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Thread: Different TVs in marginal signal area

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    Default Different TVs in marginal signal area

    I've moved house and now live in a dodgy area for TV reception. I think the previous owners just watched Austar - there's a satellite dish on the roof and the power supply for the TV masthead amp was missing in action.

    The strange thing is that the reception is perfect on a three year old Sony Bravia TV, but regularly drops out and goes pixellated on other TVs - sometimes for no apparent reason, but also every time an aeroplane goes overhead. The "bad" TVs are a Sanyo, a Grundig and a PCIe TV tuner card. Has anyone else seen this - a TV that, despite a masthead amplifier (so it's not due to a more sensitive / low noise RF front end) blows others out of the water when it comes to coping with a bad quality signal? Are some TVs just much better than others at processing a poor quality signal?

    By way of background, I'm in Launceston, Tas and am about 30km from the Mount Barrow transmitter site (band V, channels 41-45). Most channels aren't too bad, but Southern Cross seems to put out a weaker signal and is much worse to watch. There's a 10m high tree covered rise a few hundred metres away from my house - between the house and the transmitter site, so no line of sight. There's also a community FM transmitter about half a km away. The aerial is a Fracarro log periodic - probably eight years old. There's a masthead amplifier and a three way splitter.

    Things I've tried: I've replaced the wide-band masthead amp that was already here with a Kingray MDA20U (UHF only, has a high pass filter to avoid problems from the FM transmitter). Replaced the coax from the aerial to the masthead amp and to the splitter with good quality RG6. Replaced all the crusty old PAL connectors with F type connectors. I had a spare Fracarro aerial, so I put that up there. I've tried it without the masthead amp (much worse) and with a 6dB attenuator in line with the masthead amp (not much difference).

    I'm starting to think that it's very close to working reliably on all the TVs. It just needs a few dB more signal or a bit better multipath rejection. Maybe an aerial with a bit more gain and a better front to back ratio might make reception reliable. Other than that, I could replace the Sanyo TV with something better - like another Sony, but I'd rather avoid spending that much money if I can avoid it.



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    Phased array antennas generally perform better with diffused signals.

    Antenna mounting location can also be critical.

    Signal quality is what counts.

    You need to be able to measure BER/MER to determine which antenna and mounting location will provide reliable reception.

    A masthead amp will not necessarily improve poor BER... only low signal level, so if you feed poor signal quality into an amp, it will usually only give you a 'louder' poor signal out.

    The key is capturing good signal quality with the right antenna, mounted in the best-possible position.

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    Quote Originally Posted by shred View Post
    I think the previous owners just watched Austar
    They may have used VAST for free to air TV

    Quote Originally Posted by shred View Post
    The strange thing is that the reception is perfect on a three year old Sony Bravia TV, but regularly drops out and goes pixellated on other TVs - sometimes for no apparent reason, but also every time an aeroplane goes overhead. The "bad" TVs are a Sanyo, a Grundig and a PCIe TV tuner card. Has anyone else seen this - a TV that, despite a masthead amplifier (so it's not due to a more sensitive / low noise RF front end) blows others out of the water when it comes to coping with a bad quality signal? Are some TVs just much better than others at processing a poor quality signal?
    Without knowing the mechanism behind your poor reception (poor error rate, multiple reflections), I have also found different models of televisions vary in their response to poor signal, that probably relates to the way the digital signal is processed internally. In my experience, SONY, Panasonic, LG & Samsung are pretty good performers.

    Aircraft travelling overhead can cause momentary disruption to received signals by reflections from their metallic bodies.

    Quote Originally Posted by shred View Post
    Most channels aren't too bad, but Southern Cross seems to put out a weaker signal and is much worse to watch.
    Mt Barrow is one of the most powerful TV transmitters in Oz. This can give rise to problems if signal from the wanted direction is not as strong as a signal being reflected off some feature on the terrain that is impacting on your receiving antenna, and causing problems with the decoding circuitry in the digital television receiver.

    If anything, 41 ABC seems weaker than the rest, based on the installs I do. (I noticed an interesting effect after band restack, the commercial channels, in areas of poor reception, sometimes either required an antenna change, or relocation of an existing TV antenna to restore reception.)

    Which leads me to comment that in a poor reception area, the type & location of the antenna, allied with the correct choice of masthead amplifier, can be critical to good performance, if this is indeed possible.

    Quote Originally Posted by shred View Post
    I've replaced the wide-band masthead amp that was already here with a Kingray MDA20U (UHF only, has a high pass filter to avoid problems from the FM transmitter).
    The FM transmitter wouldn't be a problem with a UHF only masthead amplifier. The one you have will pass UHF CB frequencies & also 700Mhz LTE frequencies, & may overload the amplifier & cause problems should transmissions on these frequencies occur close by.

    Quote Originally Posted by shred View Post
    I've tried it without the masthead amp (much worse) and with a 6dB attenuator in line with the masthead amp (not much difference).
    That kinda suggests to me you do need the masthead for good reception, using a 6dB attenuator would not have much effect on the output side, but probably would be quite noticeable on the input side to the amplifier. Leave it out.

    Quote Originally Posted by shred View Post
    Replaced the coax from the aerial to the masthead amp and to the splitter with good quality RG6. Replaced all the crusty old PAL connectors with F type connectors.
    Always a good move, along with f connect splitters, wall plates & RG6Q flyleads.

    Quote Originally Posted by shred View Post
    I'm starting to think that it's very close to working reliably on all the TVs. It just needs a few dB more signal or a bit better multipath rejection. Maybe an aerial with a bit more gain and a better front to back ratio might make reception reliable.
    I've already commented on choice & location of antenna. While you may be able to luck it by plonking a TV antenna in various spots, without some kind of measuring instrument (and the ability to read & interpret the results), it could be difficult.

    Quote Originally Posted by shred View Post
    the reception is perfect on a three year old Sony Bravia TV
    What does this TV show on the signal information screen, say for Southern Cross & SBS? (usually under something like Settings/Product Support/System Information/Signal condition)
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    Thank you both for your comments.

    Quote Originally Posted by Antennaman View Post
    Always a good move, along with f connect splitters, wall plates & RG6Q flyleads.
    Yes: the wall outlets now use F type connectors, the splitter already had good connectors. The fly leads aren't anything special: just whatever I had in my junk box. I haven't replaced the cables from the splitter to the wall outlets. I reason that since they're downstream of the amplifier, they aren't so critical, though from reading some of your posts in another thread, I understand that poor quality cable can make them susceptible to interference. One wall outlet is new and has RG6 cable. The others have been added at different times and use different types of cable. We get pretty much the same reception at each outlet, so I've left these cables alone.

    Quote Originally Posted by Antennaman View Post
    What does this TV show on the signal information screen, say for Southern Cross & SBS? (usually under something like Settings/Product Support/System Information/Signal condition)
    I'll take a look when I get home tonight. The Sony TV on the ABC (41) shows Quality = 100 and Signal Strength = 96 to 100. I'll check out the other channels and compare with the Sanyo TV when I get home tonight.

    Antennaman: it sounds like you know the local area pretty well. If you do this stuff for a living and and you're based here, I might have to engage your services if I don't get anywhere with it myself.

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    I certainly dont want to muddy the waters any but although today with mass produced everything, you would think every make and model TV would preform the same but this isnt always the case, at least with quality of picture.
    Back in the days of kerosene powered analog TV's, there were a couple of brands that advertised made for Fringe area reception areas but whether they were that much better is anybodies guess because most only had one TV and reception from house to house in poor reception areas can vary from from just aweful to bloody woeful.
    While I have never met Antennaman and cant and wont vouch for him, he has been a member here for sometime and his advise and suggestions to those needing help has shown he has the knowledge and expertise of his field and after me wasting considerable time and effort trying to attain an elusive signal, one visit by another respected Forum Member had me up in running because he had the right equipment and expertise to use it so I would seriously consider that option.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    Quote Originally Posted by Antennaman View Post
    What does this TV show on the signal information screen, say for Southern Cross & SBS? (usually under something like Settings/Product Support/System Information/Signal condition)
    SCTV: Signal quality 98-100, signal strength 91-04
    SBS: Signal quality 100, signal strength 99

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    Quote Originally Posted by shred View Post
    SCTV: Signal quality 98-100, signal strength 91-04
    SBS: Signal quality 100, signal strength 99
    Unfortunately, that doesn't tell me much.

    The quality readings on these sets are usually after several levels of error correction, therefore, they tend to indicate everything is alright up to the point of failure. Unless this is happening at the instant you have a problem, you may think all is good.

    Similarly, strength readings tend to max out once the upper minimum threshold required for reception is reached.

    I was sorta hoping the Sony may have given ber readings, these can be a little more illuminating.

    Quote Originally Posted by shred View Post
    but also every time an aeroplane goes overhead....about 30km from the Mount Barrow transmitter site
    Lilydale? If not, your location could be helpful.

    Quote Originally Posted by shred View Post
    Antennaman: it sounds like you know the local area pretty well. If you do this stuff for a living and and you're based here, I might have to engage your services if I don't get anywhere with it myself.
    I'm based at Devonport when in Tassie, & travel up to a 50K radius from there, so it's unlikely I would be able to assist.
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    Am located in Trevallyn, Launceston.

    There is more info on the TV System Information page - not sure which bits are useful. Does this help?

    SBS:
    • Pre viterbi: 0
    • Post viterbi:0
    • C/N:34
    • 5s:0
    • UEC: 0
    • AGC:122


    SCTV:
    • Pre viterbi: 4.40 e-5
    • Post viterbi:0
    • C/N:28
    • 5s:0
    • UEC: 0
    • AGC:143

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    The snapshot of those figures is good.

    Usually when things go pear shaped, Pre viterbi is around 1 e-2, and UEC can go positive.

    AGC is a measure of the signal strength, higher reading for higher levels. I can't recall what a usual reading is for this parameter.


    Quote Originally Posted by shred View Post
    Am located in Trevallyn, Launceston.
    Ahh, thought you were more out of town.

    Have you tried Juliana St?

    Still thinking antenna location & type may be the solution for your issue. I do go to Lonny about once a month, I have digs in West Lonny where reception from Barrow is perfect, so I could possibly look at is some time if it comes to that.
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    shred, taking the readings shown on the TV info page can be distorted if you have an MHA in line as the set now reads the input off that and not the true signal at the antenna.
    I am in a declared 'Blackspot' area and the FTA reception literally varies House to House as being a village, the houses are scattered and I know from my FTA reception, the indicators on the TV show either a 100% or nothing depending on the prevailing conditions.
    This false reading was one part of my many problems when I was looking for the best spot to locate the antenna but with the right equipment the knowledge to use it, took barely 15 minutes after me spending quite a few hours spread over several weeks setting up a TV, antenna and generator around my 1/2 block.
    Admittedly I had nothing better to do and it was one of those things you do because you want to but the reality was I was getting nowhere fast.
    With Analog you had a fighting chance without too much expertise and equipment and although the Digital picture is exceptional compared to grainy noisy analog, its a bloody pain for the 'Back Yarder' types like me to instal unless your in an area where there so much signal, your poor instal is acceptable.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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