Help - Can't Get Channel 7? Everything Else Works Perfect? What Is The Science behind It (Ie Frequencies and Aerial Lengths) ?

tunzafun001 on 13/08/2021 - 14:05
Last edited 13/08/2021 - 18:21
  • Update - now solved

Hi all,

Have a TV in the back shed. Has a roof mounted aerial, an older UHF type, but should still work. The bars run in the appropriate horizontal axis.

The reception for every other channel is perfect, but don't get channel 7 at all (which ironically is the only channel I want for the footy in the shed).

Looking at the frequencies, Channel 7 is the smallest of the frequencies. ie.

7 HD Digital (Seven Network) LCN: 70 Freq: 177.5 mHz
Nine Digital (Nine Network Australia) LCN: 9 Freq: 191.6 mHz

Now I assume the length of the bars on the aerial (and maybe the distance between them) are the key for reception? There must be a formula for this?

Just wondering if I can cut a bar, or even add a shorter or longer bar etc to pick up the 177.5 mHz?

or perhaps is there certain material that 177 mHz can't penetrate, but 191mHz can. Ie house, trees etc in the way?

Seems a waste to replace the entire aerial as the other channels are perfect.

Cheers

Electrical & Electronics

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Comments

  • mskeggs on 13/08/2021 - 14:20

    Where is the signal broadcast from (or, where are you located, broadly) EDIT: Duh, Mildura. It can be the case that one transmitter handles some stations, and one in another direction does others.
    With a good signal on other stations, you might still get them good if the antenna was pointed differently to get 7.

    • mskeggs on 13/08/2021 - 14:22

      oops, not that as it seems there is only a single transmitter for Mildura.

      • tunzafun001 on 13/08/2021 - 14:28

        Yeah, one transmitter. I've downloaded a nice DTV app (that points to direction your aerial should be pointing ). Will try that, but thought the others wouldn't be perfect if this was the case.

        • timthetoolman on 13/08/2021 - 16:11

          They are sometimes out of what. Could try looking at your neighbours and facing it the same way
          Or double check your connections, wiggle them around and see if it's just the crimps

  • Seraphin7 on 13/08/2021 - 14:24

    You sure your TV hasn't just dropped the channels and that the "auto retune" doesn't just fix it up?

    • tunzafun001 on 13/08/2021 - 14:29

      Yeah, tried an auto and manual tune on differing days (to allow for cloud issues etc). Everything but 7 every time !!

  • pharkurnell on 13/08/2021 - 14:29
    +8

    Losing Ch 7 is a loss? You learn something everyday on OzB

    • tunzafun001 on 13/08/2021 - 14:29

      Shed TV = footy = 7

      • pharkurnell on 13/08/2021 - 14:30
        +1

        isnt it 1 game a week? Go Kayo FTW?

  • Typical16-bitEnjoyer on 13/08/2021 - 14:32
    +2

    Get Kayo. It rocks.

  • Platinumtelecom on 13/08/2021 - 14:38

    Depending on where you are located then perhaps you are looking for 7prime?
    I am in Bowral and can only get 7prime. Which is the same thing, just the local version from Wollongong.

  • skid on 13/08/2021 - 14:51

    Have you tried spinning the aerial in every direction?

    Can you pick up Channel 7 from the house?

    You're right houses, trees, mountains etc can get in the way. You could try elevating the antenna higher.

  • orangetrain on 13/08/2021 - 15:04

    Kayo, Murdoch sports! Better than Stokes Ch7 sports. Which billionaire do you want to support, OP?

  • ajm07 on 13/08/2021 - 15:12
    +1

    I'm not an antenna technician. But yes I think the lowest frequency would work best with an antenna with a LONGER main element (not sure how you do that!), and potentially with the other director elements spaced a little further apart than they are now spaced.

    I'm not suggesting you hack your antenna apart.

    • Catullus on 13/08/2021 - 16:51

      Absolutely correct. Smaller frequency, larger wavelength. Spacing between, not worth worrying about.

    • tunzafun001 on 13/08/2021 - 18:14
      +2

      Thanks blokes. The Physics checks out. I now have perfectly clear channel 7.

  • jpl on 13/08/2021 - 15:26
    +2

    If you profile's location is true, Mildura will be receiving TV transmission from Broadcast Australia's site, Calder Hwy 8 km South of Red Cliffs. https://myswitch.digitalready.gov.au on VHF.

    Seven PTV6 177.500 Mhz
    Seven PTV6 177.500 Mhz
    Nine STV7 184.500 Mhz
    SBS SBS8 191.500 Mhz
    Ten MDV10 212.500 Mhz
    Ten MDV10 212.500 Mhz
    ABC ABC11 219.500 Mhz

    All the above channels are from the same location.

    If you have an UHF antenna, it will be hard to get the VHF signal (not totally impossible). Some UHF antennas cover a wider range of frequencies.

    Like you said, 177.5Mhz is the lowest of the range, maybe you should consider a proper VHF antenna?

  • Randxyz123 on 13/08/2021 - 15:48

    Can you get wifi out to the shed and use Kayo?

    Unless you really know what your are doing I’d personally get Jim’s antennas or similar out before you start chopping antenna bars so you don’t start having issues with other channels.

  • sam-1966 on 13/08/2021 - 16:52

    We had a similar problem with 9 at one stage (I didn't much care, no interest in football) - ended up getting an antenna tech in and it was the cable. As soon as it was replaced, 9 worked fine.

  • slow on 13/08/2021 - 16:56

    Maybe check your aerial cable, I was getting similar and went up in the roof and moved the cable away from any downlights and other electrical interferers which resolved it

  • tunzafun001 on 13/08/2021 - 18:19
    +4

    Update - I took the advice above and added a longer bar to the back rod of the aerial. Also used the DTV aerial direction app (which pointed directly at the neighbours extension), pointed the aerial at a gap somewhere in between..and bingo. All channels on the 7 frequency work!

    Next step was clean the aerial connectors and replace cables. But not required yet.

    Thanks again everyone for the help!

  • jug123 on 13/08/2021 - 18:35

    Have you checked the TV somewhere else that you know channel 7 works? Moved house a cpl of yrs ago and lost channel 10. Thought it was an issue with the anntena so got the guy out and he tested said nope all gd so moved the TV to another antenna point and still no channel 10. Borrowed another TV and bang channel 10 was there. Assume a cold soldier joint somewhere. Even though it was a digital tv bought a cheap set top box and it fixed the problem until we upgraded the TV

  • the Unforgiven on 15/08/2021 - 00:02

    Like jpl recommended, go to myswitch. Put your address in and follow to find what sort of aerials work best for your area. You can't just add or subtract unless you know what you are doing because you have to work to a formula, check YouTube out for videos on that. Find out what sort of antenna works best for your area and get one from Jaycar, or:-
    If you have good internet, get an Android Box
    I have this one, you can buy one with or without a mini keyboard, just check all the specs out; or go with another brand - https://www.amazon.com/s?k=pendoo+t95+android+10.0+tv+box&cr…

    • tunzafun001 on 15/08/2021 - 10:47

      Cheers, but all sorted. Ended up copying the length of the longer bars on the working house aerial. Worked a treat.

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