A Very Busy Christmas Weekend/Eve For Pirates

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Here’s what folks have been hearing since Friday night. 41 different North American pirate radio transmissions so far, a total of 163 loggings, and it’s not even Christmas yet!

A big thank you to the operators for their shows, and the listeners for their reports.

All of these loggings can be viewed at the HF Underground

Pirate Radio Boston 6925 AM 1945 UTC December 24, 2012
WBNY 6240 AM 1604 UTC December 24, 2012
Eccentric Shortwave 6930 USB 1529 UTC December 24, 2012
Channel Z 6925 AM 1400 UTC December 24, 2012
UNID 6925 USB 1455 UTC December 24, 2012
Metro Radio International 6975 AM 1323 UTC December 24, 2012
Radio Ronin 6920 AM 1308 UTC December 24, 2012
Northwoods Radio 6925 USB 1200 UTC December 24, 2012
Channel Z 6925 AM 0427 UTC December 24, 2012
UNID 6955 AM 0212 UTC December 24, 2012
Rave On Radio 6925 USB 0200 UTC December 24, 2012
Radio GaGa 6925 USB 0140 UTC December 24, 2012
Radio Appalachia 6935 AM 0125 UTC December 24, 2012
Dit Dah Radio 6925 USB 0025 UTC December 24, 2012
Dit Dah Radio 6935 USB 2156 UTC December 23, 2012
WBNY 6913.34 AM 2150 UTC December 23, 2012
WKND 6924.6 AM 2148 UTC December 23, 2012
Metro Radio International 6925 AM 2008 UTC December 23, 2012
WEDG The Edge 1610 AM 1700 UTC December 23, 2012
Pirate Radio Boston 6925 AM 1612 UCT December 23, 2012
Pirate Radio Boston 6950 AM 1610 UTC December 23, 2012
Pirate Radio Boston 6925 AM 1805 UTC December 23, 2012
Channel Z 6925 AM 1346 UTC 23 December 23, 2012
1720 KHz “The Big Q” 0509 UTC December 23, 2012
Channel Z 6925 AM 0405 UTC December 23, 2012
WPOD 6925 USB 0130 UTC December 23, 2012
Wolverine Radio 6925 USB 0048 UTC December 23, 2012
Toynbee Radio 6925 AM 2258 UTC December 22, 2012
Monkey Mayan Memorial Radio 6925 AM 2222 UTCDecember 22, 2012
UNID 6950 USB 2218 UTC December 22, 2012
UNID 6924.7 Khz AM 2215 UTC December 22, 2012
Toynbee Radio 6925 AM 2131 UTC December 22, 2012
Pirate Radio Boston 6949.39 AM 2015 UTC December 22, 2012
UNID 6935 AM 1902 UTC December 22, 2012
Pirate Radio Boston 6949.39 AM 1355 UTC 2December 22, 2012
Rave On Radio 6925 USB 1241 UTC December 22, 2012
The Big Q 1720 & 1710 AM 0525 UTC December 22, 2012, 2208 UTC
Captain Morgan Shortwave 6950.7 AM 0240 UTC December 22, 2012
UNID 6925 AM 0225 UTC December 21, 2012
UNID 6924 AM 0203 also 6929 AM 0207 December 22, 2012
Insane Radio 6925 AM 0121 UTC December 22, 2012
Insane Radio SSTV 6925 AM 0021 UTC December 22, 2012

WWV and WWVH Via Both Long and Short Path on 15 MHz and I can Hear Russia From My House

In Measuring The Distance To A Shortwave Radio Station we looked at how the propagation delay in a shortwave signal can be used to estimate the distance to the station.

I ran some more tests the other day:

Below is a recording of 15 MHz, taken at 2300 UTC on December 13, 2012:

The GPS 1 PPS reference is on the top trace, and the audio from the radio is on the lower trace.

You can see the one second tick pulse from WWV in the audio, as well as two pulses from WWVH, the first (weaker) one is the normal (short) path signal, and the second one is via long path. We can confirm this is the case by converting the time delays into distance. We’ll use the same formula as in the previous article, we subtract off the 286 sample delay from the radio, multiply by 22.676 to convert the delay in samples to microseconds, then multiply by 0.186282 (the speed of light in miles per millisecond) to convert the delay into miles.

For WWV, the measured delay from the 1 PPS pulse is 660 samples. (660-286) * 22.676 * 0.186282 = 1580 miles
For WWVH short path, the measured delay was 1516 samples: (1516-286) * 22.676 * 0.186282 = 5196 miles
For WWVH long path, the measured delay was 5080 samples: (5080-286) * 22.676 * 0.186282 = 20250 miles

The distance to WWV is 1480 miles, and to WWVH is 4743. The long path distance to WWVH is 20158 miles.

Remember, the calculated distances can be longer than the great circle distance, due to the signal making one or more (many more in the case of long path) hops between the Earth and the ionosphere. Plus, there is the experimental error.

And here is one more example, this time it is the Russian time station RMW, on 14996 kHz, recorded at 1157 UTC on December 10, 2012:

The delay was 1835 samples: (1835-286) * 22.676 * 0.186282 = 6543 miles.
The great circle distance is 4821 miles.

Measuring The Distance To A Shortwave Radio Station

In a previous post, I showed how it was possible to crudely measure the speed of light (or at least another type of electromagnetic radiation, radio waves, in this case) by measuring the time delay between two shortwave radio time stations, WWV and WWVH.

I’ve decided to re-do that experiment, but in a slightly different way. Rather than measure the speed of propagation, I will use that speed to determine the distance to the radio station.

Various time stations transmit precise time on several shortwave frequencies. Here in the USA, we have WWV in Ft. Collins, Colorado, which transmits on 2.5, 5, 10, 15, and 20 MHz. We also have WWVH in Kekaha, Hawaii, which transmits on 2.5, 5, 10, and 15 MHz. These stations transmit an audio “tick” at exactly each UTC second. There is also the Canadian station CHU, located near Ottawa, Ontario, which transmits on 3330, 7850, and 14670 kHz.

One way to measure the speed of radio waves (and light) would be to measure how long it takes for the tick to travel a fixed distance. Divide the distance by the time, and we have the speed of light. However, that requires knowing the exact UTC time locally. This can be done with a GPS unit that outputs a 1 PPS (pulse per second) signal.

How to feed these signals into the computer, so they can be measured? The radio audio is easy enough, feed it into the sound card. It turns out the 1 PPS signal can also be fed into the sound card, on the other channel. I used a capacitor to couple it.

The first measurement that is required is one to determine what time delay is added by the radio electronics. In my case, I was using a JRC NRD 545 receiver, which has DSP (Digital Signal Processing) to implement the audio filters. This certainly adds a time delay. I therefore needed to run some baseline measurements, to determine how long this delay was.

I fed the same 1 PPS signal into the antenna jack of the radio. The signal is a short (10 microsecond pulse) that is rich in harmonics, so it produces a noticeable “tick” sound every second. I then recorded the audio from the radio, along with the 1 PPS signal fed into the other channel, and obtained this data (click on the graph to enlarge it):

I measured the time delay between the two ticks, and found it to be 286 samples. At 44.1 kHz, each sound sample is 22.676 microseconds. Multiplication gives us the time delay, namely 6485 microseconds. This delay added by the radio is constant, provided I do not adjust the IF filtering parameters (which were set to USB mode, 4.0 kHz wide, for all tests).

Next, the antenna was reconnected, an the radio tuned to 15 MHz. At this time of the day (about 2100 UTC) it is possible to hear both WWV and WWVH. Here’s the sound recording:

The WWV pulse occurs at about 5.18 seconds on the recording, and WWVH, much weaker and harder to see, at about 5.2 seconds.

The delay for the WWV pulse is 657 samples. Subtracting the radio delay of 286 gives us a delay due to propagation of 371 samples. Multiplying by our conversion factor of 22.676 microseconds per sample gives us 8413 microseconds.

Light (and radio waves) travel at 186,282 miles per second or about 0.186 miles per microsecond. For the metric inclined, that’s 299.792 km/sec or 0.300 km per microsecond. So multiplying our time in microseconds by the distance light travels each microsecond gives us the distance:

8413 * 0.186 = 1567 miles (2522 km)

The actual distance, along the Earth’s surface, from my location to WWV is 1480 miles, or 2382 km. Why the discrepancy? The radio waves do not travel along the Earth’s surface, but instead are reflected from the ionosphere, which is several hundred miles up. This means the actual path they take is longer. We’ll try to take that into account, a little further down.

The delay for the WWVH pulse is 1550 samples. Subtracting the radio delay of 286 gives us a delay due to propagation of 1264 samples. Multiplying by our conversion factor of 22.676 microseconds per sample gives us 28662 microseconds. We’ll do our next multiplication again, to convert to distance:

28662 * 0.186 = 5339 miles (8592 km)

The actual distance from my location to WWVH is 4743 miles, or 7633 km.

Next, here’s a recording from the Canadian time station, CHU:

The delay for the CHU pulse is 401 samples. Subtracting the radio delay of 286 gives us a delay due to propagation of 115 samples. Multiplying by our conversion factor of 22.676 microseconds per sample gives us 2607 microseconds. We’ll do our next multiplication again, to convert to distance:

2607 * 0.186 = 486 miles (782 km)

The actual distance from my location to CHU is 407 miles, or 656 km.

Now let’s try to take into account the actual path of the radio waves, which get reflected off the ionosphere. We need to know the height of the ionosphere, which unfortunately is not constant, nor is it the same over each part of the Earth. Here is a map showing the approximate height, while the above recordings were taken:

In the case of the path to CHU, the height is about 267 km, or 166 miles.

We also need to determine the straight line path between my location and CHU, through the Earth, vs the distance along the Earth’s surface. This can be calculated, and it is 391 miles, or 629 km.

We’ll determine what the actual path length is for a radio signal traveling this distance. It looks like a triangle, with a height of 166 miles, and a base of 391 miles. We need to determine the other two sides to find the total path length. All we need to do is take half of 391 miles, which is 195.5 miles, square it, add to that 166 squared, and take the square root, then double our answer. The result is 513 miles, which is very close to our measured value of 486 miles. We’re off by a little more than 5%.

Next let’s try WWV: The actual distance is 1468 miles or 2362 km. Doing our math, using an approximate FoF2 ionosphere height of 246 km (153 miles): Half of 1468 miles is 734 miles, we square that and add to 153 squared, and take the square root, and double our answer, getting 1500 miles. Our measured distance was 1567 miles, so we’re off by less than 5%.

Next, the case of WWVH. This is more complicated, as the signal probably is making more than one “hop”, that is, it is going up to the ionosphere, reflected down to Earth, and then reflected back up again, and down again. This may possibly occur multiple times.

We’ll try doing the math anyway. The actual distance is 4588 miles or 7383 km. Doing our math, using an approximate FoF2 ionosphere height of 253 km (157 miles): Half of 4588 miles is 2294 miles, we square that and add to 157 squared, and take the square root, and double our answer, getting 4598 miles. Our measured distance was 5339 miles, an error of 16%. But again, we don’t know how many hops there were. Still, not a bad effort.

Does anyone else have a GPS receiver with a 1 PPS output? If so, I’d like to hear from you, I have some additional experiments in mind.

Mysterious Ditter Network

First observed two days ago, there seems to be a new (to us HF listeners, anyway) network of HF ditter CW transmissions. The purpose of this network, as well as who is operating it, is unknown. It is possible they are for propagation monitoring. Based on observations of listeners and propagation characteristics, it would appear that at least some of the transmissions are coming from North America, possibly the Central US.

The transmissions do not occur at the same time on all frequencies. It appears that each transmitter steps through the frequencies. The following image shows the received signal on three of the frequencies (click on the image to view it as a larger size):

As you can see, thea transmission on each frequency begins right after the transmission on the previous frequency ends. This data was obtained by running a netSDR receiver in 500 kHz wide I/Q capture mode. The resulting recording file was then demodulated at each frequency of interest.

You can also see the second (weaker) dit on the 11150 tranmsission, that occurs shortly before the stronger main dit. (It is less obvious before the second dit, but you can see it, if you squint)

Each pulse (dit) is 130 milliseconds long, and they repeat every 6 seconds.

Next, the demodulated signal for a ditter transmission on each of the above frequencies is shown magnified, to see the exact times of each transmission.


How to find these transmissions:

I find that using an SDR is the easiest way, as you can observe a large portion of the spectrum at once. I use a 500 kHz wide view, and step through HF, looking for the periodic dits. But you can certainly use any radio. Note that the frequencies are all multiples of 25 kHz. They also sometimes occur in groups of three relatively associated frequencies. There are likely additional frequencies that have not yet been discovered.

If you’re hearing any of these transmissions, or have discovered possible additional frequencies, please let us know with a comment!

Transmissions on the following frequencies have been observed (all in kHz):
5450
5575
6225
6550
6750
7700
8000
8275
8775
8825
8900
8975
9050
9225
10050
10450
10575
10900
11025
11150
11225
11300
12450
13100
13250
13325
13875
14400
15100
15400
15625
16000
16350
16550
16725
17475
17650
17950
17975
18050
18100
18200
18450
18625
19300
19650
20100
20175
20250
22050
24050