Radio navigation: RDF and ADF

Discussion in 'Aviation' started by Jenisch, Jun 7, 2015.

  1. Jenisch

    Jenisch Active Member

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    Hello,

    Please, someone can explain to me what is the difference between the RDF radio navigation system used in WWII planes and the (post war?) ADF system?
     
  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    They are technically the same except there are/ were specific stations to provide ADF navigation and later NDB instrument approaches.
     
  3. stona

    stona Well-Known Member

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    Doesn't ADF display a bearing to the beacon continuously and automatically whereas in older RDF systems a bearing to the beacon had to be found and calculated by the navigator? I've read that this led to more than one instance of a crew using the system flying on a reciprocal bearing and delivering their aircraft into enemy hands as a result.
    Cheers
    Steve
     
  4. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Both just point to the radio source. The ADF traditionally has a rotating "card" or dial face that can be used to calculate bearing and course.

    Non-directional beacon - Wikipedia, the free encyclopedia
     
  5. Token

    Token Active Member

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    Are you asking about the operational differences? Or are you asking about the technical differences?

    The two systems perform the same basic task.

    A loop antenna is turned (either electrically or mechanically) to find the null to a known radio transmission, that is, tuned until the signal is weakest. The null (weakest signal) is used instead of the peak (strongest signal) because loop antennas have very broad peaks and very narrow nulls, meaning the null results in a more accurate and definable measurement. Loops actually have two nulls and two peaks, each 180 degrees apart. That means there are two possible nulls, one of them pointing towards the source signal, and one pointing 180 degrees away. To remove this uncertainty factor a “sense” antenna is added to the loop antenna, resulting in only one null, still with two peaks.

    Both systems work by tuning to a desired/known radio source, the differences occur after the frequency of the radio source is tuned. In the earlier RDF systems an operator turned the antenna, observed the null in signal strength, and plotted / used the direction indicated. In the latter ADF system the null was automatically tracked and the results repeated on an indicator.

    T!
     
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