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Thread: Upgrading an Old TV antenna system to a New one

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    Default Upgrading an Old TV antenna system to a New one

    Why did this...


    Last edited by ol' boy; 26-05-20 at 09:02 PM.
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    Work better than this?

    Last edited by ol' boy; 26-05-20 at 09:03 PM.
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    Theory would dictate the F type should work better... but it has double the loss being 8-way versus 4-way.

    Do you have signal readings (signal strength and BER/MER) before and after?

    The cable needs to be replaced as well, as its likely corroded further along.

    If its air-spaced coax, it likely has water right through it.

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    Thanks mtv, i only truly learned the losses in an 8-way from reading last night
    I was really surprised to find out that 4-way, 6-way and 8-way are just cascades of 2-way splitters...
    I really thought they would be a point source connection inside, not staged like they are.

    Job is a mix of 32 year old RJ59 and some RG6 Quad
    The trunking cable is now RG6 and a couple of outlets are RG6

    Point is, it worked prior with the old horrible corroded splitter with saddle and screw terminations
    I guess it must be the 8-way losses at play

    Sadly, i don't have a meter and cant provide readings, which is really where this all needs to start
    The system is pointed at Mt Dandenong (200km away) but also gets side injected from a local UHF translator with regional broadcast.

    The system started life as a 4 outlet, but has grown to 7 outlets over time.

    It is 7HD and SBS Viceland HD from Mt Dandy that break up first (weather dependant)
    Last edited by ol' boy; 27-05-20 at 05:50 AM.
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    What do you mean by 'side injected'?

    Are there any amps in the circuit?

    Too much signal (including out of band signals) can cause bit errors and reception loss, which can be mistaken for poor signal, as the outcome is identical.

    It's possible the 8-way may actually be improving the signal too much... even with the insertion loss, especially if you have any amps.

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    2 Separate Antennas

    1 x Wide Band VHF and a UHF, combined in a Kingray Masthead Amp
    Pointed at Mt Dandenong (200km away)

    The "side injection" is what it picks up from the Local UHF Band 5 Translator, even though it not pointing at it.


    Antenna
    (Top 2, the other is FM and seperate)




    Old School Kingray Masthead Amp power supply
    I just noticed the shielding touching the 300ohm inputs.



    This is the local translator
    .
    (All these channels work great, even though there is no Band 5 antenna, nor anything pointing at the local tower)



    Melbourne channels the system is pointing too




    Gets C31 great and its the weakest of them all
    Last edited by ol' boy; 26-05-20 at 11:24 PM.
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    Wideband VHF will be prone to picking up out of band signals.. eg: strong local FM.

    For Melbourne, you only need an antenna for channels 6-12.

    A band 5 UHF antenna should be pointed at your local translator.

    The UHF signals will need little amplification, if any.

    Bandpass filters for the channel groups will drastically reduce unwanted signals.. FM, paging, cellular, 2-way, etc.

    The amp needs to only amplify the required bands, with adjustable level controls to balance output levels.

    It's impossible to know what is exactly happening without test measurements, but you're doing well to receive Melbourne at 200 k's away.

    EDIT: Just saw the pics you've added. The VHF antenna will favour low band signals... which don't exist for TV now, but it will pick up interfering signals, causing tuner overload.

    You definitely need a new masthead amp.... of the type I described above.

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    Quote Originally Posted by mtv View Post

    It's impossible to know what is exactly happening without test measurements, but you're doing well to receive Melbourne at 200 k's away.
    The whole town does and always has
    But many had to use a 40ft mast and Masthead Amp

    I think when the local Translators came in, they dropped the power of Mt Dandy...
    But you still receive it, its mostly across the water, so no obstruction....

    Hmmm now i say that, the gumtrees have grown a lot in 30 years
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    Mt Dandenong TX power hasn't dropped.

    C31 is UHF so both the TX and receive antennas have more gain (increasing effective radiated power) and it uses the full channel bandwidth for a single channel... not multiplexed to include multiple channels in the same bandwidth like all the other networks, which is why it performs well.

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    Quote Originally Posted by mtv View Post
    Wideband VHF will be prone to picking up out of band signals.. eg: strong local FM.

    For Melbourne, you only need an antenna for channels 6-12.

    A band 5 UHF antenna should be pointed at your local translator.

    The UHF signals will need little amplification, if any.

    Bandpass filters for the channel groups will drastically reduce unwanted signals.. FM, paging, cellular, 2-way, etc.

    The amp needs to only amplify the required bands, with adjustable level controls to balance output levels.

    It's impossible to know what is exactly happening without test measurements, but you're doing well to receive Melbourne at 200 k's away.

    EDIT: Just saw the pics you've added. The VHF antenna will favour low band signals... which don't exist for TV now, but it will pick up interfering signals, causing tuner overload.

    You definitely need a new masthead amp.... of the type I described above.
    Yes, i am totally amazed a 32 year old system still works today, given all the changes in that time
    Analogue to Digital
    Corroded terminals
    Aging Antenna and designed for the older freqs used in the day
    Introduction of 4G

    Yes, the last local TV Tech started fitting filters and traps to very band specific antenna before the Amplifier (If you wanted Melbourne)
    Or he ripped everything down and fitted a tiny Band 5 UHF pointed the new local translator
    Last edited by ol' boy; 26-05-20 at 11:41 PM.
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    Quote Originally Posted by mtv View Post

    C31 is UHF so both the TX and receive antennas have more gain (increasing effective radiated power) and it uses the full channel bandwidth for a single channel... not multiplexed to include multiple channels in the same bandwidth like all the other networks, which is why it performs well.
    well, you learn something every day, thanks mtv, i hadn't even considered that
    So many changes its hard keep up, especially when its not your game.
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    Quote Originally Posted by mtv View Post
    Theory would dictate the F type should work better... but it has double the loss being 8-way versus 4-way..
    That raises an interesting point, the old design 4-way had a couple of outlets doubled up under the 1 screw.
    Worked better than doing it properly with an outlet per port.

    Why is this?
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    Quote Originally Posted by ol' boy View Post
    That raises an interesting point, the old design 4-way had a couple of outlets doubled up under the 1 screw.
    Worked better than doing it properly with an outlet per port.

    Why is this?
    Again, it's possible the losses may have been beneficial when they theoretically should be detrimental. (Theory and practice sometimes don't match)

    There's lots of weird possibilities, but as mentioned, it's impossible to provide factual answers without accurate signal measurements to 'see' exactly what's happening.

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    yes it would tell the story if you had some meter readings ....

    is it also possible there may be a possibility of a too strong signal due to the amp ..... resulting in a problem with some channels .... (although it is usually thought to be a problem with a too low signal)
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    Wave length equals 300 over frequency in megahertz !!!!! with the photo there obviously not a adherence to the principle , as I can see a lot of parasitic elements coming into effect here ! ok so to look at a practical area every yagi should be at a min of quarter-wave of the lowest freq from any other antenna I also notice that the yagis are past the front of the dishes this is a no-no as the elements radiate into the dish and cause a wide band signal to the receiver and degrade it as its trying to amplify out of band signals instead of the freqs you want amplified if you want to get decent in band signals then you should start with the lowest freq yagis on the bottom and go up with the correct spacing ! spacing of dishes is another thing again as you have to dissolve the side lobes and is best done using practical means .IE put up one dish to start with then add another so that there is no degrading of signal and so on , the main reason is that the oscillators in the lnbs are a cause of interference to the next dish and radiate into each other And get into the yagis as well I would suggest you have a redesign of your system and then apply only the required amplifiers not just amplify every thing with out reason or guess as you add amps you add more interference to the system so all you are doing is amplifing out of band noises and not making head way , hence replacing to old 4 way with a 8 way and finding the efficiency of the new has seem to be worse but in actual fact all its done is improved the system to one area and thus bought out faults in the design good luck Don

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    Quote Originally Posted by mtv View Post
    Mt Dandenong TX power hasn't dropped.

    C31 is UHF so both the TX and receive antennas have more gain (increasing effective radiated power) and it uses the full channel bandwidth for a single channel... not multiplexed to include multiple channels in the same bandwidth like all the other networks, which is why it performs well.
    Does that have any effect at all on MER levels? My impression was that COFDM allow a certain rate of data to be transmitted, e.g more or less channels. But in no way I thought that data rate have an effect on MER levels, as all 64 quadrants are still being used regardless

    Here in Perth i have noticed our community TV (CH32), which is also a single channel on that frequency, performs extremely well under even the most terrible conditions and weakest signal level.
    On new installs, it's always common to see MER levels always are 36db. I had thought good quality newer modulators were used at the transmission site since our Community TV was the latest to come on air, but I always had wondered why it performs very well.
    Last edited by Z2TT; 29-11-20 at 04:28 AM.

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    Quote Originally Posted by Z2TT View Post
    Does that have any effect at all on MER levels?
    Yes, it does, as it uses the full bandwidth of the channel.

    It may also be encoded differently to the VHF channels.

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    Quote Originally Posted by Z2TT View Post
    I always had wondered why it performs very well.
    The licence provisions only allowed for QPSK modulation, which is far more robust than the 64 QAM used by other TV network operators.

    This gives a better coverage area for less power as there are less chances for decoder errors to occur.

    As I understand it, MER is a grab bag of impairments in the reception path (assuming the transmitter is operating correctly) calculated during the decoding of the digital signal. QPSK has far less decision points for the decoder to consider when compared with 64QAM, so can usually give a better reading as the signal degrades to the failure point. UHF transmission also helps, as the signal is generally less subject to atmospheric & man-made noise.

    I didn't think community TV in Perth was still on air, if it is, you can look at the constellation on your meter to see the difference when compared to normal TV transmissions.
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