Chitika: propagation

Showing posts with label propagation. Show all posts

SolderSmoke Podcast #174 is available:

http://soldersmoke.com/soldersmoke174.mp3

March 28, 2015

Happy Arduino Day!
Pete's Belthorn III Transceiver (with cool color display)
Bill's BITX 20 (that used to be a BITX20/40)
AD9850 DDS added to Barebones Superhet
Jean Shepherd on Parasitic Oscillations, Obsession, and Madness
Simple Test Gear for the Homebrewer
Digital Oscilloscopes and their amazing capabilities
Dongles and other great stuff in SPRAT 162
The BIG St. Patrick's Day Solar Flare
VK6MV's Amazing Rhombic (+)
VK7XX (Dos Equis!)
A Bit of BITX History
Pete going KX3 QRO

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

There I was. 0900 UTC (0 Dark Thirty local), the morning after the big March 17 St. Patrick's Day Coronal Mass Ejection Impact. Solar Flux Index: 116. A Index: 117! I'd never seen the A Index that high. When I got home from work on March 17, I had turned on the BITX 20 and heard nothing but white noise. No signals. Nada. Zilch. So the following morning my expectations for 20 were quite low. I tuned across the whole band, again hearing nothing. But wait... there was one signal. And he was calling CQ. With an Australian accent. VK6MV! The only signal on the band. I called him with my recently fixed BITX20 (with .12 kW amp) and a dipole. No problem. We had a nice contact.
A look at Roy's QRZ page shows that he is a fellow homebrewer. Clearly, the radio gods were making a statement here.

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

CONUS HF BAND CONDX

1/22/15 --- 10:45:00 GMT --- REPORT # 1289

160

I think this is a really interesting and useful way to gather and present information on propagation conditions. Check it out. The "instructions" page gives some background info on the technique used.

http://www.bandconditions.com/

The author, Biz, K5BIZ seems like a very FB ham: http://www.qrz.com/db/K5BIZ

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.

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

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/

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

SolderSmoke Podcast #165 is available:

http://soldersmoke.com/soldersmoke165.mp3

September 13, 2014

Workbench Update: Bill's "Off the Shelf" Regen, Pete's Boatanchors
Mysterious Echos on Shortwave Signals. Solve the Mystery. Please.
Microcontrollers -- What they can do for you.
Small world: As a kid, Pete was neighbor of "Digital Dial" N3ZI
NEWS FLASH: Arduino creator Massimo Banzi was a ham!
Born in a bar, cheaper than pizza: The Italian origins of Arduino
Arduino CW generators
No coding skills needed
Arduino + AD9850 = Signal Generator or VFO
Arduinos in the Minma
What the heck is a Shield?
SolderSmoke Mailbag

A few weeks ago I noticed a strange echo on Radio China International's signal. If you scroll down a bit you can see my YouTube recording of the problem. On one of the SWL lists, there was speculation that this problem was the result of a flaw in the RCI digital studio gear. But then a few days ago I heard it again on RCI -- surely the tech-savvy Chinese would not have let this kind of problem persist for weeks.

Today I heard the same effect on a very different SW station -- this one an the 24/7 fire and brimstone broadcast that appears at many points on the dial. The effect is very similar to what I heard on RCI.

So OK all your shortwave gurus: What is going on here?

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

http://www.wired.com/wiredscience/2013/08/project-west-ford/

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

Chitika

SolderSmoke Podcast #174:Belthorn III, BITX20(-40), Parasites, Test Gear, Hamfest, SPRAT, Flares, BITX History

Working VK6 Homebrew During the Big Solar Flare

Interesting Propagation Web Site

Radio China International Echo Mystery SOLVED!

Long Delayed Echo on Radio China International

SolderSmoke Podcast #165 Arduinos!

Shortwave Echo Mystery on Yet Another SW Station. What is this?

Dipoles in Space! Millions of them!

AHMED HASSAN MOHAMMED

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