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  1. #1
    Naf
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    Default TV reception probs - digital

    Hi all,
    Our tv reception keeps dropping out, most of the time it's OK but somtimes channel 10 and 9 are crap, other channels do it also but not as bad. It's a plasma tv. Just wanting to know what are the usual areas to look for problems. It doensn't matter if it's windy or raining, however it seems to happen when I want to watch something, and it's really p...ing me off. I bought a plug in booster thingy from bunnings the day before the grnad final, the reception was great but then a few days later it went south again.
    Also in regards to this, when a light anywhere in the house is switched on or off it pixelates the tv for a second, we have a battery operated smelly spray thing that srays every 15 minutes or so that does the same thing.

    Thanks
    Nathan

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    Have you got an outside antenna, I had to move the direction of mine slightly to get a perfect signal...compared to the old TV...might help.

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    The booster is probably causing that. Have you tried without the booster, ie; completely by passing it - don't just switch it off with all the coax still plugged in?
    A booster will only amplify the signal you have available. I once remember hearing that. If you have bad reception, it will only amplify your bad reception. Don't know how true that is, but it sounds good.

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    Quote Originally Posted by tricky4000 View Post
    A booster will only amplify the signal you have available. I once remember hearing that. If you have bad reception, it will only amplify your bad reception.
    Quite true.

    The amplifier can only amplify the signal coming in to it. If the incoming signal has a poor signal-to-noise ratio, the output will also have a poor signal-to-noise ratio.

    Boosters are designed to:
    (a) boost the signal for splitting (driving multiple points) or
    (b) to overcome cable losses.
    In the case of the later, it is better if the amplifier is close to the antenna.

  5. #5
    Soldiers Earned Your Right To Free Speech watson's Avatar
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    Quote Originally Posted by Naf View Post
    Also in regards to this, when a light anywhere in the house is switched on or off it pixelates the tv for a second, we have a battery operated smelly spray thing that srays every 15 minutes or so that does the same thing.

    Thanks
    Nathan
    G'day Nathan,
    you must be pretty far off the correct antenna postioning if the lights and the poofer spray are interfering. Antenna check and sighting would be good.
    Last edited by watson; 2nd Oct 2009 at 03:26 PM. Reason: Wrong Idea

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    hi,

    great a tv thread, bought a standard set-top box the other week and cannot get Channel 10 at all, never, do re-scan a 100 times

    is a new antenna required? reside in Prahran

    cheers

  7. #7
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    I live so close to the TV towers that the signal strength is overboard, I currently have a $42 internal antenna, has gain control, AC powered, I don't use the AC power

  8. #8
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    Quote Originally Posted by myla View Post
    hi,

    great a tv thread, bought a standard set-top box the other week and cannot get Channel 10 at all, never, do re-scan a 100 times

    is a new antenna required? reside in Prahran

    cheers
    Myla, does channel 10 show up in your channel list?
    Channel 10 and One (sport) are the worst of them when it plays up, last night the only channel watchable was sbs, so I had to watch a show about the vatican, That's not very exciting for an atheist. That's my plan for today, fix tv antenna.

    Nathan

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    hi,

    no, it never finds 10

    all others perfect

    thanks

  10. #10
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    Is there a way you can manually put the settings in for channel 10? I have little knowledge of these things so I'll let someone with experience in this field help you out.

    Nathan

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    OK, now the picture is fine, there are no errors and signal strength is just over 50 out of 100. when it goes crap the errors range from 6 or 8 out of 10.
    Very frustrating.

    Nathan

  12. #12
    rrobor
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    Several things you can do. First the cable from the antenna must be the best. Its fairly hard and does not take well to being continuously bent so lock it down . Connections must be done correctly, a slightly dodgy coax plug can loose heaps as can cheap cable. Amplifiers! What was stated before is not correct. The front end of your tuner is an amplifier so amplifiers help. But the amplifier should be a masthead type not some form of gungey splitter amp. Amplifiers are the last resort as stuck up there they are subject to static and a good lightning storm can kill them The power runs up the cable from a supply inside. Coax cable is also a favourite toy for Cockys to peel. The cable from your antenna should go up before turning to come down. This is to stop water if it gets into the box. So fit a masthead amplifier on a quality antenna, if that does not fix, you can fit another in tandem. I have worked on an antenna with 3 tandem masthead amplifiers, That was on a school in the Ciy of Dunblane, Scotland.

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    Most analog TV's (CRT) require between about a 50dB & 75dB signal for a good picture. Anything less than 50dB is likely to give a snowy picture. Anything higher than 75dB is likely to give a herring bone pattern on the screen. I don't know what the minimum & maximum dB requirements are for digital signals on digital equipment.
    The bigger the telly, the more dB's are required.

    A Masthead Amplifier is only used if the signal from the antenna is low (no less than about 25dB & up to about 45dB/50dB).

    Baluns are a common problem...they get old & fail. If you have splitter boxes, they could also be a problem.

    A good system will use "F" type connectors & good quality RG-6 coax.

    Since you probably don't have a dB meter (a very expensive signal strength meter), it may be best just to call the local antenna guy.

    Oh yes & as rrobor said, connections can be a HUGE problem.

  14. #14
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    The voltage of a TV signal from the antenna is measured in microvolts. The bell is a measure of losses in a system and was the loss recorded (from memory) of an electrical signal along one mile of standard telephone wire. So to measure in decibells you need a fixed reference point. Overload usually causes an unstable and slightly over contrasted look in analogue TV . In digital it can cause pixilation. The major problem with TV reception is 2 things. 1/ people like me telling customers your antenna is faulty, they go out and get a bigger better antenna and leave a black hole for their neighbour. The fix should have been for the transmitter to increase power. And 2/ UHF is line of sight. The lower the frequency used the more the signal would flow with the contours of the ground or as a sky wave. Go to high frequency UHF and the signal becomes more directional. Anybody brought up in Scotland must remember Radio Luxenburg, That beamed in at night as a sky wave, You couldnt get it during the day as the sun pushed atmospheric belts down, at night they lifted and mirrored the signal north. UHF there would shoot directly on and out.

  15. #15
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    The reception definately seems worse at night, usually, I got up on the roof yesterday and moved the antenna a bit. Got the reception upto 80 out of 100, got off the roof and it was back to around 40, however there were no bit rate errrors at all and the picture stayed perfect until late last night when the errors started again.

    Nathan

  16. #16
    rrobor
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    Try cleaning the antenna. Not the rods and things but the connections. Not knowing what you have Ill explain a combo VHF UHF. At the front you have a UHF section, arms roughly about 300mm. You will have a few reflectors in front then the antenna then a deflector next is VHF chans 5A to 10 just bigger arms but same as UHF then the chanel 0 to 4. Between the antennas there are 2 straps usually aluminiunm tubing with alloy bolts. Take these bolts off and polish the oxide off the rods and bolts. If the bolts break replace with brass. The balun on the antenna clean that , make sure the earth is correct. What burb are you in, can you see the Dandenongs. If this dont work get a better antenna. Avoid using franchise antenna installers. I have seen great work from some and rubbish from others so its a lottery.
    Personally by the sound of your problem you are in a reasonable area but your antenna system is poor. Post your suburb and I can tell you more.

  17. #17
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    I'm in Melton South, can't see the Dingdingdongs from where we are. There's a few really big trees that are in direct sight, maybe 50m away. The antenna was in line with the other ones I could see, I've moved it a fraction and the reception got a little better, but it still goes haywire occasionally.

    Nathan

  18. #18
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    Melton South is a good reception area, you should be able to get a top quality picture with a reasonable antenna there. DO NOT use a masthead amplifier there. Melton at one time was one of the areas I fixed in and on average we got one TV a year blown up by lightning, mainly though West Melton. So amplifiers are 1 not needed and 2 liable to be killed. Trees at 50 metres are not an issue. Chances are you have crap cable or bad connections. You have a nice big Bunnings there get the best cable, its usually black and quite stiff and run it with as few joints as you can. To test how good your reception area is, get a video lead, plug it into the TV, get your car keys and touch the centre pin of the video lead, If you get a reasonable picture your area is good.

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    Nobody can really give any advice unless the following is known;

    1] exactly what antenna you have (take a good photo).
    2] your exact location.
    3] when the antenna & all cabling was installed.
    4] if you use splitters, how many do you have? What type are they? 2 way, 3 way or 4 way splitters? Were they installed at the same time as the system?

    Most antenna installers use decibel (dB) meters, which are very expensive. These devices make it easy to install & "fault find" a system.

    Usually at night, signal strength increases (VHF/UHF). If you are experiencing problems at night, it could be due to too much signal. The only way to tell is with a dB meter.
    I strongly advise you call an antenna installer otherwise you could be buggerising around for ages.

    Some typical problems;

    1] old & corroded antenna (including balun).
    2] connections.
    3] birds & such like.
    4] old or damaged cable (water damage included).
    5] faulty "fly leads". The lead that runs from the wall socket to the TV.

  20. #20
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    Please Most antenna installers use a signal strength meter which measures in millivolts. As explained before a decibell which is 0.1 of a bell is a logarithmic measuring scale for measuring gain or loss in logarithmic comodities like sound waves. It is based on the loss along a cable. For example if you feed 10 V into a cable and after 1 mile you have 5V after 2 miles you will have 2.5V and 3 miles 1.25V. In the logarithmic scale a loss of 3DB is half the signal so if your starting point was 20 then plus 3db is 40 and minus 3db is 10. A picture of an antenna tells little, If it points incorrectly the best antenna is useless. The guy put this up himself he has no splitters, and his area is good reception, I serviced that area for 15 years. Usually a wet piece of string would work there thats why I suspect his cables.

  21. #21
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    Hi, sorry but I didn't install the antenna, it was already there when we moved in. The reception was fine for a couple of months, just seems to be getting progressively worse. And I should have mentioned it does have a splitter, it's on the antenna mast, then one cable goes to the lounge and the other goes to the bedroom. I didn't know it had a splitter until I went onto the roof, I should have realised though seeing as theres a cable going into the bedroom

    Nathan

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    2K Club Member chrisp's Avatar
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    Nathan,

    Do you have something plugged into both outlets?

    The reason I ask is that an unterminated line (i.e. a output from a splitter with nothing connected) can cause reflections or act as a tuned stub (and depending upon the length of the stub, these can act as filters to certain frequencies e.g. maybe digital 10?). Unused outlets are supposed to be terminated (but rarely are) with a 75 ohm terminator to prevent reflections and standing waves. Plugging in a video or TV will also serve the purpose of a terminator.

    Also, I think it would be helpful to back up a bit with the problem.


    • I assume the antenna was originally used for analogue television reception. If so, did it work okay on all channels? Was SBS okay? If the reception was okay on analogue SBS this would indicate that you have some UHF reception.
    • Has the antenna worked for digital reception in the past or are you setting up a digital system for the first time?
    • Are you having trouble trying to receive HD digital 10 or SD digital 10?

  23. #23
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    chrisp, there an anologue tv plugged into the bedroom cable and a plasma in the loungeroom. We bought the house 6 months ago, I remember the previous owners son had a plasma tv when we came through the house, but I think he was stoned a lot so he probably didn't notice any problems, he actually offered me a bong on settlement day.
    Channel 10 is definately the worst of the lot, just checked it again now, everything looks OK, no errors. CH10 is on about 40 out of 100 reception, CH9 is around 60, CH7 is around 80, CH2 is around 45 and SBS is around 30. It's only when the bit rate errors start, thats when the reception is crap, even on the anologue tv you can see it goes a little .. well different, still watchable but it has sorta little static spots/lines on the screen, but not all over, maybe 1/4 of the screen. Its sorta like morse code on my tv, you know dots and dashes. Now I'm starting to sound loony, it's the nightshift. Hopefully you know what I mean.

    Nathan

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    I dont know where crisp is coming from but the begger knows his stuff, I have no arguement with that. I think you now have a good idea as to what is your issue. Split the cable and thats 3DB gone. Now 3DB is half signal. But if you had a picture on analogue that was just on snow, 3DB you would just notice a difference. Do you need that spur? Is it worth it. In Melton S I could cut a good antenna 2 ways and get 100% and have no issues, Melton S is lower than the Dandenong transmitters by a long way and Melton South is a pancake with undulations till the towers.

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    OK, I'll get rid of the bedroom connection and see what happens. I may do it tomorrow, see how I feel when I get up, otherwise it'll have to wait until I finish this block of nights, Thursday week.

    Nathan

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    I live a stone throws distance (albeit a long stone throw) from Dandenong mountains and can clearly see the towers from my roof. So reception isn't an issue at all.

    A work mate lives "in the shadows" of the towers, literally directly undernearth them and he has zero reception. The irony.
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  27. #27
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    Please dont get evereybody incorrect, If you have a splitter then regardless of what is working , your signal is split 2 ways. To Goner its known us umbarella effect. As to the bong, think you\rself lucky he didnt try to sell you his chemestry set for producing God knows what. Guess where you moved to.

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    Quote Originally Posted by chrisp View Post
    Nathan,

    Do you have something plugged into both outlets?

    The reason I ask is that an unterminated line (i.e. a output from a splitter with nothing connected) can cause reflections or act as a tuned stub (and depending upon the length of the stub, these can act as filters to certain frequencies e.g. maybe digital 10?). Unused outlets are supposed to be terminated (but rarely are) with a 75 ohm terminator to prevent reflections and standing waves. Plugging in a video or TV will also serve the purpose of a terminator.

    Also, I think it would be helpful to back up a bit with the problem.


    • I assume the antenna was originally used for analogue television reception. If so, did it work okay on all channels? Was SBS okay? If the reception was okay on analogue SBS this would indicate that you have some UHF reception.
    • Has the antenna worked for digital reception in the past or are you setting up a digital system for the first time?
    • Are you having trouble trying to receive HD digital 10 or SD digital 10?
    hi crisp,

    yes, i dont get SD digital 10 at all, never since i got set top box, have tried search manually and still zip

    live in Prahran, all other channels fine also i get all channels on analogue

    any advice

    thanks

  29. #29
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    Prahran is a different kettle of fish to S melton. There are some areas where reception is very bad and regardless of what you do it will not improve. Now I havent worked that area for a few years now but there was a relay built on top of the Jam factory. From memory the polarisation was different to the Dandenongs, it was vertical. So if your reception is crap where are you getting it from, it might pay you to have an expert in who knows that area.

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    hi,
    reception is fine

    on analogue all channels great

    on digital all channels great, except get no ch10 at all

    wouldnt have a clue what to do next

    thanks

  31. #31
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    Digital is tough because in digital you have 2 states only, Yes or no. In analogue you can see the good , the bad and the indifferent but in digital its there or its not. How good are the rest, we have no idea, the only way there is to find out is toget someone with a signal strength meter to measure the actual signal.
    There used to be a guy in Armadale who was the bees knees in Antennas but thats back a few years now.

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    Reception just started to play up now 19:55. Here's a pic of the splitter on the pole.
    Attached Thumbnails Attached Thumbnails 100_2103-2.jpg  

  33. #33
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    No one can tell what that is. I would suspect its a diplexer separating a VHF from a UHF antenna but thats a guess, ask the kangaroo spanish kid.

  34. #34
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    updated pic with artistic modifications
    Attached Thumbnails Attached Thumbnails 100_2103-2.jpg  

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    Here's a stab in the dark. Could it temperature related? Perhaps something is *just* touching and when it gets cold it moves.

    *shrug*
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    I think first I'll remove the bedroom connection and see what happens, hopefully tomorrow. If that doesn't work then I'll maybe get someone out to test it, my only concern is that it only goes bad in the evening and I'm sure no one wants to come and test it that late. Surely they could tell anyway no matter what time they test.

    Nat

  37. #37
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    If thats true your antenna was installed by a nutter. Why put a vulnerable box out in the elements when you could put it inside the roof. If this is part of the job then the rest will be the same. Sorry remove the cable and start from scratch. It looks like a Mrs Ariel job so the antenna may be crap as well. My mate fits Antennas and swears by their ariels, says their the best for growing peas up and he gets a lot of them for his peas.

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    Quote Originally Posted by rrobor View Post
    Please Most antenna installers use a signal strength meter which measures in millivolts. As explained before a decibell which is 0.1 of a bell is a logarithmic measuring scale for measuring gain or loss in logarithmic comodities like sound waves. It is based on the loss along a cable. For example if you feed 10 V into a cable and after 1 mile you have 5V after 2 miles you will have 2.5V and 3 miles 1.25V. In the logarithmic scale a loss of 3DB is half the signal so if your starting point was 20 then plus 3db is 40 and minus 3db is 10. A picture of an antenna tells little, If it points incorrectly the best antenna is useless. The guy put this up himself he has no splitters, and his area is good reception, I serviced that area for 15 years. Usually a wet piece of string would work there thats why I suspect his cables.
    When I installed antennas in Sydney about 13 years ago (for a previously well known Sydney company - they don't exist now), only analog systems were used. The FS meter used (moving coil type) gave the results in dB (obviously voltage related).

    The digital TV world appears to be vastly different to "the old analog days". Still, most antenna installers base their calculations on losses (dB losses).

    The attachment is an extract from Powered by Google Docs
    Attached Thumbnails Attached Thumbnails digital-tv.jpg  

  39. #39
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    Quote Originally Posted by rrobor View Post
    I dont know where crisp is coming from but ...
    What I'm trying to find out is how well the antenna is working across the frequency range.

    Some (most?) digital channels are in the UHF band hence my question as to how the analogue SBS is.

    SD channel 10 is broadcast on the old analogue channel 5 (I think, but could be wrong), but the HD channel 10 is broadcast on channel 50 in the UHF band (same proviso as before ).

    For Nathan to receive HD channel 10, the antenna (feeder, splitter, etc) needs to the workable/useable in the UHF band.

    My "poor mans guide" to antennas is to walk around your neighbourhood and see what is the common antenna installed in your area (and also note the direction they face). You can usually spot the newer antennas - and these are the ones you should look at. Also, if you are on good terms with your neighbours, ask them about their TV reception.

    From rrobor's comments (and I trust his comments), I'm confident that you are in a good reception area, so either you have an old antenna with little useable UHF gain, or (as rrobor has pointed out) it is a feeder (cable) problem.

    BTW, most of the newer wide-band (VHF & UHF) antennas have two distinctively different sets of dipoles (where the cable is connected) - the longer set is the VHF set (with slightly shorter "directors" in the front of it, and longer "reflectors" behind it); the (much) shorter dipole is the UHF set (again, with slightly shorter "directors" in the front of it, and longer "reflectors" behind it. Some even have a "V" shape section as the reflector).

    If the antenna is reasonably new/modern, it might be easiest to just replace the feeder (cable) and leave the splitter out (i.e. just connect it to one TV) and see if the reception improves. I'd even just try a temporary rig up of running a cable directly from the antenna to the TV (don't worry about wall plates etc.) If the reception improves out of sight, then look at reinstalling the cable neatly and perhaps adding a new splitter to the other room.

  40. #40
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    Quote Originally Posted by myla View Post
    hi crisp,

    yes, i dont get SD digital 10 at all, never since i got set top box, have tried search manually and still zip

    live in Prahran, all other channels fine also i get all channels on analogue

    any advice

    thanks
    Hmm, I'm not sure. Inner city areas can be prone to ghosting (in analogue) but this may have different results on digital reception.

    It could be worthwhile having a look at DTV Forum Australia - Australia's Leading Digital TV and AV Forum (Powered by Invision Power Board) and seeing what has been posted there.

    It is interesting that channel 10 is causing so much grief.

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    Another couple of stabs in the dark - from that picture, it looks as though perhaps the cable for the bedroom has a compression type Fconnector, whilst the lounge has a crimped Fconnector. Crimps are a lot easier for the non-professional to do...
    I'd also suggest that the crimped connection looks a tad corroded? And could perhaps be replaced anyways.
    As Rrobor pointed out, these splitters aren't renowned for performing well when exposed to the elements.
    If the connection only goes bad in the evening, it could be that either dew/temperature drop is making a borderline crimp go bad, or it could be the splitter itself.

    I'd start by getting someone to re-do that crimped cable.

  42. #42
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    Quote Originally Posted by elkangorito View Post
    When I installed antennas in Sydney about 13 years ago (for a previously well known Sydney company - they don't exist now), only analog systems were used. The FS meter used (moving coil type) gave the results in dB (obviously voltage related).

    The digital TV world appears to be vastly different to "the old analog days". Still, most antenna installers base their calculations on losses (dB losses).

    The attachment is an extract from Powered by Google Docs
    DB is a loss in cable as stated before but it is not signal strength. You can have a cheap meter which has a mean then it increases or decreases in strength in DB but thats like a volt meter reading 240V as the mean then a DB range above and below. All it is is a crude bar graph. Also as the DB range is logarithmic its not a great way to look at signal strength. As 3 DB is half below and double above the mark. seen on a graph it would be an increasing curve

  43. #43
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    I think elkangorito is referring to dBm (dB milliWatt)

    This is a signal strength or power level measurement (ie. 0dBm = 1mW) into a terminating load. Negative dBm just means less than 1mW

    dB is more a ratio (as rrobor pointed out) for loss or gain of signal.

    There are hundreds of reasons why you can get bad reception as most people here have pointed out.

    I had the same problem, so replaced all of the cable and connectors (water proofing any outside connectors with self amalgamating tape). This helped a lot, but wasn't perfect and still had the problem of random pixelation and when anyone would switch a light or anything else on.

    I ended up finding that i had "dirty" power (small random surges) every now and again.

    The thing that solved it was getting a small UPS (uninterruptible power supply) / conditioning filter off ebay for the set top box and tv (and computer).

    Hopefully this might help.

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    ......forgot to add, make sure any signal cable is well away from any power cables........and, that a lot of digital set top boxes or tv's can block a signal if it is too "hot" (large) it can even just be one channel.

    It might even be worth trying an inline attenuator (3dB, 6dB or even 9dB) if nothing else works.

  45. #45
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    It'll have to wait to be fixed, got the man flu

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    Change the cable, top to bottom, S Melton is 60 odd K away from the transmitter so its not excess signal. Its that stupid splitter and the deterioration around the connectors. With seeing a stupidity like that means the guy fitting it didnt know his trade, so you could have more problems. But one thing for sure it will only get worse.

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    Wierd. The last 2-3 days I have been sick, couldn't do anything except lay on the couch, couldn't even go to work, which is saying something as I do more at home than I do at work (never ever trust a security officer that says they're busy ) Anyway the bloody tv worked perfect the whole time, until about 02:00 this morning. If I find the energy I get up on the roof and have a look at taking the 2nd connection off, see how that goes before running new cable.

    Nat

  48. #48
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    I can now give you about a 90% certainty that its moisture getting into the cable, It will be sucking in by capilliary action on these joints on that silly box.

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    Took the antenna down the other day and removed the bedroom connection and removed the splitter. The picture improved with the antenna still sitting on the ground. Once I put it back up the recption was showing around 60 out of 100 for channel 10 and ONE, all the other have improved also, the lights and smelly sprayer thingy don't interfere with the reception anymore. Oh and the anologue tv in the bedroom still has reception thats better than before, even though I've disconnected it from the antenna.
    Thanks everyone for your help.

    Nathan

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    Quote Originally Posted by rrobor View Post
    Digital is tough because in digital you have 2 states only, Yes or no. In analogue you can see the good , the bad and the indifferent but in digital its there or its not. How good are the rest, we have no idea, the only way there is to find out is toget someone with a signal strength meter to measure the actual signal.
    There used to be a guy in Armadale who was the bees knees in Antennas but thats back a few years now.
    So true, and when analogue gets switched off, those of us whose job it is to fix poor digital tv reception, are going to lose a useful (albeit superficial) initial indicator.
    On the subject of digital signal, there's more to it than just pure signal strength - or signal power as the case is for digital. Noise margin and bit error ratio (BER) play a far bigger role.
    Glad the OP got his problem sorted.
    Regards,
    Michael

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