28 February, 2013

Long Delayed Echo on VOA Chinese Service

Thierry, F4EOB from Paris is still hearing strange echoes on the VOA Chinese service broadcasts. There isn't really any good explanation for this phenomenon.

Now during winter he is hearing it both on 13650 kHz from 9 to 12 UTC and on 21590 kHz from 9 to 11 UTC. The 21590 kHz transmission has been heard by him for a long time and I mentioned it here last year also. As then the echo is about 2 seconds. Thierry also made a youtube video of it with a recording.

The transmitter locations are in Asia. The 19 m band site is on the Mariana Island (Tinian) and the 13 m band transmitter is in Tinang in the Philipines.

In my blog last year I discussed possible explanations such as multiple transmitters or multiple round-the-world travel. But since the delay is so consistent and has had the same delay for such a long time, the probability that it is man-made is rather large.

Thierry tells me that this LDE can easily be heard with the WebSDR at the University of Twente in the Netherlands also. I would be curious to hear from people outside Europe who could compare the Dutch WebSDR with their own local reception and see if the same echoes are heard everywhere.

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2 comments:

  1. Anonymous09 August, 2013 13:17

    Maybe they use severler transmitter located far away and use satellite link for the audio feed, hench the delay.

    73 Jan LA3EQ

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  2. Sverre Holm09 August, 2013 13:37

    Hi Jan

    Thanks for the comment and sugestion. Yes, the satellite delay could be one explanation. It isn't so large though, only in the order of 1/4 second round-trip. Also, I find it hard to believe that they don't compensate for such delays. With today's digitally processed signals that would be a trivial thing to do.

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