TDoA Fails

Hi All,

It struck me that it may also be worthwhile listing TDoA fails.

It's not so easy to learn from TDoA's that have worked well, but by examining what hasn't worked, we may get a better idea of what has gone wrong and possible ways to solve it.

I'll start the ball rolling with NVIS propagation.

I've had a couple of days recently where I've been trying to TDoA some UK stations operating around 5MHz. During the mid morning until early afternoon, I'd been getting two strong bands several 100km apart displayed on the TDoa combined map.

I think this is due to multiple NVIS propagation paths obscuring the true location.

When I tried again later in the evening I was able to locate the source.


Martin - G8JNJ


  • edited July 2018
    My professional HF efforts are about 95% NVIS. It is not unusual to have multiple skywave components but also groundwave out 100's of KM. My work involves use of waveforms that accommodate doppler and multipath so operation is still possible but the TDoA scheme has no way to overcome that.
  • Hi John,

    I ran a few TDoA's this evening around 2, 3.8 and 5.2MHz from about 19:00 to 19:40UTC

    Although they passed the new algorithm test I didn't get any results back even when I waited for >5 mins ?

    On another occasion I ran an old algorithm TDoA and got a result back, then tried a resubmit using the same samples with the new algorithm, but didn't get any results back.

    Was the server busy or could it be some other problem ?


    Martin - G8JNJ
Sign In or Register to comment.