now we use decibels in in all sorts of things so if you're into science you're you're or
you're doing an exam or or whatever else and you like the idea of understanding what decibels is
we're going to do this in about five minutes and strap in the easy way to understand decibels
so decibels got an interesting history so bell laboratories i mean this is going back 100 years
when they first had telephones bell had something called a standard cable mile or a mile of standard
cable scm i think it was scm standard cable mile and it was generally accepted you had a loss on a
telephone and when the customer noticed enough of a loss that was one bell one bell of loss
effectively what they discovered it was not enough granule granule granular
granularity um i sounded like mike then didn't i mess m0 msn sorry mike there wasn't enough
granularity so they made they cut it into tents desi bell okay so when we write
uh decibel it's a small d for the the 10 the debt tenth and then a big b for bell bell laboratories
decibel okay now we use we use the term db in a lot of things optical glass will have dbs radar
reflectivity uses the term dbs in radio we'll use dbs hi-fi systems public address systems dual db's
but we use dbs to reference to understand how loud or more powerful or how clear the glass is
we we use that let's just do a quick table to understand what we mean by db so if something is
0 db and we increase we double the volume all right we have increased it by 3 db
and if we double it again we've increased it by 6 db so every time we double something or three db
let's do it backwards so every time we add 3d bb we're doubling 3d bb every time we add 3 db we're
doubling something but if we've got something that is currently at 13 db and the something else is
16 db well that's actually twice as powerful or clear or reflective or whatever else now
very often when it comes to db we will use it to reference against something known so for instance
in radio circles we might have something called an isotropic radiator which is infinitesimally
small infinitesimally small dot which doesn't exist in real life it's just a bit of fun
it exists as a theoretical point and we can and that point will distribute rf the radio signals
like a sphere like a globe all right but we use that to reference it's an imaginary
piece of data to reference say a dipole which is let's say a wire where most of the rf
will be radiated perpendicular to the wire so we will use the term dbi
maybe when we are taking trying to reference one antenna against another so we've got a dipole
now a dipole in free space at the maximum on its outside of the donut of the dipole
we'll have a gain over an isotropic dipole dbi of around 2 db so we very often shorten that to say
this antenna has a gain of 2 dbi that's what it means all right however there's other ways we can
use this db so we could have let's say so i better color an interesting color oh there's a purple
we could have um what's what's his power isn't it so we could have another system where we have
uh d it's not working very well go blue of d b w is a capital w because mr what okay dbw
and that that's reference to one what so if we have something of that is one d b w
means nothing so far until we find out that we've got this thing this device which is producing
four times the amount of power uh which will be 6 dbw the suffix that we use at the end of these is
determining what we're trying to reference it to the easy way out of this is to say that if
something's at 0 db 3 6 9 10 13 16. what the hell am i doing so that is double three so
that's times two that's times two again that's times two again that happens to be times 10.
so the quick way if you're trying to work out how much power if somebody says you are allowed 13 dbw
you go 13 dd oh that's here so that's times 10 plus there's another 2 because 10 30 minus 10
is 3. 13 is going to be is another 2 again so if you've got this calculation to make in your
head you'll go all right so 10 db is times 10 13 db is another two again so two tens are 20
so it's 20 times the power i confused you now hopefully not that is a quick skim round what
the hell decibels are all right so stick around if you want any more of this science in the meantime
enjoy your enjoy your science enjoy your world and i'll see you next time bye for now
some different colors lovely don't use green on a white board with people by
the way because it doesn't show up very well blue red and black will be fine