Radio China International Echo Mystery SOLVED!

For the past month or so I have been wondering about a strange echo that I've been hearing on the 31 meter transmissions of Radio China International.  I first noticed it on my "Kings Speech" regen receiver.  Then I heard it again on my "Off the Shelf" regen.  

For a while I thought that what I was hearing was a propagation effect:  Perhaps the very strong RCI relay station in Quivican,Cuba was sending north a signal so strong that it was travelling around the earth along the grey line and coming back to me about .133 seconds after the original reception.  

This sounded plausible (and it does happen sometimes).  But there were reasons for skepticism: Why wasn't anyone else hearing this?  Why wasn't the effect showing up on signals from Radio Havana Cuba?  

Pete Juliano had suggested that perhaps I was getting signals from TWO different RCI transmitters.  I had quickly checked the RCI schedule and didn't see them transmitting on the same frequency at the same time from multiple transmitters, so I kind of put that idea aside.  Hey, the round-the-world idea was just more appealing! 

But then I remembered something strange about the echo:  It seemed to disappear when I tuned close to the center frequency of the RCI signal, but then appeared when I tuned off to one side. Hmm.... That was an important clue. 

I've long been wary of regen receivers and for a while suspected that I was dealing with some weird regen effect.  Regen and Echo seem to go together, right?    Well, as it turns out, no.  But I was right about this being an effect of the nature of my receiver... 

Last night I was listening to RCI English service at around 0030 UTC on 9570 kHz.  Nice clear signal.  No echo. 

At 0100 UTC the program changed, and the echo started.  A very strong echo. 

I went to the RCI schedule.  Here I found the answer: 

At 0030 they were transmitting from their relay station in Cerrik, Albania on 9570 kHz. 
At 0010 they switched programs, frequencies and transmitters.  At 0100 Cerrik shut down, but the Quivican, Cuba relay came on on 9580 kHz.   At the same time the RCI transmitter in Kasi Sabagh in far-off exotic Western China, in Xinjiang, fired up on 9535 kHz.  Both transmitters were carrying the RCI English service. 

You see, my little regens are not very selective, and the RCI transmissions are quite strong.  So if I have my receiver tuned to around 9560 kHz, I'll be hearing BOTH the signal from Cuba AND the signal from Xinjiang.  That would explain the echo. 

To try to confirm this, last night I fired up my old Hammarlund HQ-100 receiver to see if I could discern the two different signals.  I could.  And the echo appeared when I tuned BETWEEN the two.  You can hear this in the video above. 

There is one remaining question here:  Is the echo caused by the RADIO path difference between the two transmitters?   Or are we just seeing the effect of the programming being transmitted at slightly different times, perhaps with this delay caused by INTERNET latency?  Anyone know how RCI gets its signals from its Beijing studio to its distant transmitters?   I calculate that the path difference is about 10,000 km.  With c at 300,000 km/second, that would yield an echo of only about .03 seconds.  The echo we are hearing sounds longer than that, so I suspect we are hearing a difference in studio-transmitter transmission time.  What say the SWL RF gurus?

BTW:  I think the same phenomenon may explain the echo on Brother Stair's "Overcomer" signal.  I see that starting at 2200 UTC he is on BOTH 7570 kHz and 7730 kHz from RMI transmitters in Florida.  Perhaps they are not synched up. 

I think this is all very cool.  Think about it:   Here I am, sitting in Virginia in 2014, listening to the Albanian, Cuban, and Xinjiang relay stations of Radio China International on a receiver first built by some guy in England during the 1930s.  And I'm trying to figure out if the echo I hear is caused by the limits imposed by the speed of light and the size of the earth,  or by the time it takes packets to move through sub-oceanic fiber optic cables.   

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Making Hardware for Mars in a Lab in New York City

I liked this video about building hardware for a Mars mission at a lab in New York City.

http://www.sciencefriday.com/video/08/10/2012/building-for-mars-sometimes-painful-always-glorious.html


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The Amazing Apollo Board from Carbon Origins

Wow, lots of possibilities here....

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Arduino Makes Music with Old Floppy Drives

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A Beautiful BITX20 from PA1ED

Edwin did a beautiful job on his BITX.  This is an excellent example of stage-by-stage construction. 
This is his THIRD BITX.  On the second one he got all the parts from an old television and a washing machine.  That's the true BITX spirit!  
I want an S Meter!  
There is more information on his blog:
http://pa1ed.blogspot.nl/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

The SWLing Post, Ears To Our World, and the HumanaLight

Thomas, K4SWL, has a really impressive shortwave listening blog.  Yesterday he was kind enough to post an article about my latest obsession:  the echoes on China Radio International: 
http://swling.com/blog/ 

Even more impressive is Thomas's work on behalf of poor people in the Third World. He is the Director of Ears to Our World, a charity group that provides innovative, simple and appropriate technologies to schools and communities in remote, rural and impoverished regions of our world.
Here they are: http://www.earstoourworld.org/

They distribute radios to people who would no other regular technological contact with the rest of the world.  They are also involved in an intriguing project called the HumanaLight:  "Dead" AA batteries power lights that can make a big difference for people living in areas that have never been on any grid.   Here it is: http://www.earstoourworld.org/humanalight/

Ears to Our World is looking for Donations to help them bring light and radios to people who really need them:   Here is where you can help: 
http://www.earstoourworld.org/donate

This is clearly a very appropriate charity for radio amateurs. 

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Inducted Into Shortwave Rogues' Gallery

Jeff Murray, K1NSS, has done me the honor of placing me in his VERY ELITE Friends of Shortwave "Rogue's Gallery."  Check it out:   http://dashtoons.com/FOSW.html

Kind of ironic that I should be recognized for my work on regens! 

Thanks Jeff! 

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"First Smoke" from Antananarivo, Madagascar

Here in Northern Virginia, it is not all that unusual to run into friends and have them say things like, "We're moving to Antananarivo."  Here is a report from Jack, AI4SV on his new location. That garage seems to have real potential as a workshop Jack.   

Greetings from Antananarivo, Madagascar!

I thought I'd turn the tables and give you a bit of travelogue and radio news.

The only radio-related item in our air freight was my toolbox, which I thought was justified. I lugged along the rest of the station in my carry on, an FT817 (with post-market Collins mechanical filter), magnetic palm paddles, a winkeyer, and the 40/20/10 end-fed LNR halfwave dipole, plus some mason line. I also brought a very compact 240V recharger that I had picked up in Sweden. 

The day after I got here, the dipole was hung using the time respected coke bottle on a string method, which greatly entertained the guard assigned to the house. A couple days later, I clambered up on the roof to raise the feed end another ten feet. Since then, I've worked about 240 stations with my QRP rig (all but three CW). I don't have any way to upload to LOTW right now, but my rough estimate is that I have worked something like 45 DXCC entities.

The location is probably not as ideal as Azores in terms of having a nearby salt water ground plane, as we're 100 miles to either east or west coast, and the local noise here can be very high in our tightly packed appliance-heavy diplomatic neighborhood. On the other hand, we're on the central highlands, almost a mile up and Madagascar is a very desirable DX location. When propagation smiles on me, I can work runs of 30+ stations before I disappear again into the ionospheric mist.

Before I got here, I talked with a bunch of US, UK, and German hams who had held 5R callsigns, and they gave me the lay of the land. Phil, G3SWH became my QSL manager and put me in touch with Albert, 5R8GZ, who has been a huge help. Prior to arrival, Albert was able to put through my paperwork with OMERT, the local equivalent of the FCC, so I could get on the air as soon as I arrived. He has similarly assisted quite a number of visiting hams and dxpeditions and is a big proponent of ham radio in scouting here. 

There's no ham club here, but there are so few active hams that in my three weeks here, I've either met or been introduced by email to about half of them.

It will be another month before our main shipment hits the docks here, and meanwhile management has given me the thumbs up to install a tower in the backyard to support a hexbeam. Between the K3 and the hexbeam, I think I'll be in good shape to do some serious operating, although I think that a couple months of operating QRP has been not only a character-building experience, but has given me a much better understanding of propagation patterns.

We have a large, empty garage and I think it's destined to become the workshop. I am curious about how dry it will stay in the rainy season and how many mosquitos will visit me there, but it has electrical power and plenty of wall space for shelving. Packing out my workshop took me about as much time as the rest of the house combined. So many little parts...

My toolbox arrived last week and the soldering iron was put to immediate use to build a dipole for six and then 15 meters. I've captured the moment of "first smoke" in the new location for your viewing pleasure.

So, please look for me on the air in future months and point your moxon over here when you can.  I'm putting updates about the station's status on its qrz page.

Keep up the podcasts! I've enjoyed the series with Pete Juliano - kind of a return to the original format. Also, I've listened to the icq podcast for years, so it was great to hear the "very special crossover episode" with you and Martin.

73,

Jack

5R8SV / AI4SV

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Kiwi Lunchbox Sideband: The Tucker Tin Two

Pete Eaton sent us links to an old article from the New Zealand magazine "Break-In."   So many good, simple rigs come to us from New Zealand!  Who can forget ZL2BMI's DSB rig?  This one is the work of Fred Johnson ZL2AMJ.  It is especially interesting and is in some ways similar to Peter Parker's "Knobless Wonder."

It uses the phasing method of sideband generation.  No crystal filters in this one.  You need TWO balanced modulators.  You have a 90 degree phase shift network for the RF (from the carrier oscillator) and a second 90 degree phase shift network for the AF from the mic amplifier.  When you combine the signals from the two balanced modulators -- viola! -- one of the sidebands disappears.  The balanced modulators take care of the carrier, and an SSB signal is launched.  That is how my old HT-37 works, and similar ideas seem to be at work in modern SDR rigs.  

G3TXQ has the complete set of Break-In articles (it includes a VFO): 
http://www.karinya.net/g3txq/temp/tucker_tin/   

Here is a Canadian article on the rig.   A "Tucker Tin" is apparently what the Kiwis call a lunch boxes (shades of Benton Harbor...).  

Thanks Pete!

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Long Delayed Echo on Radio China International

Several people have e-mailed me suggesting that the weird echo I have been hearing on shortwave broadcast stations is in fact one of the fabled "Long Delayed Echoes" that radio amateurs have been hearing intermittently since about 1927.   I was skeptical at first, but -- at least in the case of the Radio China signal -- I think LDE caused by the signal going around the globe several times does explain what I've heard.  Each trip would add a delay of about .133 seconds, and that seems to match what we hear in my recording:  

http://soldersmoke.blogspot.com/2014/08/strange-echo-on-china-radio.html 

Compare that with what K9FIK recorded on 10 meter SSB (thanks Stephen!): 

http://swling.com/blog/2013/10/hearing-the-speed-of-light-dx-double-echo/
(you can listen to the audio on this one). 

It sounds very similar. 

If this is in fact LDE, I'm lucky -- this is pretty rare.   And it is a eerie that I first heard it on on Regen receiver from the 1920s!  Above is a picture of the regen used to study the FIRST LDEs. See: http://folk.uio.no/sverre/LDE/


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SSB with Just Two Tubes

Here is the two tube SSB transmitter that Pete was telling me about.  This would be a nice companion to the "Mate for the Mighty Midget" receiver that I built a long time ago.  Another Benton Harbor Lunchbox may have to be sacrificed... 


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Eclectic Electronics: Powering Arduinos with Tube Filament Voltage

You know that you are dealing with a broad range of technology when you find yourself discussing how to power an Arduino microcontroller from the 12V AC voltage on a vacuum tube filament line. Thanks Pete. 

Hi Bill,

There is only so much that can be said in 1 hour and 19 minutes so maybe here is some stuff for the blog.

The 1st thing on the list when working with the Arduino when it is not connected to the computer is to have a proper power supply. My research as indicated that 9 VDC “raw” is a good starting point to power the Arduino boards so here are two supplies that will provide that power.

I did find that it was necessary to have an isolated supply when working with the “toob” radios and even to isolate the RF into the radio using a ferrite core transformer –some more tribal knowledge.

One supply takes an 8 VDC regulator and boosts its output to 9 VDC. The second uses a switching regulator and the beauty of the second is that the input can be either 12 V AC or DC. This is ideal for use in toob radios where you can sample the 12.6 VAC filament string.

73’s

Pete

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