Does frequency have an impact on distance?

Discussion in 'General Electronics Chat' started by electronewb, Apr 8, 2013.

  1. electronewb

    Thread Starter Member

    Apr 24, 2012
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    3
    Does a frequency have an impact on transmission distance? For instance would 2GHz would have the same throw has a 7GHz microwave transmitter? Or this just comes down to the amplification of the signal. And what are the advantages to have different frequency range?

    For example this unit can do 2GHz and 7GHz digital transmission

    http://broadcast.vislink.com/products/products/?Category=3&Product=36
     
  2. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    Generally speaking,attenuation increases with frequency.

    The OB links I used to look after from time to time had one link on 7GHz,& the other on 14GHz.
    Over normal paths,the difference was minimal.

    At one Transmitter site,the Studio/Transmitter links (STL) was on around 2.5 GHz,& at another they were around 8GHz--similar distance,similar results.
    At extreme distances,such as Amateur Radio Operators deal with,the differences in attenuation become important,but for commercial links,it is not a major problem.

    Different bands?

    If you have a double hop link,if both hops are in the same band,there is the danger of interference at the terminal receiver,due to such things as Tropospheric Ducting,where the signal from the first hop appears at similar strength to that of the second hop,causing interference.

    When exactly the same frequencies are re-used,as in long distance microwave systems,they are usually sufficiently separated geographically to stop this occurring.

    That said,the East/West microwave system running roughly parallel with the Great Australian Bight,was affected by Tropospheric Ducting
    during part of each Summer.

    Hams commonly communicate between southern WA & South Australia using Tropospheric Ducting during this part of the year.
     
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  3. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    So would the 2hGHz have the exact same quality as the 7GHz digital transmitter. What make a frequency more favarable than another one?
     
  4. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    I think in a lot of cases,it is whatever frequency the Licencing Authority lets you have.

    As I said above,you can pretty much ignore the difference in practical use.

    Of course,in the circumstances I described where you have a double hop link,the two widely separated frequencies are a good idea.

    With digital rather than analog links,there may be more margin for error.
     
  5. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    Thanks for the reply. By double hop links you mean 2 separate receivers? Do some frequencies in digital transmission carry a signal better than other frequencies like in analog?
     
  6. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    No,a "double hop" is where the link is in two sections.

    For instance,there may be a link from the OB site to a large hill,then another link relaying the program material from that hill to the studio.

    If both sections are in the same band,there is the chance of the signal from the first link interfering with that of the second link.

    Digital modulation is more rugged in terms of possible problems,but things can still happen.

    As I said before,in normal use,the differences between different frequencies can usually be ignored.
     
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