TV signal strength
- Thread starter Softus
- Start date
DB alone is meaningless, you need to know what the reference point is for it to make any sense.
Also note that an amplifier may well make things worse if it is noiser than the input stage on the receiver. Generally I would advise against use of amplifiers on a weak signal. Sure use them to distribute an acceptable signal to more receivers but they are no substitute for a decent sufficiantly high gain antenna properly mounted.
Also note that an amplifier may well make things worse if it is noiser than the input stage on the receiver. Generally I would advise against use of amplifiers on a weak signal. Sure use them to distribute an acceptable signal to more receivers but they are no substitute for a decent sufficiantly high gain antenna properly mounted.
on a tangent...
TV reception here is rather poor due to hills so I have been using cable. However I recently bought a simple digital box, and get good reception through my old aerial. Might be worth a try for £40 or less.
TV reception here is rather poor due to hills so I have been using cable. However I recently bought a simple digital box, and get good reception through my old aerial. Might be worth a try for £40 or less.
The Bel, or more commonly used decibel (dB) is a relative scale only, and pretty much meaningless unless you know the original reference level.
A common reference power level is 1 milliwatt, which is often expressed as dBm0 (power level in decibels relative to a reference power of 1milliwatt = 0 dB)
It is a logarithmic scale. Halving the power level is equivalent to a reduction of about 3 dB, and a tenth of the power is equivalent to a reduction of 10 dB.
So:-
0 dB = 1 mW
-10 dB = 0.1 mW
-20 dB = 0.01 mW
-30 dB = 0.001 mW
-40 dB = 0.0001 mw
-50 dB = 0.00001 mW
-53 dB = 0.000005 mW
-56 dB = 0.0000025 mW
so your level of -55 dB is the equivalent to a signal of about 0.000003 milliwatts.
A common reference power level is 1 milliwatt, which is often expressed as dBm0 (power level in decibels relative to a reference power of 1milliwatt = 0 dB)
It is a logarithmic scale. Halving the power level is equivalent to a reduction of about 3 dB, and a tenth of the power is equivalent to a reduction of 10 dB.
So:-
0 dB = 1 mW
-10 dB = 0.1 mW
-20 dB = 0.01 mW
-30 dB = 0.001 mW
-40 dB = 0.0001 mw
-50 dB = 0.00001 mW
-53 dB = 0.000005 mW
-56 dB = 0.0000025 mW
so your level of -55 dB is the equivalent to a signal of about 0.000003 milliwatts.
The reference level normally used for TV signals is the uV. 60dbuV is roughly the level required for acceptable reception on analogue TV and 45 dBuV for digital TV. So 55 is a bit low for analogue but you should be OK with digital.
I'm in a weak signal area, I have fitted a freeview box and it's was a slightly better picture then went on to fit the DAT 75 Digital aerial and what a difference! I even got one on my summerhouse which is a lot lower and I can see all the freeview channels where I couldn't before
http://www.tlc-direct.co.uk/Products/MXDAT75.html
I'm not even in a freeview postcode area for freeview but not having any problem
I suspect a lot of people are having problems with freeview reception and spending money on new aerial installations in preparation for switchover. What is not well publicised is that when digital switchover happens, all the main transmitters will increase their output power by a factor of 10. For most transmitters the multiplex groups will also all be transmitted in the current analogue channel groups so wideband aerials will not be required. In the meantime, it's good business for the aerial installers!!
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