Strange Echo on China Radio International

Last night I was doing some shortwave listening on my new (OLD!) regen.   As always, China Radio International was booming in on multiple frequencies. But as I tuned them in, I noted something strange:  a very distinct echo on the signal (you can hear it in the video above).  Very strange.  Kind of like the Long Delayed Echos we've all heard about.  I started thinking of explanations.  Might this be some weird regen reverb effect?   (You see -- I'm still wary of these regens!)  But no, I checked -- the echo was there when I listened with my superhet HQ-100.  Could it be that this was some strange multipath effect, perhaps involving multiple powerful transmitters in different locations?   I was listening to the 0100-0200 UTC (20 Aug 2014) CRI English language service. (The echo continued when they switched to Chinese at 0200)  I think the frequency was 9580 kHz.   An SWL website says the transmitter was a relay station in Quivican, Cuba.

What do you guys think?  These fellows might have an explanation: 
http://swling.com/blog/2014/07/china-radio-international-warbling-on-daves-home-brew-receiver/

I really like shortwave listening with this old homebrew 1930s radio.  There are still a lot of interesting signals out there.  Recently heard:  Voice of Vietnam,  Radio Turkey, Radio Romania, WWV, WWVH, CHU, W1AW,  transatlantic aircraft,  Radio Australia, Radio New Zealand... and the mysterious numbers. 

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