I agree with everything except the necessity for an amplifier. The amplifier only overcomes the cable losses to the TV , it does not improve the efficiency and unless it is a really big boat or really tall mast, or you are splitting the signal it is not necessary and because the amplifier has a " noise factor " itself, it can actually make the signal worse if the noise contributed is greater than the cable loss that has to be compensated by the amplification in the TV tuner.
Not to overwhelm anyone with tech speak, but there are some times when an amplifier can be usefull, so I wouldn't dismiss their use quite so quickly. I can easly see a cable run of over 20 feet on a lot of boats.......Arctic Traveller*
<h2>Signal Amplifiers, Preamplifiers</h2> Many people think that connecting an external amplifier to the antenna will improve the performance of the antenna.This is usually wrong.Receivers always have more gain than is necessary.(The receiver has an Automatic Gain Control
circuit, AGC, which will reduce strong signals.The AGC makes all stations the same strength at the demodulator.When you add a preamplifier, the TV receiver lowers its own gain, usually by an equivalent amount.)
Normally the signal to noise ratio will be set by the receivers first transistor.But if an external amplifier is added, the first transistor in that amplifier determines the S/N ratio.(Since the external amp will greatly magnify its own noise as well as the signal, the receivers noise becomes insignificant.)Since there is no reason to think the external amps first transistor is quieter than the receivers first transistor, there is generally no benefit to the S/N ratio from an external amplifier.
But an external amplifier will compensate for signal loss in the cable if the amplifier is mounted at the antenna.Without this amplifier, a weak signal, just above the noise level at the antenna, could sink below the noise level due to loss in the cable, and be useless at the receiver.
RG-6 will lose 1 dB of the signal every 18 feet at channel 52.For a DTV channel, 1 dB can be the difference between dropouts every 15 minutes (probably acceptable) and every 30 seconds (unwatchable).This author recommends a mast-mounted amplifier whenever the cable length exceeds 20 feet.(If you are in a good-signal area or you have no high-numbered UHF channels, you can to an extent ignore this advice.)
The preamplifier should have a gain equal to the loss in the cable (for your highest channel) plus another 10 dB (to keep the receivers first transistor out of the picture).
The amplifier can usually exceed this target by another 10 dB without causing trouble.
(If you follow the above rule, the cable length becomes irrelevant, and reducing the cable length yields no benefit.)
When figuring the cable loss, be sure to include the loss in any splitters and baluns.If a 2-to-1 splitter were 100% efficient then you would figure a 3 dB loss since each TV gets half of the power.But splitters are usually 80% to 90% efficient.
2-to-1 splitter3.5-4 dB
3-to-1 splitter5-6 dB
4-to-1 splitter7-8 dB
75W-to-300W balun0.2-2 dB(a balun
is an adapter)
The antenna and the amplifier both have gains measured in dB, and some people add these two numbers (and then maybe subtract the losses) to find the strength of the signal at the receiver.But this sum is worthless.The net gain in front of the amplifier should always be kept separate from the net gain that follows.
You might not need an amplifier if the antenna is too big.But an amplifier can never make up for an antenna that is too small.
<h2>Receiver noise</h2> Actually there is a reason to think the external amplifier is quieter than the receiver.Long ago designers made an effort to make the TVs first amplifier stage very quiet.But now 90% of homes use cable or satellite boxes (strong sources) and most of the rest are rural homes using antennas that have mast-mounted amplifiers.So the TVs noise is rarely a factor.Some TV makers no longer put any effort into making their sets quiet.
Suppose you live in an apartment 15 miles from the transmitter.Your indoor antenna mostly works, but you are troubled by dropouts and some snow appears on analog channels.Will adding an amplifier right at the TV improve things?Yes, if it is quieter than the TV.Unfortunately TV makers see no reason to publish the noise figures for their receivers.So buying an amplifier for an indoor antenna is a total crapshoot.This author recommends that you try a Channel Master Titan or Spartan amplifier, but make sure you can return it if it is no help.