Sunday, May 28, 2023

Long-delayed echo recorded during CQ-WPX-CW?

Jon EA2SN, operating as EE2A during this weekend's CW contest, recorded a segment of his own transmission soon after going back to receive.

Jon was using an Elecraft K3 at 100 watts on 20m with a vertical antenna. The recording was made on 27 May at 0713Z.

The delay was 1.272 seconds.

(UPDATE: As Sverre mentions in the comments, it is meaningless to attribute this degree of accuracy to a transceiver - after all, it is not a piece of test equipment. So let's assume a 1.2 second delay).

This delay is too long to be explained by normal long-path propagation of his own signal back to him - over 10x too long.

Jon shared an MP3 file of one of the examples. I opened the file in Audacity so that it could be seen visually and so that cursors could be placed in order to measure the exact delay:

Sverre LA3ZA explains part of the delay here.

But still - almost 1.3 seconds is a very long delay, even when factoring in sidetone/RF transmission timing differences + receive processing time + LP propagation. The sum total should amount to far less than 150mS.....




  1. This is cool! When estimating delays like these, one should be aware that ham radio transceivers are not precision instruments, and in particular that there are unknown delays between transmission and sidetone, as well as an unknown processing delay in the receive chain. This is especially true in modern digital transceivers. Here are some examples from the Elecraft K2 and K3:

    LA3ZA, Sverre

    1. Ok that may explain it then, Sverre. So it could be LP propagation with the extra delay being attributed to differences between sidetone and actual transmission of what the sidetone represents. A new transmitter spec that would be interesting to know...

      Thanks much! 73,

    2. No, there is no doubt that it is a long delay, longer than 1 second. But it cannot be measured to the nearest ms or 10's of ms unless one knows the internal delays of the transceiver. In my examples, the K3 has an error of about 50 ms, dependent on settings. The analog K2 only 12 ms.

    3. I understand, Sverre - no need for me to have gone to the 2nd or 3rd digit to the right of the decimal point...

      I know you've written a lot about LDE's on your blog in the past - what is your opinion of what may be happening here?

    4. Out of the five mechanisms alluded to here in the link belw (follow links from there), I think the most probable one is 3. Mode conversion involving coupling to mechanical waves in the ionosphere, but it is hard to come up with a test for verifying that.

  2. Possible mechanisms for LDE are here incl a presentation from HamSci '21:

    My guess would be Mode conversion involving coupling to mechanical waves in the ionosphere, i.e. #3 here:

  3. From Jon EA2SN:

    No, the delay was only on this QSO and there was no trace of echo on
    the remainder of the recording (as it can be seen in the traces using

    I was using the K3 locally and QSOrder with N1MM.

    Maybe it was an artifact of the recording, as 1.3 s delay does not fit
    on any known mechanism. Or it was the devil... for DD1D was sending as the exchange "666" :-) :-)

    Be well,
    jon, ea2sn / ee2a / ae2sn

  4. When I was a new ham I experienced an LDE. I was calling CQ on 15 meters I think and when I switched back to receiving I heard "de wb2ems wb2ems k" in *my* fist. T60/HQ170 so no fancy digital delays. I'd seen a write up in one of the magazines so I had heard of it but never expected to hear one. Very odd.