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Beacon Reception -- Any Interest?

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Chris Russell

Sun Dec 03 2006, 05:32PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Here's a screencap as of about 1730Z, taken from Dave's stream. The drift appears to be stabilizing.

Dave Marshall

Sun Dec 03 2006, 05:57PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

I forgot about the stream!

This wont play on windows media player, you'll have to get winamp or the like. Amarok and XMMS handle it just fine in linux.

With the speclab plugin you can stream straight from winamp into speclab and decode. You cant actually hear Chris by ear, but he's quite obvious at about 1040Hz on a waterfall.

Dave

Avalanche

Sun Dec 03 2006, 06:25PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

That is awesome, I connected to Dave's stream a few minutes ago and played around with argo

Chris Russell

Sun Dec 03 2006, 06:57PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Excellent work, everyone! I guess technically that's only one reception report, but not bad. From Orono, Maine, to Warner Robins, Georgia. We've had a solid signal for a few hours now, though there is definitely some drift in my transmitter.

The bad news is that my antenna still needs work, as I am transmitting right now into about a 2.4:1 SWR. It pains me to think how much better I might be getting out if I could tune it down to a 1.1:1!

I am going to keep going for a while longer, until the 30m band is dead. If anyone wants to try with their own receiver, rather than Dave's stream, please do. :)

Steve Conner

Sun Dec 03 2006, 07:09PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I've been trying, but never got anything with my own receiver. So I connected my screencap server thingo to Dave's audio stream

ShawnLG

Sun Dec 03 2006, 07:42PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

I am not picking up the signal. I am going to relocate the reciever.

Dave Marshall

Sun Dec 03 2006, 08:10PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

Heres another screen capture. The bands are really opening up, Chris is running a solid 20dB above the noise here.

This screen cap demonstrates the noise rejection capability of the various super slow modes. The bright yellow blurs are a rather discourteous operator using a mode known as THROB. After he got bored and wandered off, he came back again using PSK31, even after a friendly email from me asking him to move over 2khz.

Edit: It doesn't get a whole lot better than this. Getting towards 35dB above the noise. At this point he's actually audible during the peaks.

Below: We switched to qrss3 for a couple minutes. 3 times the data rate, still perfectly readable.

Dave

ShawnLG

Sun Dec 03 2006, 09:27PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

I am not picking up anything but white noize. Does this mean that my mixer is too noizy?

Dave Marshall

Sun Dec 03 2006, 10:25PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

A screen capture showing multiple path propagation in action.

Notice the vertical mirroring, visible particularly on the morse code characters to the left, but on some of the letters as well. This mirroring is caused by the same signal reaching the receiver through different paths. One path is usually more direct, a single skip off a high layer of the ionosphere, and another taking multiple hops (the weaker of the two signals you see there) off a lower layer.

The reason there appears to be a faint ghost is the multiple-hop path is generally subjected to a slightly greater amount of doppler shift than the more direct path.

This sort of propagation is pretty uncommon at solar minimum. Its something you see more often during the peak of the solar cycle.

Dave

Chris Russell

Sun Dec 03 2006, 11:33PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Wow, really really amazing stuff. Thank you so much everyone for all your effort. I am taking the beacon down for now. I want to do a little more testing, and redesign the feed so that I can tune the antenna to a lower SWR. That should enhance my signal a little, and increase the stability, since the finals won't have to disspate 10% of the output RF as heat.

Watching the multipath propagation in action was really a great treat. To Dave's description, I would only add that the doppler shift is caused by the path growing longer, as the ionosphere becomes less refractive at night. As the level of ionization in all layers starts to fall, the signal travels further and further through the ionosphere, higher and higher up, before finally being returned to earth. Both signals are doppler shifted, but the one that passes through the ionosphere more than once experiences a greater increase in path length. It's really interesting and cool that we got to see this happen.

Included below are some of the screencaps I took of Dave's stream. You'll notice that there was some drift evident. The regular up and down drifting was caused by the heater in the apartment, cycling on and off, causing the ambient temperature in the room to cycle up and down. You'll also see that when I first fire up the transmitter, it drifts as it seeks thermal equilibrium.

The transmitter starts up. Signal is weak, lots of drift is evident.

Good eample of thermal cycling.

My signal tries to fight through interference cause by operators who were being inconsiderate, or couldn't hear me.

I adopt Dave's color scheme, and I get to see some multipath doppler shift.

With a final, dramatic shift upwards, and a burst of static, the band gives out for the night. The ionosphere is no longer returning my signals to earth, at least not in Dave's direction.

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