Trimming the fat from my wardriving setup

As you may remember, several weeks ago I wrote about my soon-to-be wardriving setup that centered around my new TW700 Winbook. I had a cheap USB hub, a TP-Link dual-band Wi-Fi stick, and an EM506 GPS receiver.

I finally took some time on Saturday to get rid of the fat, i.e., all the individual plastic housings, the USB connectors themselves (physically large and limited my layout options), and am about to repackage the whole thing into a single weathertight enclosure that can either be attached via magnets to the top of the rental cars or carried in a backpack/fannypack as I walk around an area.


Here’s the setup without all the excess plastic. The GlobalSat EM-406A (SiRF Star III) modular GPS is at the left, with its built-in antenna the white/beige square; the TP-Link dual-band Wi-Fi dongle has been reduced to just the board, and as well I removed the USB connector to reduce the length; the USB hub has had the two dual-port USB assemblies removed to reduce height; and all the former USB connections have been reduced to bits of ribbon cable. The TP-Link dual-band antenna is quite good and so I’ll be keeping that. The 3′ USB hub cable still needs to be replaced with a 6′ version, and I think I’ll remove the RP-SMA connector from the side of the TP-Link and directly connect the coax to the board.



The most difficult thing so far has been removing the excess USB paraphernalia and cleaning up the board. To that end, yesterday I bought a new tip for the soldering station, and more 63/37 solder. I use a solder sucker to remove the existing solder, but have found it’s quite difficult with the RoHS solder used nowadays. The 63/37 solder seems to dilute the RoHS solder and make it easier to remove with the solder sucker.

Today I’ll finish this up and put it in an enclosure.


The Deep Space Network

In 1985 I had the opportunity to travel around the world for the NASA Deep Space Network (DSN). Left LA the last day of June, didn’t return home until mid-September. Along the way got to see some neat things, including the Southern Cross, the Magellanic Clouds, the lack of a southern polar star, kangaroos, more cockatoos than I’ll ever need, and the other two Deep Space Stations, DSS-40 (Tidbinbilla, Australian National Territory) and DSS-60 (Robledo de Chavela, Spain).


In the above picture of the site at Tidbinbilla, the 64 m dish is center right, while the 34 m HA-DEC (hour angle / declination) dish is to the left. The 64 m dish was subsequently embiggened to 70 m. The HA-DEC antenna is long gone. This JPL site discusses the advantages and disadvantages of the HA-DEC.

My trip was to lead the installation and test of the Base Band Array (BBA), two “NASA-blue” 7′ high rack-fulls of a state-of-the-art signal-processing system that would allow the real-time combining of received radio signals from each antenna at a site, and provide nearly the full signal gain that was possible. The BBA digitized the baseband signal from each antenna, then ran it through a correlator, and summed together the signals.  Given that each DSS had a 64 m, 34 m, and at least one 26 m dish, it was possible to get nearly 1.6 dB gain over the 64 m dish alone. I think we were able to achieve better than 1.5 dB.

Why go to all that trouble for a measly 1.5 dB? Voyager 2 was on the extended grand tour phase of its trip, and emerald Uranus was coming up in 1986. That extra gain meant more images and science data coming back from Uranus!

More on the Deep Space Network is available here, including a little narration from my former section manager, Dr Al Bhanji!

Decoding not one, not two, not three, but four ACARS channels on one USB SDR Stick!

ACARS (Aircraft communications and reporting system) monitoring has never been easier. Used to be one had to set up an AM aviation receiver or scanner and feed the audio output into a computer soundcard to receive and decode the 2400 baud ACARS packets. As well, since there are well over a dozen possible AM VHF aviation/airband channels where ACARS might be found, it was a real nuisance to scan. Even fast scanners listening to only a few radio channels could capture only a portion of the messages transmitted. Not any more!

Now acarsdec is available, and works incredibly well. An extremely neat feature is its ability to listen simultaneously (not sequentially, but really in parallel) to up to four channels in any 1 MHz piece of radio band, decode all packets heard and UDP them to an Ethernet address of your choice.

I used to have two Radio Shack PRO2052 scanners, each monitoring 4 ACARS frequencies, a sound card for each, as shown on the right in the following diagram from 2006.

N7UV_Main Station_ACARS-APRS

Back then, the antenna was a pair of dipoles, one horizontal, the other vertical, with a 90° phasing line in-between, providing an antenna with circular polarization for improved reception. I tested acarsdec against a scanner monitoring the same 4 channels, and acarsdec won hands-down.

Since acarsdec can monitor only 1 MHz continuous spectrum, I’ve set one up to listen to 136.700, 136.750, 136.800, and 136.850 MHz ACARS channels. The vast majority of traffic is on 136.850 MHz, but every once in a while I hear something on the other ones. I wish I could monitor a set of channels spaced more widely, but this is pretty darned good as it is!

A Looney Tunes Tribute on an FAA Plate

The statement, famously spoken by Tweety Bird, is immortalized on the GPS Rwy 16 approach for Portsmouth NH airport KPSM.

“I tawt I taw a puddy tat”

Spelled out over 4 waypoints on the approach!


And if one misses the approach and needs to go in a hold, there’s IDEED, as Tweety always(?) follows the aforementioned with the exclamation

“I deed, I deed taw a puddy tat”

Nothing nearly as interesting here in Arizona, where we have lots of references to baseball, hockey, football, golf, desert animals and plants, and the weather.

And darkly and non-sequiturly, if the aviator approaches from the NE, they’ll have to pass through SATAN…

Cool USB voltmeter/ammeter

It’s a sweet little gadget, good for measuring the USB port supply voltage and current being consumed by things plugged into the USB port (like my new Winbook TW700).


Even better, the price including delivery via China Post was about $3.50.

With this nifty gadget, I now know that my the Winbook (when on but completely charged) is pulling about 0.41 A.


I checked it with a load built out of 1% resistors and it seems pretty darned close. This should be in everyone’s toolbox.

Winbook TW700 and Warwalking / Wardriving

This is an amazing little gadget. And an amazing bargain if you play your cards right. The Winbook TW700 has been out for a while, and I learned about it only recently through an APRS reflector post from WA8LMF TW700 Review.

It is a simple Windows 8.1 machine, available only at MicroCenter, and there’s no MicroCenters here in Arizona. However, fortunately I have been traveling to Chicagoland on occasion and there are a couple of MicroCenters there.

Searching the MicroCenter website for pricing on the TW700, it ranges from about $44 to $80, depending on whether it’s new, open box/returned, or bare units without the accessories. And stores only have whatever is available in their store, so you might walk in and find that only new units are available, or they might have a number of open boxes, etc. I was very fortunate to get one at a good price, open box, and I didn’t need the few cables and charger that the new ones come with.

Like I said, these are extremely simple Windows 8.1 tablets, and quite tight on expansion. The one that I picked up had a 32 GB microSD card installed, which has turned out to be quite handy. Also, there’s only 16 GB of permanent storage in the machine, so Windows 8.1 takes up about 6 of that, and there’s about 8 GB in a restore partition. So there’s very little extra storage in the inboard “drive”. There’s also only 1 GB of RAM, and that can be tight unless you have low expectations. The Atom processor is plenty fast, and the screen bright and easily readable. The whole thing can run off its internal battery for hours at a time (maybe 4?).

Through WA8LMF’s and others’ web postings, I was able to increase slightly the available storage on the inboard drive even after the zillions of 8.1 updates that ballooned the size of the base Windows configuration. I have about 2 GB of inboard drive storage available now, which is plenty for my applications.

Speaking of applications, the main reason I got this was that I’m into wardriving using Vistumbler and WiFiDB, excellent tools written and supported by Andrew Calcutt and Phil Ferland. For a while, when working or visiting somewhere without my truck and its built-in Vistumbler wardriving setup, I had to make do with a notebook PC and its built-in dual-band Wi-Fi, and my Garmin GPS jacked in to the PC USB port. Was very bulky, and difficult to observe the results in real-time.

The TW700 changed all that. I also got a $10 USB hub (the TW700 has one regular USB port), a GPS receiver board from Sparkfun, and a very inexpensive TPLink dual-band Wi-Fi USB dongle. Borrowing a better dual-band antenna from the junkbox, I now have a pretty competent pedestrian/mobile warwalking/wardriving setup.


This is an incredible little warwalking setup. I’ve even rode the bicycle around with this in the backpack, and it is really a nice performer. I taped the TPLink dongle / dual-band antenna to the top of the truck, across from my big Cisco dual-band antenna feeding the truck’s wardriving setup, and got essentially the same results while driving the neighborhood. Excellent sensitivity and lots of access points. The TW700 runs smoothly and supplies enough power to run both the GPS and the Wi-Fi dongle, so I didn’t have to bring along an extra battery to run the hub.

I still have to package the TPLink dongle, GPS and the USB hub together in a single package, so that there’s only the USB cable to the TW700.

You can read more about wardriving, Vistumbler, and the WiFiDB at the techidiots forum.

ADS-B and PiAware

I’ve been experimenting with PlanePlotter, acarsdec and a bunch of other things recently, and have had to hack my way to a whole new level of incompetence with Linux in the form of Raspbian.

One important thing I just learned was the system flow diagram for dump1090 and piaware.

At least now I understand better how messages flow within my setup here, and am starting to learn more about the different ports on dump1090 and piaware, and how mlat (multilateration) works using the aggregation of other piaware receivers through the FlightAware servers.

PlanePlotter, however, is a whole new can of worms, perhaps interesting worms, but worms, nonetheless.