WSPRing along at 27 db below the noise....

WSPR is fun. I haven't crossed any ponds yet, but the real- time displays of the reception reports are very addictive:
http://wsprnet.org/drupal/wsprnet/spots
Be sure to click on the map display also.

I was intrigued by the Signal to Noise ratio column, and wondered what the reference bandwidth for the noise was. K1JT's pages show the reference bandwidth is 2500 Hz, and that WSPR can decode signals that are as much as 27 db below that noise.

That's great. I guess I don't have to worry about the lower sideband of my 30 mw signal causing anyone any trouble. It will be very far down in the noise.

Are Diode Ring Mixers Fundamentally Different?

Joop, PE1CQP, and I have been discussing mixer circuits, especially the ever-popular diode ring.
Here is my latest e-mail to Joop. The RSGB diagram for the ring diode mixer appears above.

Joop: I think the way the diode ring mixer works is very different from the way a two diode singly balanced mixer functions. The effect, of course, is the same. But the polarity reversing element introduced by the ring configuration -- it seems to me -- makes this a very different circuit.

Attached is the RSGB Handbook diagram I mentioned. I like it, because you can really SEE how the actions of the diode ring produce the sum and difference freqs (you have to keep Fourier in mind, and imagine the results of filtering).

The two diode circuit simply "chops" the input signal at the rate of the LO. And it would even work in a non-switching mode -- you could, for example, use FETs instead of the diodes and bias them to operate in the non-linear portion of their curves, right? This makes me think that the diode ring mixer circuits (aka "polarity switching mixers" or "commutating mixers") are very different.

73 Bill

Balloon! Project Blue Horizon Reaches Mid-Atlantic

Wow, that's an exciting track. The intrepid radio amateurs at Cornell University have a balloon up over the mid-Atlantic. It is approaching my old stomping grounds in the Azores. Beacons are onboard and reports are requested. Here are some more details:

Balloon Launch - Assist in Tracking

The NS3 group of Cornell University engineering graduate students will launch PBH-9 (Project Blue Horizon) from Lockheed Martin in Owego NY on Sunday evening, 19 Apr 09, at approximately 21:00 EDT (Monday, 20 Apr 09, 01:00UT)

This ARHAB flight (Amateur Radio High Altitude Ballooning) will ascend and then float for up to 50-hours while drifting to the east.

The payload will include a KC2TUA-8 144.390 APRS beacon
(track via (http://findu.com/cgi-bin/find.cgi?call=KC2TUA-8)
and HF CW position report and telemetry downlinks on 7.104MHz and 10.148MHz.

The NS3 PBH-9 team requests distant ground stations receive and report HF telemetry via N2XE@arrl.net including reception UT date and time.

Distant receiving stations are welcome to also submit HF
reception reports to W0RPK@amsat.org for the ARHAB <50mhz href="http://showcase.netins.net/web/wallio/ARHABrecords.htm" target="_blank">http://showcase.netins.net/web/wallio/ARHABrecords.htm.

Additional PBH-9 information including HF telemetry transmit schedule and format is available via
http://showcase.netins.net/web/wallio/ARHABlaunchannouncements.htm.

Flight updates are available from the NS3 PBH-9 team
via http://twitter.com/pbh3.

WSPR Double Sideband Success!

Oh, how sweet it is. Today I finally got my WSPR station working. Before departing for Sicily, I installed a diode ring mixer (supplied by Jim, AL7RV) between my MEPT oscillator and my two stage 50 mw power amplifier. I thought I might have enough audio coming out of my sound card to modulate the transmitter, but I soon found out that I needed more AF. Lazy after a week on the road in sunny and snowy Sicily, I reached into the junkbox and pulled out the guts of an old computer speaker amplifier. Some really ugly jerry-rigging ensued. The amp is now sitting near the TX, powered by its own 9V battery. Looks like I'm getting about 25 mw out, but that's from both sidebands. So I'm guessing I'm at around 10 mw.

Following guidance from Gene, W3PM (whose FB SSB rig inspired this effort), I set my oscillator at 10138700. That puts the upper sideband in the middle of the WSPR band.

Here's my first set of reports:

								Reported		Distance
Date	Call		SNR					by		km	mi
2009-04-19 18:32	N2CQR		-18					DL0TUH		1353	841
2009-04-19 18:32	N2CQR		-24					PA1GSJ		1343	835
2009-04-19 18:30	N2CQR		-19					DL0TUH		1353	841
2009-04-19 18:26	N2CQR		-22					DL0ODX		977	607
2009-04-19 18:26	N2CQR		-30					G8BKE		1519	944
2009-04-19 18:26	N2CQR		-26					PA1GSJ		1343	835
2009-04-19 18:24	N2CQR		-23					PA1GSJ		1343	835
2009-04-19 14:24	N2CQR		-22					M0WQR		1601	995

Hey, is this a first? Has anyone else run WSPR DSB?

Sicily, Mt. Etna... and The Godfather

Here's some Italy travelogue, well, actually Sicily travelogue. Above, our two heroes are seen with the Etna volcano in the background. Etna is Europe's largest active volcano. It was spitting out lava while we were there. The top is currently at about 10,800 feet (3300 meters). (It varies!) We went up to the 8200 feet (2480 meters) level (via cable car). Here is what it looked like from there:
It was COLD up there. We didn't stay long. Within 90 minutes of this picture being taken, the kids were back at sea level, and in the pool at 80F.

Here is a GoogleEarth View. The yellow marker shows the place at which we took the picture of us in the snow. (The Google shots were from May/June 2006).


Those of you who are fans of The Godfather movie will remember this scene:
Well, here we are, in the same place (but without the shotguns):

Francis Ford Coppola filmed most of the Sicilian scenes not in Western Sicily (where the village of Corleone really is) but in the East, near the beach resort of Taormina, in the village of Savoca. The Bar Vitelli is where Michael Corleone met Apollonia's father. Savoca also has the church where Michael and Apollonia began their brief and unfortunately explosive marriage.

We really liked Sicily. It is a beautiful place, rich in history, and with really nice people.

In Sicily

No posts to blog this week -- we are in Sicily, near the Etna volcano.
Beautiful place. Will talk about this in next podcast. 73

SolderSmoke Podcast #105

On #105: 

http://www.soldersmoke.com

Italy Earthquake
WSPR DSB, WSPR MP3
SBL-1 Blues
Clockwork minimalism
QST articles (design, HBR RX)
Marconi
Spring SPRAT
Blog stuff
ECHO-QSO with Mike, WA6ARA
MAILBAG

Happy Easter!