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Discovering little worlds

Like so many other people during the COVID lockdown, I’ve been looking for additional hobbies that could be done from home, which would occupy my time and help keep my mind off the collapse of civilization as we know it, and maybe even ground my thoughts and keep them away from hyperbole and catastrophizing.

While cleaning and organizing my basement I came across this small USB device. It’s barely larger than a flash drive, but it’s no flash drive at all — it’s a software-defined radio (SDR), namely an RTL-SDR V3 dongle.

I don’t even recall how this device ended up in my possession;  I think it was probably from one of my previous jobs:  they were throwing away a bunch of equipment that was no longer useful, and allowed me to keep some of the items.  Regardless, I had never actually used the SDR, and hadn’t really thought about what the SDR would be useful for.  I had a vague understanding that the SDR can let me tune in to any random radio frequency, but how interesting can that be?  Well, it turns out that playing around with this device led me into a rabbit hole of epic proportions.

Once I found the right software to work with the SDR device (SDRSharp for Windows, and CubicSDR for Mac), I was up and running.  The first rather trivial thing to do was to tune in to the local FM radio stations. Here they are, as viewed through a spectrogram:

FM radio

But that’s kind of boring. I wonder what lies outside of the FM radio band? Well, the next obvious destination is the local police frequencies, which are around 460 MHz to 490 MHz in my area. These are narrow-band FM (NFM) stations, so we adjust our software settings accordingly. In mere moments, I’m listening to police dispatchers communicating with units and telling them about robberies, car accidents, and the like:

And of course there are a few local HAM radio repeaters nearby, which tells me that the HAM community is very much alive and well.  Since I can’t transmit anything using my tiny SDR device, I can only listen in on the HAM conversations, but that’s okay since the conversation wasn’t particularly scintillating anyway, and I’m not sure that getting into the little world of HAM radio is really my goal here. As much as I salute the enthusiasts who keep HAM radio going, they can party on without me.

Mind you, all of this was using the cheap tiny antenna that came with the SDR itself.  But then I discovered that the SDR can be used for something else entirely: receiving signals from satellites!

Arguably the easiest satellites to pick up signals are the NOAA 15/18/19 satellites, which are weather satellites that transmit images of cloud cover over the ground. By “easiest” I mean requiring the least amount of additional equipment:  it only requires a rabbit-ear (V-dipole) antenna connected to your SDR, and a cloud-free day to get a good signal. Here is the signal at 137.9 MHz, and the resulting image, which is produced by special software that demodulates the “audio” data that was recorded:

The downside is that these satellites are in a sun-synchronous orbit, and will only pass by your location for ~15-minute intervals at the most, and can only be caught at very early or late hours of the day. The other downside is that the NOAA satellites are aging, and will probably be decommissioned in the coming years. And anyway, the images they transmit are not the highest quality. Time to step it up to the next level, namely the GOES satellites!

The GOES-16 satellite is a newer weather satellite that is geostationary, and is positioned permanently above the Americas. In fact its longitude is almost exactly over the East coast, which is perfect for my purposes, and its inclination from my location is about 45 degrees (because it orbits around the equator, as all geostationary satellites must do).

But because it’s geostationary it’s also much farther away, and therefore its signal is much weaker, and requires additional equipment:

The setup consists of an old WiFi grid antenna, which feeds into a SAW filter and amplifier, which then feeds into the SDR that’s now connected to a Raspberry Pi (the total cost was about $100).  The Raspberry Pi is running a package called goestools which demodulates the signal from the satellite in real time, and translates the signal into images. The satellite transmits images of Earth in many different spectral bands, ranging from visible light to deep infrared.

And so, the final little world I discovered on this adventure is this one:

The full resolution of these images is 10K, which is mind-blowing, and my next step is to create animations from these images, which are sent by the satellite every 15 minutes.

I think I’ll leave this antenna setup as a permanent installation in my house, so that I can grab these signals anytime I like. Even though this imagery is available on the web if you know where to look, there is something profoundly awesome in knowing that you personally can receive selfies of our world, from 35,000 kilometers away, using about $100 worth of equipment. It’s been a very satisfying few weeks, in spite of everything else that’s happening this year.

Thoughts on the new Star Trek

I watched Star Trek: Picard recently, and… I am sad.

Gene Roddenberry had a vision: a future which is truly post-racial, post-war, post-poverty, etc. It’s a world for us to strive towards, to admire, to want to live in.  But the world of Star Trek: Picard seems to have all the same problems we have in the 21st century.  The Federation is a systemically racist organization that refuses to help an enemy in a time of desperate need. There is deep wealth inequality between different classes of people on Earth. People treat sentient androids like property. And all of “space” is a hostile battleground where one dares not venture without being armed to the teeth.

That’s not a world I look forward to living in, and it would be depressing to me if this is how humanity “turns out” in three hundred years.

Aside from pontificating about today’s political issues, the show’s plot is completely incoherent, and the writing is so lazy and unfocused. Remember Picard’s caretakers at his château who were former Tal Shiar? Those were some interesting characters, but will we ever see them again? Was there any point in having the Borg involved in the story at all? Does the Romulan Samurai kid (bet you can’t think of his name!) have any purpose than to chop people’s heads off? Will Agnes’s murder of Bruce Maddox be swept under the rug? Will the fact that Picard is now a synthetic golem ever be mentioned again?

One perfect example of lazy writing is embodied in the hand-held purple repair device that the Androids conveniently give to Captain Rios. This device basically grants wishes: you can wish it to repair your broken warp core! Or you can wish it to create a mirage of a hundred starships, complete with warp signatures that can fool Romulan sensors! What luck!

And think about how Old Trek and New Trek are different in terms of fandom. There are fans who transform their basement to look like the bridge of the Enterprise. There are fans who program their desktop computer to look like an LCARS interface. And of course there are countless fans who attend conventions dressed up like characters from the Original Series and Next Generation. But will there be any fans who’ll want to recreate the bridge of Captain Rios’s ship (bet you don’t know what it’s called)? Will there be any fans who will admire or want to emulate any of these new characters?

Is it possible anymore to have a show where the whole universe isn’t about to blow up all the time? Can we just have a show where the Enterprise goes to a planet, and Picard negotiates a peace accord, while Data and Geordi get into a wacky holodeck adventure?  I ask for so precious little!

Reverse engineering a 25-year-old Visual Basic app

Following up from last week’s misadventures with the Avant Stellar keyboard (trying and failing to extract macro information from the keyboard’s internal memory), there was another glimmer of hope:  my friend found a backup file that possibly contains all the macros that were saved to the keyboard.  If I could just reverse-engineer this backup, we could extract the macros directly from the file.  It is a 2 KB file with a .KBD extension, unrecognizable as any binary format I’ve seen to date. Here is a partial hex dump of the file:

It’s pretty clear that the file contains a key mapping, as evidenced by the list of incrementing 32-bit numbers at the beginning, up to offset 0x210.  There are roughly 120 increasing numbers, which is roughly the number of keys on the keyboard, so we can safely assume that this is the key mapping.  After the key mapping, I presume, comes the macro information, and this is where things get tricky, since there’s virtually no way to tell how the macros are encoded in the file. The data simply looks too general to make sense of.

An obvious possibility would be to “load” the backup file into the Avant software tool that came with the keyboard, and visually inspect the macro(s) assigned to each key.  But no matter what I tried, the software would not load the file.  Or rather, it loaded the key mapping, but not the macros.  Time to think about the nuclear option: disassemble the Avant software and see how it’s actually processing the backup file.

Looking at the folder contents of the Avant software tool, I immediately notice a dead giveaway: VBRUN300.DLL, which means this tool was written in Visual Basic 3.0.  This makes our job much easier, because there are actually ready-made tools for decompiling Visual Basic executables. (If you recall, Visual Basic compiles executables into p-code instead of native machine code, which makes them much more straightforward to decompile.)  All of this took me quite a while to remember, because I hadn’t used these tools since my early, early hacking days, and it took a little while longer to find them in my archives!  The go-to utility for performing this task was literally called VB3 Decompiler, and the way to find this tool on the web today is… outside the scope of this post.

The decompilation basically results in several Visual Basic source files, in which the original function names are intact, but the local and global variables are changed to generic identifiers, since those names are not stored in the compiled code. It takes a little bit of further massaging to get these files to actually build within Visual Basic, but after that, it’s almost as if you have the original source code of the program at your fingertips.

There was one other minor hurdle because the Avant software uses custom UI components (.VBX files) that don’t allow themselves to be used in Design mode (as part of a copy-protection or licensing mechanism), but this is bypassable using another utility in the decompiler suite that “fools” Visual Basic into loading the components anyway.

With the source code buildable and debuggable, we can now easily run the program and load the .KBD backup file, and trace through where it processes the data in the file:

Even though the variable names aren’t very descriptive in the above screenshot, it’s easy enough to spot the loop that deserializes the keyboard macros, and how each macro is composed.  Not only that, but we can determine what was preventing it from displaying the macros in the first place — it turned out that it expects the keyboard to be physically connected while running, and while I’m pretty sure that we tried loading the backup with the keyboard attached, it wasn’t working anyway, probably because the keyboard is malfunctioning and no longer able to communicate properly.  But at last, with this requirement bypassed, the macros that were loaded from the backup file finally reveal themselves:

Confirmation dialogs

Recently a friend of mine contacted me with an interesting issue.  He got ahold of a keyboard from an old PC workstation used with some legacy accounting software. But this was no regular keyboard — it was an Avant Stellar keyboard, in which all of the keys were remappable, and any key could be programmed with custom macros.

The original owner of the keyboard was no longer at the accounting firm, but my friend was very interested in determining what macros were assigned to each key, so that the accounting firm could use the old software more effectively, and hopefully transition away from it more easily.

I helped by managing to dig up the original software that shipped with these keyboards, which worked with MS-DOS and older versions of Windows. Here is what the software looks like:

Clearly this software is where the user gets to create their own macros and remap all of the key bindings. No less clearly, the software allows us to “Upload” and “Download” the mappings.  So, naturally, my friend thought the most sensible action would be to “Download” the current state of the keyboard and view all the macros in the UI of this software tool.  And so, he clicked the Download button, and… nothing seemed to happen. After a brief progress message, the interface stayed the same.

Now here’s the question: What does “upload” and “download” mean?  In 2020, download generally means “fetch something from an external source and save it onto the computer,” and upload means “send something from the computer to an external source.”  And you might think, in the context of this keyboard, download means “retrieve the current state of the keyboard onto the computer”…

But sadly, twenty years ago, the programmers of this software had the opposite definition of “download” in their minds.  Downloading meant loading the current mappings from the software onto the keyboard!

And even more sadly, the programmers didn’t include a prominent confirmation dialog that says, “CAUTION: this will load the new mapping onto the keyboard and overwrite any previous settings!”  And with a single click, the keyboard was overwritten without any warning or backup.  The only thing the programmers did was include a tooltip that appears when hovering over the Download button:

…but the tooltip appeared only after it was already too late.

Recovering data from QIC-80 tapes: another case study

In another of my recent data recovery cases, the patient was a QIC-80 (DC 2000 mini cartridge) tape that was in pretty bad shape. From the outside I could already see that it would need physical repairs, so I opened it up and found a harrowing sight:

The problem with QIC cartridges in general is that they use a tension band to drive the tape spools. If you look at a QIC cartridge, it’s completely enclosed, except for a plastic wheel that sticks out and makes contact with the capstan mechanism when it’s inserted into the tape drive.  The flexible tension band is tightened in such a way that it hugs the tape spools and drives them using physical friction.

This tension band is a major point of weakness for these types of tapes, because the lifespan of the band is very much finite.  When the tape sits unused for many years, the band can stiffen or lose its friction against the tape spools, which can result in one of two scenarios:

The tension band can break, which would make the cartridge unusable and would require opening the cartridge and replacing the band. This is actually not the worst possible outcome because replacing the band, if done properly, isn’t too disruptive of the tape medium itself, and usually doesn’t result in any data loss.

A much worse scenario is if the tension band becomes weakened over time, such that it no longer grips the spools properly, so that the next time you attempt to read the cartridge, it will spin the spools inconsistently (or cause one of the spools to stall entirely), which will cause the tape to bunch up between the spools, or bend and crease, creating a sort of “tape salad” inside the cartridge, all of which can be catastrophic for the data on the tape. In this kind of case, the cartridge would need to be disassembled and the tape manually rewound onto the spools, being extremely careful to undo any folds or creases (and of course replace the band with a new one, perhaps from a donor tape). This will almost certainly result in loss of data, but depends greatly on the degree to which the tape was unwound and deformed.

Note that the tape drive that is reading the tape is relatively “dumb” with respect to the physical state of the tape. It has no way of knowing if the tension band is broken, or if the tape isn’t wound or tensioned properly, or if what it’s doing is damaging the tape even further. Great care must be taken to examine the integrity of the tape before attempting to read it.

With this cartridge, it’s clear that the tension band has failed (but didn’t break). The tape has obviously bunched up very badly on both spools.  Less obviously, the white plastic wheels at the bottom show evidence that the tension band has degraded, with bits of residue from the black band being stuck on the wheels. The fix for this cartridge was to remove the bad tension band, clean the white plastic wheels, respool and tighten the tape, and install a new band from a donor tape. After the procedure was complete, more than 99% of the data was recovered. The tape header was readable, as were the volume tables. Only a few KB of the file contents were lost.

Therefore, when recovering data from very old QIC tapes, it’s probably a good idea to replace the tension band preemptively with a known-good band, to minimize the chance of breakage and damage to the tape. This is why I keep a small stockpile of new(er) tapes from which I can harvest the tension band when needed. At the very least, it’s a good idea to open up the cartridge and examine the band before making any attempts to read data from it.