Seeking Comment: Pay Channel Activation Convenience

Let's assume TV broadcasters transmitted both free and pay channels in the air. The pay channels are encrypted with AES-256. This is not like CableCard; each channel has its own code, like Wi-Fi, and the code can change monthly, yearly, or even stay the same forever. The frequency of change is up to the broadcaster.

If you had a Yagi on your roof connected to a "cable" box that could decode the pay channels only if you entered a code mailed or emailed to paying customers, how would you prefer to enter the codes?

1. A keypad on the front of the box, or an onscreen keyboard controlled by the remote. You tune in the particular channel and enter its code, and the box remembers it until it changes.
2. The codes are emailed to you by each individual broadcaster. Using Excel, you copy-paste them into a CSV file, place it on a MicroSD card, and stick it in your box.
3. The codes are mailed on cards as both readable text and a QR code. You connect your (preferably Android) phone by Bluetooth to the box, open a cable box app, and scan the codes, instantly activating each channel, albeit one by one.
4. You have a lightweight, nonintrusive Windows app on your computer. You put in a MicroSD card and click Synchronize. The app has your customer info which you entered during installation. Each broadcaster's server verifies your info and returns the code like Windows activation, but (ideally) minus all the grief. The app loads them all onto the card in a matter of seconds, and you stick it in your box.

I'm open to other suggestions, as well. Tell me your opinion in the comments.

Inmarsat Antenna Comparison

I'm taking a break from Iridium to experiment with Inmarsat. Even though the signals are weaker and require special antennas, I prefer a weaker constant signal to the hopping blowtorch bursts of Iridium.

Recently I built another of Adam 9A4QAV's antennas, this time his tin-can helix. I was just able to discern those relatively wide signals (~168 kHz) shown on killmore231's Imgur page. During a chat I had on #hearsat, @trango informed me that those are BGAN, which is an Internet service.

The next day I found an even wider signal (pictured), which neither @trango nor I could identify. I mention it because it came in pretty strong and I'm willing to bet I could've decoded it, if I had access to a decoder. My tin-can antenna is pretty directional (but not as much as the 10-turn helix), and this signal came in best when I was aimed southwest and pointed high. To my surprise, @trango was able to tell me it came from CONUS Inmarsat at 98W.

I'll provide a comparison of the helix antennas I've tried.

#1 (Okay): 9A4QAV tin-can helix (YouTube video)

Dimensions may be found in the video's comments.

This is what @trango told me was from CONUS Inmarsat 98W.

#2 (Better): 10-turn helix, steel wire, cutoff steel can ground plane, string suspension

I don't know why the signal is now wider.

This antenna was incredibly directional, maybe to within less than a degree. It took me very long to find the satellite, and when I did the antenna was aimed north (go figure). It was a windy day (this was minutes before a big thunderstorm struck) and the wind wiggling the helix caused it to fade in and out.

#3 (Worst): LHCP helix and 81cm DirecTV dish, indoors aimed at a south-facing window

People on #hearsat told me that a dish setup was the very best, but after this kind of performance I was in doubt. However, all I had to do was take the setup outdoors (see #3.1) and it outperformed the 10-turn helix.

I have been able to get a better indoor signal (see below), but the signal strength pictured above is pretty typical right now. On #hearsat I found that these are some kind of aircraft signal, I think 3372 kilobit QPSK, but so far JAERO won't do anything with them.



I like that I was able to at least see a signal indoors, but it really works much better outside.

#3.1 (Best): LHCP helix and 81cm DirecTV dish, outdoors

Notice how most of the signals are bright red. I suspect the poor indoor performance is partly due to the tree outside my window, and of course the glass and metal of the window.

I found that the perfect focal distance for L-band is in fact right where the original Ku/Ka LNB was, so you'll notice in the dish photos that that's where the helix is mounted.


No matter what, this wide signal seems to come in much stronger than the numerous ~168 kHz ones on killmore231's Imgur page. If I just knew what the really wide signal was, I'd decode it in GNUradio and publish the [non-personal] details.

Neat tip

I heard on #hearsat that using AM to demodulate QPSK will tell you the bitrate because there will be a spike in the audio waterfall. The frequency of the spike is your bitrate.

Safety Tips

Be very careful when working with steel cans. I managed not to cut myself when I was using tin shears to cut my antennas, but I made the mistake of putting the sharp scrap in the house trash. Days later a piece poked through the bag and got me while I was taking the trash out.

I also decided to wear eye protection since I was stripping steel wire that kept wanting to spring back. You never know what it might stab into...

TV decoding now on Windows

Recently they released GNUradio for Windows. It sounded too good to be true, but apparently it's for real. It needs Windows 7 and up, and is x64-only. I downloaded it and tried it out this morning and was able to decode ATSC with it.

My favorite part of using Windows, apart from not having to wait for Linux to boot, is that you can record to a RAM drive and then select that file in GNUradio without having to copy it to the hard drive (of course, you should stop the recorder first!) The only catch is that you must use double slashes on your output TS filename in GNUradio, or the flowgraph will fail under Windows.

Once they finish CUDA support for VOLK, we can use live IQ from the SDRplay and watch TV as it's decoded.

Links:
http://www.gcndevelopment.com/gnuradio/index.htm
You might want to see the Documentation, since it tells you little helpful things like clicking the GNUradio shortcut in the start menu; double-clicking .py files will not work.

Drives over 2TB on Windows XP?

Before I bought my 8 TB Seagate external backup drive, I did a lot of research to see if it would work under Windows XP. Most sources claim that under no circumstances can XP read a drive over 2.2 TB. The then-price of $250 was a lot to gamble if it didn't work, so I had to know for sure. Fortunately, one source (probably Seagate or their Amazon listing) listed XP among compatible operating systems, so I bought it and it worked perfectly.

Most drives in the past (~1980s through early 2010s) had 512-byte sectors. Recently they've moved up to 4096-byte sectors. How does this help? Because each sector needs error correction codes, and it's more efficient to store 8 sectors' worth of information and error-code it once than to do it 8 times separately. This translates to higher drive capacity. The only catch is that ordinary BIOS-based computers can't boot from them (but they can be read as data drives by a running OS).

Most people argue that Windows XP can't read drives over 2.2 TB because the MBR partition table can only address 2^32 sectors, and since sectors are 512 bytes this means a 2TiB limit. One answer is to use GPT, but XP can't read that, so they conclude that GPT is the only option and hence XP is barred from using big drives. Microsoft's official stance is that XP can't read big drives, although I think this is to encourage sales of their newer operating systems.

The 2^32 part is right, but what these people fail to see is that MBR is addressing sectors, which is an arbitrary measure. Since drives now are 4K, each individual sector holds more, so bigger drives can be used by old operating systems.

This is all well and good if you buy a drive, because it would be pre-formatted. But what if you want to format the drive yourself? You shouldn't do it in an older operating system (probably includes Windows Vista) because, although it will format and be valid, the OS doesn't know to align the partition based on the sector size. Aligning it to an arbitrary offset was fine for 512-byte sectors, but it would slightly reduce performance on a 4K drive. Your partition should be offset by a multiple of 4096. If you want to verify that it is, then (under Windows XP), Click Start, Run, type msinfo32 and press Enter. In the System Information window that pops up, go to Components->Storage->Disks. Find your 4K drive and look for Partition Starting Offset.

One more concern voiced on a forum was that XP would only read the first 2TiB and experience errors on anything higher. I have disproved that by filling my 8 TB drive with about 3 TB of data and doing a search in Windows XP. There were no errors, so I am confident that XP had no issues. Besides, I went through some of the directory structure myself and looked at a few photos from a huge family album that has to have crossed the 2TB mark.

I think I've said enough. Here's a screenshot of the drive in Windows XP.

In a nutshell:

Myth #1: You can't use >2TB drives on Windows XP because they require GPT

Truth: While it's true XP doesn't support GPT, large drives don't need it*, so you're fine.

*Of course, if your >2TB drive has 512-byte sectors then you are out of luck.

Myth #2: XP only supports 512-byte sectors; Microsoft's official stance

Truth: Yeah, right. See first screenshot, in the Bytes/Sector field.

Myth #3: XP will only read and write the first 2 TB and then fail

Truth: No, my full-drive search under XP proves this is false.

I hope this helps the many uninformed people (like myself, previously) who waver over a drive purchase. I have backed up my points with real tests and pictures, not the unconfirmed advice you find on forums.

It's quite refreshing having recently made the switch back to XP.  Its clean, simple interface is unparalleled and the speed of Windows Explorer is amazing, even in the face of huge amounts of data. It's no secret why Windows XP still has nearly 11% market share. A new computer should be coming in the mail soon, and it has Windows 7 x64. I'll use that for things that need modern Windows.

LED TV interference

I was trying to receive some Iridium signals and turned on my TV while I worked. The TV is right beside my SDR and L-band patch antenna. It's an RCA LED TV from 2014, and when the screen came on I got interference all over the spectrum window. I noticed that the lines got weaker when there was less motion, suggesting the MPEG-2 decoder was the culprit. Or maybe it was the LCD controller. Whatever it was, when the TV show's intro briefly showed the static logo, the lines went away completely.

Iridium decoding: almost there

Recently I've been working on getting the Iridium Toolkit up and running. The Iridium Toolkit is a set of Python programs written by the CCC (a German hacking club) to decode whatever comes off an Iridium satellite. In one of their videos they describe how the system is proprietary and how they had to start from scratch, using trial and error to guess how it worked. They've finally figured it out pretty well and have published their findings.

I realized pretty quickly that this was one project my $20 rabbit ears couldn't handle, so I proceeded to build an L-band (1-2 GHz) antenna.

I first tried a helix, but it barely worked. I don't understand it, but I seem to have a knack for building bad antennas, even when I follow directions, so I was not surprised.

Then I tried a patch antenna. I'd heard that these work well on the L-band. I was expecting a small 1.5-inch square like those little GPS antennas, and I wondered how that could possibly work, but I was willing to try. On researching it, I found that it actually needs to be about 7 inches square with a ~4-inch square in the middle. This particular antenna was designed by Adam 9A4QAV. This RTL-SDR Blog post shows his antenna and its performance with the SDRplay. Notice how the Inmarsat signals look like blowtorches. What's most important is that you don't need an LNA or downconverter to make this happen with the SDRplay; it already comes with an LNA and full L-band support.

The instructions for this antenna can be found on another RTL-SDR Blog post. Finally, you should see killmore231's Adam's Imgur page which contains in-depth pictures. I was blown away by the waterfall images. Killmore231 describes how he tried the RTL dongle, HackRF, and SDRplay with this antenna and how the SDRplay beat out all of them by a huge margin.

I proceeded to build his antenna out of aluminum. I cut everything precisely, down to the millimeter. The only thing I couldn't do was solder to it, what with it being aluminum. I instead put some varnished wire through it, connected to the patch, and used a alligator clip to clip to the back plate. The first few times I hooked it up, it wouldn't show any satellite signals, making me think this was yet another dud.

Today, however, I realized that using varnished wire might leave conductive areas that could touch the back and short it out, so I ran a cut alligator clip to the patch, the plastic insulation providing guaranteed protection against contacting the back plate. I still needed an alligator clip to clip to the back plate. Then I hooked it up, leaned it near a window, and was able to get some strong Iridium signals.

Before, I had only gotten vague blue and green smudges, but these are sharp and have red areas. Below I have zoomed in on some of them:

There's no doubt this is Iridium. All this trouble makes me wonder how an Iridium phone's built-in antenna can possibly work. I watched a YouTube video of an Iridium phone in action and it got all the bars using just its little antenna.

I decided to mount my antenna on a pole sticking out of a second-floor window that's 25 feet above the ground. It gets great reception when it's outdoors like that.

I'm close to decoding Iridium but there are a few things I still don't understand:
1. Why do I only get the bursts? Why not the constant signals like in Adam's pictures?

2. Why doesn't Inmarsat show up? When I tune the Inmarsat band all I see is a strong signal that looks like GSM (see below)

3. What is keeping Python from running the Iridium Toolkit? I managed to install the dependencies it needed, like SciPy, but when I run extractor.py it seems to run but gives constant errors. I don't see any output files, either, so I assume it's not decoding anything.

Slovakia, Oman, and (almost) DRM

Yesterday evening I was tuning my SDRplay and heard two unfamiliar stations. One turned out to be from Slovakia and the other from Oman. According to HDSDR's S-meter, they were both S+40. Since I've never heard either country, I recorded them and uploaded the samples. I narrowed the AM filter partway through the Oman recording.







I also set up HDSDR's recording scheduler to record Radio Romania's DRM program when it comes on around 1:30 AM. Every morning I come and play it back to see if I can decode it. I use 38 kHz FM as the recording mode, centered on the signal, so I can play it back as an IQ file rather than audio. This gives me increased flexibility versus an audio file, since I can make minute changes to the tuned frequency and change things like the AM demodulator's AGC.

This morning I found I had gotten a stronger signal than usual. I was so close to being able to decode Radio Romania International's DRM program. (click to enlarge)