• Relative signal strengths

    From Brian Gaff@21:1/5 to All on Tue Jun 7 09:28:46 2022
    Here line of sight to Crystal Palace, I normally get very good tv reception with a wide band loft aerial. I fear it might well be time, once again to change its coax or get a decent aerial fro Freeview. T multiplex which has channels 20 21 and some others on it is coming up no signal all of a
    sudden, unlike the others. Is this one particularly weak or very high in the band at this site. Its been fine for years, so unless its on reduced power,
    I guess its more expense. sigh.
    Brian

    PS I just tried the discone from my radio scanner on the TV, and get all
    the channels no problems, so I guess that is rather an obvious pointer that
    I have an aerial with built in attenuator all of a sudden. Last time it
    looked like something had eaten the pvc out of the coax. What is the best
    stuff these days? Maybe one that wildlife won't eat?
    grin

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  • From Andy Burns@21:1/5 to Brian Gaff on Tue Jun 7 09:47:55 2022
    Brian Gaff wrote:

    multiplex which has channels 20 21 and some others on it is coming up no signal all of a sudden, unlike the others. Is this one particularly weak or very high in the band at this site.
    Sounds like you mean the SDN/COM4 mux which has LCNs 20 drama and 21 5USA

    That's on UHF E25, i.e. there are other muxes higher and lower frequencies than it

    It's a 200 kW mux like most of the others, except local TV and COM7 which are lower power, but COM7 is going away at the end of the month.

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  • From Woody@21:1/5 to Brian Gaff on Tue Jun 7 13:48:55 2022
    On Tue 07/06/2022 09:28, Brian Gaff wrote:
    Here line of sight to Crystal Palace, I normally get very good tv reception with a wide band loft aerial. I fear it might well be time, once again to change its coax or get a decent aerial fro Freeview. T multiplex which has channels 20 21 and some others on it is coming up no signal all of a
    sudden, unlike the others. Is this one particularly weak or very high in the band at this site. Its been fine for years, so unless its on reduced power, I guess its more expense. sigh.
    Brian

    PS I just tried the discone from my radio scanner on the TV, and get all
    the channels no problems, so I guess that is rather an obvious pointer that
    I have an aerial with built in attenuator all of a sudden. Last time it looked like something had eaten the pvc out of the coax. What is the best stuff these days? Maybe one that wildlife won't eat?
    grin

    If you are L O S to X P it is possible the issue is excess signal, not
    too little, plus - as a radio amateur you should know - we are at the
    time of year when we get many and various lift conditions that can cause
    all manner of problems. I would suggest Toolstation item 86843 which is
    a 0-20dB R F attenuator with F-type connectors.

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  • From Brian Gaff@21:1/5 to Woody on Tue Jun 7 18:32:27 2022
    I'm not convinced its overload or lift conditions this time, It definitely
    says no signal. But I'll test it tonight again. Last time water had got into the coax. No sign of it on the bottom as you can often find if its got in.
    What is the most durable cable these days.
    Brian

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    "Woody" <harrogate3@ntlworld.com> wrote in message news:t7nhfo$2di$1@dont-email.me...
    On Tue 07/06/2022 09:28, Brian Gaff wrote:
    Here line of sight to Crystal Palace, I normally get very good tv
    reception
    with a wide band loft aerial. I fear it might well be time, once again to
    change its coax or get a decent aerial fro Freeview. T multiplex which
    has
    channels 20 21 and some others on it is coming up no signal all of a
    sudden, unlike the others. Is this one particularly weak or very high in
    the
    band at this site. Its been fine for years, so unless its on reduced
    power,
    I guess its more expense. sigh.
    Brian

    PS I just tried the discone from my radio scanner on the TV, and get all
    the channels no problems, so I guess that is rather an obvious pointer
    that
    I have an aerial with built in attenuator all of a sudden. Last time it
    looked like something had eaten the pvc out of the coax. What is the best
    stuff these days? Maybe one that wildlife won't eat?
    grin

    If you are L O S to X P it is possible the issue is excess signal, not too little, plus - as a radio amateur you should know - we are at the time of year when we get many and various lift conditions that can cause all
    manner of problems. I would suggest Toolstation item 86843 which is a
    0-20dB R F attenuator with F-type connectors.

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  • From Mark Carver@21:1/5 to Brian Gaff on Tue Jun 7 19:13:47 2022
    On 07/06/2022 18:32, Brian Gaff wrote:
    I'm not convinced its overload or lift conditions this time, It definitely says no signal.
    But how does it determine there's a signal ?  Usually for digital
    receivers if they can 'see' a valid COFDM signal.

    Point a DVB-T only receiver at a DVB-T2 mux, and it will also say 'no
    signal'

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  • From Brian Gaff@21:1/5 to Mark Carver on Wed Jun 8 06:01:52 2022
    Well its working again last night. I wonder if it was on low power for some reason the day before? I'm still very suspicious that its not working well, since the discone experiment. I mean its not even tuned to the band, its broadband by its nature, and not very polarised either.
    Brian

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    "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:jg9iqsFpnq7U1@mid.individual.net...
    On 07/06/2022 18:32, Brian Gaff wrote:
    I'm not convinced its overload or lift conditions this time, It
    definitely
    says no signal.
    But how does it determine there's a signal ? Usually for digital receivers
    if they can 'see' a valid COFDM signal.

    Point a DVB-T only receiver at a DVB-T2 mux, and it will also say 'no
    signal'

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