brainwagon "There is much pleasure in useless knowledge." — Bertrand Russell

28Sep/080

SpaceX launch reaches orbit…

I didn't get a chance to watch the online webcast, but the SpaceX launch of flight 4 of their Falcon 1 launch vehicle managed to reach earth orbit, becoming the first privately developed vehicle to do so. They don't have video up yet, but when they do, I'll try to link it. Congratulations to the team.

Addendum: Here's the Youtube!



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27Sep/080

More spots from W1BW…

Well, I got bored trying to make PSK31 QSOs amidst all the RTTY contesters, so I flipped back to playing with my WSPR daemon. First thing, I got a spot from W1BW with an SNR of -18, so I flipped over to his visual MEPT spotter, and sure enough, here was the clear "MV" beacon. So, I reduced power to 0.5 watts, and tried again. WSPR didn't come through, but you can just make out the MV at the right. That's the difference that 10dB of power makes....

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25Sep/080

Visual Beacon heard by W1BW

Bruce finally got his grabber back online, and I swiped the following image from it:

In addition to the WSPR digital message, my beacon program sends this "MV" at the same time in the visual portion of the MEPT band. Thanks for you grabber Bruce, very nice.

Addendum: Here's a later grab, showing the "flying W" of W1BW, along with my own MV.

Addendum2: Eldon (WA0UWH) up in Monroe, WA (near Seattle) sent me an unprompted, unscheduled reception report, including this screengrab. Awesome. He has the frequency up around 10.140090Mhz, but I think I should probably be about 50hz lower, probably a combination of both of our frequency errors.

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22Sep/080

Another map…

My previous maps of WSPR spots didn't do a great job of showing where my beacon had been heard in the U.S. Here's another try:

Again, still using GMT to draw these.

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20Sep/080

More WSPR developments…

Well, I took a hint from Bruce, W1BW and modified my beacon to do both WSPR and visual beaconing on 30m. Below, you can see the spectrogram of about 16 minutes of recording at my station. The parts with the background nearly black are when my beacon is transmitting. You can see both the WSPR message above and the initial MV below. Each time the WSPR message is sent, it picks a random spot in the 100hz band from 10.140120 to 10.140220 to send in, but the MV remains centered around 10.140030.

Click to see it full size:

This effectively means that I'm only using about half my power for the WSPR traffic, so I probably should rate my transmit power down by 3db.

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14Sep/081

World Map

I'm still playing around with GMT to generate some maps. I'm not sure I've really got it figured out, but here is an attempt to draw a world globe with some of the great circles that connect me to the various stations that have received my WSPR beacon messages.



Addendum: Robert pointed out that I didn't give a link to the GMT tools. Consider this to be the remedy. They are kind of a quirky set of tools that can be used to create very nice output in a number of different projections, but they aren't the simplest to figure out. I first learned about them from the book Mapping Hacks which is well worth owning.

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14Sep/083

Progress on WSPR

So, I've made some progress on teasing apart enough of the encoding of WSPR beacon messages to write a completely stand alone Python program that will generate the appropriate tone sequence to send out the callsign/grid/power message. For instance, if I type "genwspr KF6KYI CM87 27", I get:


3, 3, 0, 2, 0, 0, 0, 0, 3, 2, 2, 2, 3, 3, 1, 2, 0, 2, 3, 0, 0, 1, 0, 1,
1, 1, 3, 0, 2, 2, 2, 0, 2, 2, 3, 2, 2, 1, 0, 1, 0, 2, 0, 0, 0, 2, 3, 0,
3, 1, 0, 2, 3, 3, 2, 1, 0, 0, 2, 3, 3, 0, 1, 2, 0, 0, 0, 1, 1, 2, 1, 0,
3, 0, 3, 0, 3, 2, 0, 3, 0, 2, 1, 2, 3, 3, 2, 2, 2, 1, 3, 2, 3, 0, 3, 0,
2, 0, 1, 2, 2, 2, 0, 0, 3, 2, 0, 1, 0, 0, 3, 1, 1, 2, 1, 1, 0, 0, 1, 3,
0, 3, 2, 0, 0, 3, 3, 3, 2, 2, 2, 0, 2, 3, 0, 1, 0, 0, 1, 3, 0, 0, 0, 0,
0, 2, 0, 3, 3, 0, 3, 0, 3, 3, 2, 0, 0, 1, 1, 0, 0, 2,

Which is the 162 bit long code needed to indicate that KF6KYI is operating with an output power of 27dbM, or 0.5 watts.

If I crank up the power to 37dbm (a full 5w on my FT-817), i should use this code sequence.


3, 3, 0, 0, 0, 0, 0, 0, 3, 0, 2, 2, 3, 1, 1, 2, 0, 2, 3, 2, 0, 3, 0, 1,
1, 3, 3, 0, 2, 2, 2, 0, 2, 2, 3, 0, 2, 3, 0, 3, 0, 0, 0, 0, 0, 2, 3, 2,
3, 3, 0, 0, 3, 3, 2, 1, 0, 0, 2, 1, 3, 0, 1, 2, 0, 0, 0, 3, 1, 0, 1, 0,
3, 2, 3, 2, 3, 2, 0, 1, 0, 0, 1, 0, 3, 3, 2, 0, 2, 1, 3, 2, 3, 2, 3, 2,
2, 0, 1, 2, 2, 0, 0, 2, 3, 2, 0, 3, 0, 0, 3, 1, 1, 2, 1, 3, 0, 0, 1, 1,
0, 3, 2, 0, 0, 1, 3, 3, 2, 2, 2, 0, 2, 1, 0, 3, 0, 2, 1, 3, 0, 2, 0, 2,
0, 0, 0, 1, 3, 2, 3, 2, 3, 1, 2, 2, 0, 1, 1, 2, 0, 2,

My Python program isn't very pretty, and it doesn't implement all the non-beacon message types that are needed for QSO-mode operation, but it does appear to work. I'll make it available after I get a chance to tidy it up a bit more.

Filed under: Amateur Radio 3 Comments
11Sep/080

Off to Yahoo! Hack Day

hackday2008

Perhaps I'll see some of you there.

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8Sep/080

WSPR: Can you hear me now?

I haven't had the chance to type up my notes yet on my attempts at beaconing using WSPR, but I did leave my beacon running off and on for the last week. By monitoring signal reports which appear on WSPRnet.org, I learned quite a bit about how the propagation from my location varied depending on the time of the day. I'll write up a bit more about that as time permits, but for right now, I'll tease you with the following list of sites which gave me at least one signal report:

AB5N, K1JT, K3JV, K3SIW, K3UK, K6RBS, K8PJ, KA2UUP, KA5ULE, KC8JNV, KC8LTD, KC9DOA, KD5JGA, KE7HQY, KS7S, KV6O, N6NR, N7RYW, NJ0U, NN6RF, VE3FWF, VE6OG, VK2GR, VK7RO, W0AEW, W1BW, W1XP, W3CSW, W3PM, W6OUU, W7THY, W8LIW, W9HLY, WA4EWV, WA4KFZ, WA7KQS, WB0NPN, WB3ANQ, WB8ILI, WD6DBM, WD8INF, WT5N, ZL1WN

What might be more revealing is the following map (click to enlarge):

These were all accomplished with a power of 5 watts or less.

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6Sep/080

JH5RXS working contest on 7.0945Mhz

Woke up around 4:00AM, couldn't get back to sleep, so I went downstairs, turned on the radio and caught JH5RXS on 7.0945Mhz booming in. He's Yukio Nishioka, in Japan and 5496 miles off. He was very, very strong: check out the recording. He kept flipping between working split and working on frequency.

Addendum: Apparently this weekend is the "All Asia" contest. Tuning further down the band, JA8NFV calling CQ among others. I couldn't hear most of the hams he was chatting with, but his signal was great. Even further down I heard the JA1YPA contest station.

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1Sep/081

Is this multipath?

While listening to some WSPR signals (and testing my new encapsulated WSPR beacon) I heard some signals that were throbbing at about the baud rate. Instead of a more or less constant carrier, I'd here them swell and fall, swell and fall repeatedly. When I generated a spectrogram, I got this:

You can see a copy of the original signal about 4 Hz higher than the original. Is this an example of multipath?

Addendum: ZL1BLU has a nice page on frequency measurements which describes a lot of the kinds of distortions you might expect to see over an HF path. If I read this correctly, the problem is actually caused by Doppler shifts as the index of refraction in the ionosphere varies over time, causing the frequency to shift over time. If you look carefully at the spectrogram taken of the 16Mhz VNG transmission, you'll see that the received signal varies quite a bit up and down, but also splits rouhgly 1/3 of the way through the signal into two parts, and again at the end. You can also see the keying sidebands, which are symmetric (both above and below). Interesting stuff.

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