. It is easily possible to make your TV signal WORSE by boosting the signal too much.
This is called OVERDRIVING the signal. It is bad because it causes buzzing, bleeding or
blotchy colors, and white streaks - among other problems. The best strategy is to keep the
signal strength as close as possible to the signal strength provided by your cable
company. In the real world this is done through painstaking calculations of cable lengths
and cable splits throughout the house. However, most people don't know how to compute
gain/loss so they take a SWAG (simple wild-ass guess) at it by throwing an amplifier in
place, in the hope that it does what they want. Believe it or not, this actually works
most of the time! If that were not the case, my feedback from customers would certainly not be so good.
Fortunately a good guess works for about 95% of the simple situations out there.
||dB Power Factor
||Voltage or Current Ratio
Amplification (also known as dB boost):
Amplification is the process of boosting a signal. Amplification is generally needed for
homes with multiple TVs, or where long cable runs (>150 feet) are used. Amplification
is generally a good thing, except for the fact that cheap TV amplifiers don't do a real
good job, and can actually make the TV signal worse. Cheap amplifiers add
"noise" to the signal, which can then be seen as ghosts, buzzing, snow, lines
through the picture, and other annoying things. Good amplifiers do their job so well that
they don't add ANY noticeable noise to the TV signal. Good amplifiers make your picture
look BETTER, and don't cause side effects like ghosts, lines, or snow. The boost is
measured in dB.
Example: Based on our Decibel Table above, a 1-port amplifier provides 15dB
of forward signal gain, which means that the signal is almost 32 times stronger coming out
of the amplifier than the signal going in. In addition, a 1-port amplifier has a
return path loss of 0.5 dB, which means it causes an 11% loss on any signal going back
toward the cable company. Here is a quick summary table:
|# Amplifier Ports
||Forward Signal Boost Factor
||Return Path Signal Loss (dB)
||Return Signal Loss Percentage
|4 (UG model)
|8 (UG model)