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Digital TV signal boosters

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Tom M:
I have recently moved into a rental place and using a TV with built in freeview tuner running of a normal roof aerial using co-ax. The signal doesn't seem that great though as will 'find' the channels when I do the scan, but won't necessarily be able to watch them as the signal is not sufficiently strong.

Have seen various signal-booster type devices available, some plug into the mains, some don't. The question is though, do they actually work? And how exactly are they supposed to work?

Is the tuner within the TV likely to have any influence over the strength of the signal too? Am likely to get a PVR box thing soon too (Humax or similar) so would this have a better chance of receiving the channels better?

Pickled Onion:
Yes they work, no idea what they actually do*. You're unlikely to see any difference in tuning ability between the telly and the PVR.



*surely if the signal can be boosted for a couple of quid's worth of components, the TV manufacturers would put the same thing inside the telly tuner? Apparently not.

Kim:
They're just amplifiers.  They amplify everything, including the noise, and add their own helping of noise for good measure.

What they're supposed to be used for is to amplify the signal to make up for long cable runs or splitting it between multiple receivers.  This is a perfectly valid thing to do, and you only need an amplifier with a modest amount of gain to achieve it.

What they actually tend to get used for is to compensate for inadequate aerials and/or crap cable.  A higher gain (ie. more directional) aerial gives you more signal without adding additional noise, improving the signal to noise ratio.  An amplifier won't do this (indeed, if anything, it will reduce the SNR) but sometimes a little bit more signal is just enough to make the difference between usable reception and not.  Particularly with the all-or-nothing behaviour of digital broadcasting.


As with all things, the quality and behaviour of tuners, amplifiers, aerials and cable vary.  Don't underestimate the ability of cheap (invariably brown) coax with skimpy shielding that's been out in the rain for 20 years to waste perfectly good signal.  Similarly, don't underestimate the ability of impressive looking wideband aerials to be crap; they're engineered to sell aerials, not pick up radio signals.  And never underestimate the ability of  a) builders  b) electricians  or  c) Sky installers to cock up installations through general cheapness or ignorance of RF.


One potential gotcha, particularly in rented accommodation:  Sometimes it's deemed necessary to put an amplifier right at the aerial.  This is powered by DC sent back up the coax, in the same manner as the LNB on satellite dishes.  The power supply for a masthead amplifier looks indistinguishable to the untrained eye from a signal booster (it being a generic box that plugs into the mains, is connected inline with the aerial and makes the reception better).  The main difference being that a power supply won't do much to amplify a signal, and an amplifier won't do much to power a masthead amplifier - and an unpowered masthead amplifier won't give you much in the way of signal.

Squinting at the aerial with binoculars to see if a previous tenant has run off with a masthead power supply left as an exercise for the reader...


Also note that all the RF engineering in the world won't make the programmes any better, unless you're on the Lincolnshire/Yorkshire border and a sufficiently sensitive setup will allow you to avoid Peter Levy.

Biggsy:

--- Quote from: Tom M on 26 July, 2016, 03:41:33 pm ---Is the tuner within the TV likely to have any influence over the strength of the signal too?
--- End quote ---

Some tuners are more sensitive than others (can work with weaker signals), but it depends on the exact products rather than type of product.

aidan.f:
Wot Kim said is right, but we should add intermodulation products as another unwanted output from amplifiers.

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