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DIY Aerial Install

Discussion in 'Audio Visual' started by RichA, 2 Dec 2018.

  1. RichA

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    I am having roof / refurb works done and my aerial has been removed. I need to re-instate whilst there is scaffolding up, and have a few questions.

    1. Can an aerial be mounted by a diy-er (me)? How accurate does the direction have to be?
    2. What is the best type of fixing/method to mount the aerial?
    3. Is my current aerial suitable?
    4. Does the pair of broken fins cause an issue?
    Thanks, Rich

    Aerial_1.JPG Aerial_2.JPG
     
  2. flameport

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    1 - Depends on your capabilities, very if you want it to work reliably.
    2 - Depends on what it is to be fixed to. Chimney, wall, other?
    3,4 - No and being a wideband it was probably never suitable, and now it's broken anyway.
     
  3. Lucid

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    @flameport has covered the basics. I'll fill in a bit of the detail.

    Any DIYer can install an aerial. A fee will do a very good job because they spend the money and time to do it correctly. When that's factored, the DIY job cost more to do than having a pro do the work.

    The biggest question with any DIY install is "What will it cost to put a bodged job right?"

    For chimney installs, wrecked pointing causing water ingress is all too common where a poor bracket has been used or the bracket incorrectly installed. In the worst case I have seen, the cost to make good ran to several hundreds of £'s. This was because they needed a roofer to sort the chimney, then a builder to sort the wet and dry rot in the timber plus fix the damage to the ceilings and walls in two rooms. I know this all sound a bit doom and gloom, and I have to stress that this was an extreme case. However, the home owner thought that putting up an aerial was an easy job and didn't stop to consider that the bracket was too small for the size of aerial. Most times the bracket causes brickwork damage, it's just a bit of repoint in required if caught early enough. But how often do you get on the roof to check the pointing?

    Regarding alignment; depending on the local field strength, there's anything from a 10 to 30 degree arc where an aerial will function. You can get this from simply pointing in the same general diection as the neighbours aerials, but it won't give acceptable results in most cases. The next stage is fine tuning down to a 1-2 degree arc. For that you'll need a meter if you're working solo.

    The pocket aerial meters at £10-£15 are a waste of space. The metered range starts at too high a signal level, and the gradations are too large to provide anything but very coarse directional indication.

    The supposedly semi-pro meters such as the Fringe Pro+ (approx £50) are more accurate, but they still only read an average of all the muxes. You might think "What's wrong with that?" and if all the muxes came in at the same power then an average meter would do just fine.

    What you find in use though is that there's a variation in strength depending on the transmission power, and the frequency, and the alignment of the aerial. In the trade we call this 'Slope'. During an install, I might see anything up to a 6dB spread in signal power before the aerial direction is fine tuned. 6dB is the equivalent of halving the signal, then halving it again. That means the weakest mux can be just 25% of the power of the strongest.

    My professional meter cost around £400, and it shows me a bar graph with each of the muxes represented. As I move the aerial, the levels change. My objective is to minimise the slope difference across the main muxes down to the lowest level. This might not be when the aerial is pointing directly at the transmitter.

    Brackets: For low to medium wind loading aerial on a 2-3m pole then an 8" galvanised mitre cradle will generally be sufficient unless the site is in a very exposed location.

    In summary then, yes a DIY install is possible. However, paying a professional could work out cheaper, and certainly quicker, and most likely with with better results, too.




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    Last edited: 3 Dec 2018
  4. bernardgreen

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    Makes life easy compared to one of the originals, the Lab Craft 415

    labcraft_415.jpg

    I worked for LabCraft when these were one of the best meters available. Calibrating them was a time consuming process.
     
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  5. Lucid

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    Yep. Before my time but I can appreciate the convergence of art and engineering.

    Apparently, aerials were tuned in situ, or so I'm told. Would this have been the 405 line VHF 'H-shaped' aerials?

    Lots of stuff has changed. Some of it in quite a short space of time. From the late 80s through to the mid noughties, CRT projectors were the premium choice for home cinema, and I've converged more of them than I care to remember. That'll take some back to the days when CRT TVs had to be set up for picture geometry. Lol
     
  6. bernardgreen

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    The 415 was UHF, there was another version for VHF

    Being mains powered it had to be at ground ( or other safe ) level so invariably two person job, one tweaking the aerial and one at the meter shouting meter reading.

    and back to when ITV first broadcast commerical TV. Most existing TV sets were single channel and tuned to the local BBC transmitter. To receive ITV a convertor unit took the ITV signal from the aerial and converted it to a strong signal on the BBC frequency and this was fed to the TV at a level that swamped the BBC signal. It was not un-common to be watching ITV with a faint image of the BBC program rolling behind the ITV images. Our neighbour's convertor was an open chassis with two thermionic valves glowing warmly and in full view at the side of the TV.

    Google Earth is useful for getting a bearing to the TV transmitter. Use the Ruler tool to draw a ruler line from chimney stack to the transmitter site. Then zoom in towards the chimney stack and see which house or other landmark are crossed by the ruler line. Then aim the aerial at that landmark.
     
  7. JohnD

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    no need. there is at least one online web tool that, if you tell it your postcode, will tell you the location and orientation of your nearest transmitter, and its bearing from your position.
     
  8. bernardgreen

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    and the accuracy of reading a compass while hanging onto a chimney stack and an aerial and the compass is ?
     
  9. ericmark

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    I loved playing with aerials. However not for TV, they are so cheap just not worth making one your self, however the Yagi is named after the radio ham who designed it, same with HB9CV and many others, most made and designed in first place by amateurs, not professionals.

    As to missing elements likely it still will work, rule of thumb is closer the elements are the narrower the band width is. The whole problem with TV is you need a rather wide band width, so many of the tricks done by amateurs like having 9 aerials connected together to bounce signals off the moon, will simply not work.

    It depends how close you are to the transmitter, here I am low down and to get TV signals my aerial has to be high gain and on the roof, in my old house I could sellotape the aerial to the window, seem to remember around 9 inches for TV aerial. Just used some 300Ω feeder cable on 75Ω coax.

    I did have a rotator and I could get winter hill, moel-y-parc and central, however only because it was handy and had my 2 meter HB9CV on same pole, but so much depends on where you live.

    It use to make me laugh to see these massive aerials being fitted on the house around me, when we could see the lights on the moel-y-parc mast, I use to talk to amateurs through the repeater on the same mast using 5 watt and a little hand held radio, there must have been some very good sales men to sell them such huge aerials.

    Hear only 6 miles from old home and the aerial fitter really earns his money. All down to where you live. Seen many a caravan park with caravans using little omnidirectional aerials all around the site, and site owner has a 24 element beam, clearly again good salesman.
     
  10. Lucid

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    I don't know if I would use the caravaning crowd as a reliable barometer to measure correct aerial choice. They're often motivated by what looks nice or 'neat'. When it comes to spending on the 'van, logic seems to go out of the window. :LOL:

    I've been button-holed a fair number of times asking why their super-duper £139-£179 flying saucer with a billion dB gain can't pick up the local stations in some or other remote and sheltered caravan site. The answer is invariably the same; too little metal in the air, and nowhere near enough pointing at the appropriate transmitter.
     
  11. ericmark

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    Yes I must agree, however there also seems to be reverse with many houses, fit a really big aerial then you can use rubbish coax or run it for miles around the house.

    I love the idea of mast head amplifier, however also see the practical problems, including getting to it for maintenance.

    In old house, either you needed a massive set of brackets on the wall, or fasten it to landers, if using latter wind resistance and weight was very important, so when a 2 element Yagi will do the job, there is no point fitting a 24 element one, it just falls off in the wind, which does not matter that much as moel-y-parc is that close you could receive it on wet string, so even dangling on coax the aerial still works.

    I build (cut and soldered) an aerial from 300Ω ribbon cable in the format of a slim jim, similar to J beam and stuck it to window with selotape, no pre-amp and it worked fine. Would not expect anything else when I can look out of window and see the navigation lights on the mast.

    Yet the local aerial fitter still puts up massive lumps of metal, some times however reception seems to defy all reason, with a rotator I could easy swing aerial around, and on caravan sites after trying to get a signal by pointing aerial using maidenhead locator compass and some maths, I would simply tune to channel and turn aerial, once you got it working, looking in the direction it was pointing one could often see some item like block of flats which was likely reflecting the signal.

    Did it once and found I was picking up porn, seems some one had a video feeding a portable TV with aerial still attached. This same problem has also stopped us getting TV, when winter hill used channel 68 many sky boxes were tuned to channel 68 and would stop reception, moving the aerial just 3 foot left or right could often cure it.
     
  12. RichA

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    Thanks for the advice.

    Has led me to have a rethink; I pretty much exclusively use sky at the moment. Would it be crazy not to have an aerial at all?
     
  13. Lucid

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    It depends how reliable Sky is.

    Despite strong readings for Quality and Strength from both LNB feeds, there have been a few occasions where torrential rain has saturated the mesh dish and disrupted reception.

    More often though, we get a frozen box after Sky dick around with firmware updates. Having the aerial as a fallback is useful.

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  14. bernardgreen

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    Some trains were fitted with GPS to ensure the driver had stopped his train in the right place at the station and was opening the doors on the correct side ( where the platform was ).

    In fog and other adverse weather conditions the GPS failed and because of this doors could not be opened as the GPS in the train had no idea where it was.

    The GPS idea was thrown out and the old fashion method re-installed. A receiver coil on the train had to align with a transmitter coil at the side of the track to give the driver the OK to open the doors.

    But for all I know the GPS method may have been improved and be back in use,
     
  15. Lucid

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    Bit puzzled what GPS, receiver coils and train position have to do with satellite reception and an aerial as a backup???
     
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