Mast head amp (aerial booster?)

Discussion in 'Audio Visual' started by MickyP10, 19 Nov 2021.

  1. MickyP10

    MickyP10

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    Just moved and found one of these in the loft, connecting three tv leads (rooms) to the aerial. None work, however (the outlets), so I assume it's broken. If I connect the tv living room co-ax direct to the aerial and bypass the amp, the tv tunes and finds programmes fine, but no HD channels, so maybe the signal's a bit low (and also why someone thought an amplifier a good idea?)

    So... Q1) Should these have a power supply? All that I've seen do.

    Q2) Can anyone recommend a simple powered or non powered booster for a single (or perhaps two) tv setup?

    Thank you!

    41OgEoAGdML._AC_UY327_QL65_.jpg
     
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  3. Sureitsoff?

    Sureitsoff?

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    that style of amp looks like it is powered via a power supply that feeds up the coax. is there another box near the tv point
     
  4. Harry Bloomfield

    Harry Bloomfield

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    It is not necessarily a booster, it's distribution amp so that more than one TV can run from the one antenna. It needs to have power, as above, check how it was supposed to be powered. Some are powered directly from a socket near the unit, others are powered via the coax and a unit at the rear of one of the TV's. It also has variable gain setting, that may need adjusting to suit your local signal strength.
     
  5. Sureitsoff?

    Sureitsoff?

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  6. MickyP10

    MickyP10

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    Can't find any power supply in loft. It's possible there was one in the living room and it was removed when previous occupier moved out. If it had a power supply here, say, does it boost or power all the aerial leads connected to amp or just the one by power amp in living room? Eg, would it be better to have a power supply in loft by amp/splitter?

    Of course, I don't know if it works at this stage, so any recommendations for decent alternatives would be valued.
     
  7. winston1

    winston1

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    It is very common for people to take the power supply from behind the set when they move. Ask them for it back or buy a replacement. It powers the amp so all outlets will get a signal. I don’t know if the power supply can be fitted at any outlet or a specific one.

    No advantage in fitting the power supply in the loft and you probably don’t have a power socket there anyway.

    Is is not possible to suggest alternative amplifiers without measuring the signal strength at your location.
     
    Last edited: 19 Nov 2021
  8. MickyP10

    MickyP10

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    Thanks all.
     
  9. Lucid

    Lucid

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    If the picture you posted is the same as what you've actually got rather than just the nearest lookalike image, then you've got a phantom-powered 4-way amplified splitter with variable gain. These things need power to work. And I don't just mean some power so that 'boosting' works; I mean power so that any signal will pass through it. Without power you'll get diddly-squat from any of the outputs, so the guys here are correct.

    The reason for installing something that uses a remote power supply with the voltage going up the cable is so that you don't have to have a 240V AC to DC transformer running 24/7 365 days a year that's neatly tucked away out of sight whilst living in a space that gets freezing cold in winter and boiling hot in summer. Some of us installers think that leaving something mains powered and unattended in such an environment isn't the best idea, particularly as a lot of this gear is made in China. I'm not suggesting that the amplifier manufacturing brands themselves would cut corners, but the subcontractors and their suppliers and their suppliers too.... Well, I'll leave you to draw your own conclusions.

    Regarding HD signals, this could be a case of either the signal needing a lift from the splitter because the aerial is no longer a good match for the frequencies being transmitted, or maybe the local transmitter is one of the Light Service ones with limited HD.

    The 'matching' thing is because of all the signal reshuffling to do with 4G and 5G. Over the past couple of decades an awful lot of folk had Wideband High-Gain aerials installed. These tuned from RF ch21 to ch68, but the highest gain was in the upper half of the frequency range; say ch40 to 68. Below ch40 the gain tailed off quite a bit. For someone in an area where the muxes were broadcast in the upper half of the range that was a really good fit. However, for the last dozen years or so the company responsible for the transmitters has been playing musical chairs with the frequencies for our muxes. This is because our Government wanted to sell off part of the TV frequency band for mobile phone use. It started with the sell-off to make space for 4G, so RF channels 60-68 went first. Then, more recently, the 5G sell-off means they rejigged again to sell off ch49 and above. The result is that the muxes are now in the lower half of the old ch21-68 range, and this is where those wideband high-gain aerials don't work quite as well.

    For muxes broadcast on higher power levels and where the homes get a high field strength then they'll get by. Some folk though in more marginal areas could find they lose certain muxes when the conditions are not favourable. This is more likely to be the case where the mux frequency is on a low RF channel number.

    The nature of digital means there's quite a fine line between the signal working okay and total loss. Changing the aerial could be the right thing to do in light of the new distribution.
     
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  11. Harry Bloomfield

    Harry Bloomfield

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    I'll refer you to Lucid's detailed reply, but to answer your question.... Until the distribution unit has it's power supply, there will be no signal at all to any of the TV's. What should work as a temporary fix, assuming the antenna is working and providing adequate signal is....

    If you were to buy a F-plug female, back to back connector /plug, and join the antenna coax (marked IN at the amp), to which ever of those OUT leads goes to your living room TV.
     
  12. Tricky-Dicky

    Tricky-Dicky

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  13. Tricky-Dicky

    Tricky-Dicky

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  14. Sureitsoff?

    Sureitsoff?

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  15. ericmark

    ericmark

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    On one of my TV's it can be set to give an output on the aerial, check before you buy power supply.
     
  16. winston1

    winston1

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    Good point. Though usually this is 5v which may not be enough for some amps.
     
  17. Harry Bloomfield

    Harry Bloomfield

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    Common for sat dish inputs, but I have never come across that on the terrestrial antenna socket, though I did wonder if that might be a possibility. To work and allow other sets on the other outputs to get a signal, it would need to be able to be set to always on, even when that TV was off.
     
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