Datawake Scanner Installation

Keeping my ear to the ground…

by Steven K. Roberts

One of the central themes aboard this geeky ship is expanding the sensorium. I’ve always been fascinated by data collection in all its forms… not just sensors that reveal system health or the state of the environment, but real-time information that shifts my awareness into a much larger space than this little boat-lab. Video cameras inside and out, microphones, ship tracking and aircraft positions, telemetry, ROV for exploring underwater, various flavors of radio comms, and a scanner:


Uniden Home Patrol 2 aboard Datawake (click photo for Amazon page, which is where I bought mine)

The feed is rich. Public safety, utilities, work crews, airplanes, ham repeaters, boats… even the comings and goings of the ferries that connect our island to the mainland… all contribute to an overall sense of having my finger on the pulse. I don’t often need this, but I like it… which is justification enough. And during weather emergencies, it provides essential information that is more of a pain to extract with just a marine VHF.

Choosing the Scanner

bc125atFor the past couple of years, I’ve had the inexpensive little handheld Uniden BC125AT with added Diamond RH77CA antenna… quite adequate in the analog-only environment of these islands. It’s not exactly intuitive, but works well… and has “service search” that allows it to scan groups of frequencies even if you haven’t set up locally relevant channels. (This was particularly fun when I took Amtrak down the coast last May to visit Google… I monitored railroad channels for much of the time, and got familiar enough with the train and yard operations that the cabin steward asked me for updates when we got stuck at a bridge malfunction in Portland.) This is the scanner that got me hooked.

But for Datawake, I wanted something built-in… one of the primary design goals here is to eliminate loose fiddly gadgets with random cables and battery management quirks. The project calls for an embedded scanner that interfaces well, is easy to use, handles digital trunking, and is more or less future-proof (at least for my casual needs… I’m not a hard-core hobbyist like the folks who live over in the excellent RadioReference forums).

My default plan for a long time was the BCD536HP, which is pretty much the flagship of Uniden’s scanner line. This would panel-mount well (DIN standard) and has the maximum feature set, but the user interface is deep and complex. I preferred something easy to use, pretty, and readable at a glance.

The Uniden Home Patrol 2 is the beast I chose, and so far I’m very happy with it. There are a few features missing compared to the 536 (no service search, close call mode, or priority scanning), but it makes up for that with an added “Extreme Upgrade” that offers a suite of geeky tools. The user interface is a color touchscreen, it records to an SD card, and it can accept GPS input to automatically scan the local subset of the entire built-in (and updatable) RadioReference database as you travel. My initial learning curve on the associated Sentinel software gobbled an evening, but it’s now running on the NUC and everything works well. So let’s install it in the boat!

Panel-Mounting the Home Patrol 2

The first thing that struck me when I received this is that sticking it on the panel was going to be even uglier than I had anticipated. My usual heavy-duty Velcro method would be sloppy, depending too much on the stability of the battery compartment cover, and I worried that it would wobble enough to be irritating when I pushed on the top-panel controls for power and volume.

But a little bit of research turned up the BCKHP1 mounting bracket, pricey for a simple piece of plastic (and yes, I looked first on Thingiverse to see if anybody had already published an STL file that I could print on the LulzBot). OK, fine, given the amount of time this saves… and boom, problem solved!

There are four cables that had to be routed through the panel, plus an earphone connector that I’ve left available if I want to skip the ship’s audio network. This called for a bushing at each end, tucked out of sight behind the rig thanks to the space provided by the bracket. Let’s define these interconnects.

scanner-mounted-leftSMA connector for antenna input…
 a bit of a pain as it has to make the leap from that delicate connector to the stiff “pipe” that is my LMR-400 feed line. This coax will forever annoy me whenever I pull the Epsilon cabinet out for service, and the solution was to fabricate a little bracket for the N connector, mounted on the back side of the panel behind the scanner (photo above).

2.5 mm Line-level audio output… requiring transition to the more useful 3.5 mm via a jumper cable, which then connects to a transformer-based isolator since the scanner has a completely different concept of “ground” than the audio gear that will be receiving the signal.

scanner-mounted-rightMini-USB for data and power… piped to the Anker 13-port aluminum hub hanging off the Intel NUC that runs all the ship’s Windows-based comm apps (including SDR, Icom front-end, tools for radio programming, digital modes, and of course Uniden’s Sentinel). When starting the scanner, it asks if we will be using the USB connection just for power, or as a data source from the PC.

GPS input (USB Mini 4-Pin)… an odd connector, acquired by hacking a “Rosewill” cable that will lose its other end, then make its way over to a terminal block carrying the NMEA0183 feed from a Garmin puck GPS mounted on the upper deck (also used by other radios, APRS, and the iKommunicate gateway).

In the photos above, you can peek under the body of the scanner where the cables pass through the 19″ aluminum panel. I used Heyco split snap bushings that let me get away with pre-terminated cable, calling for .5-inch holes.

fusion-cutoutYou see that photo above with the scanner mounted next to the Fusion MS-IP700 marine stereo? That thing owns a serious bundle of cabling, which is already integrated into the system and nicely tied down. I kept putting off this installation job, dreading the process of taking it all apart and having to put it together again.

It thus became a bit of an obsession to do the project in situ, and the only tricky bit would be those two half-inch holes. Wailing on it with Makita and twist drill would be sloppy and throw conductive chips everywhere, so the solution was a Unibit #4 Step Drill (along with a paper chute to keep metal out of the MOTU and a shop-vac to make sure). I put blue painter’s tape over the panel, laid out the holes, fixtured the cabinet to keep it from wandering off on its Delrin runners, and had the job done in about 20 minutes:


OK, with that all done and the rig mounted, let’s get a skyhook up and run some cable!

The OmniX Scanner Antenna

All along, I’ve been assuming that I’d install a discone (the venerable Diamond D130NJ). These work from 25-1300 MHz, though being broadband there is certainly no gain to speak of. Also, aesthetically, they scream “SCANNER!”  I was having trouble getting excited about one of these, and kept delaying an order as I prowled for a better alternative.

In some forum I read glowing comments about the DPD OmniX, reportedly an excellent multiband performer and well-made to boot. OK, why not? Let’s try one.

omnix-portThis is an interesting design, with three dipoles… the two X-element pairs of different lengths and the fat vertical body that provides the mounting structure. The coverage is 118-137, 148-175 & 225-900 MHz. I happened to have an obsolete wind sensor mounted on the starboard spreader of my radar mast, so this presented an obvious mounting location. It went up without much difficulty… using concentric split PVC sleeves of two lengths to straddle a step in the post diameter while giving the brackets something that could handle clamping pressure. TV-antenna-style clamps and a chunk of old PVC are not exactly beautiful from a nautical perspective, but it was expedient and I find I’m not embarrassed at all.

rail-base-feedthrough-lmr400The OmniX has a female N connector at the end of a pigtail, which terminates under a blob of white self-vulcanizing Rescue Tape zip-tied to the spreader. From there, it’s the 50-foot hunk of LMR400 that I mentioned… stiff and perhaps not the best choice, but low-loss for the frequency range of interest. This found its way down the mast, under one of the bridgedeck seat structures to parallel the feed line for the radio-check system, then through the upper console to a spot where it could penetrate the pilothouse roof without introducing water. The photo shows my little trick for getting it through that vertical surface… 7/8″ stainless rail bases, with a hole drilled behind at a matching angle. The bottom one is another run of the same stuff to the dual-band J-pole antenna owned by my Icom ID-5100.

magnet-wall-spottingThe only other trick of note was using a pair of .75″ diameter N52 Neodymium magnets to locate the perfect spot to drill through the cabin wall, as it is easy to measure incorrectly and poke a hole where oops damn it you didn’t mean to… but all you do is tape a magnet in place, slap another onto the opposite side of the wall, draw a circle, and go from there.

At the console, cable management gets tricky… the bundles are thick enough that haphazard spill over the back of the desk is causing problems. I’m now building a support structure out of stainless rail, with a long horizontal member spanning the full 8-foot length of the console. Each of the five cabinets has a lacing bar for cable exit on the back near the top, and between the two will be big lazy loops that allow pulling each enclosure out for service. This is particularly urgent with stiff cable like the LMR400 I used here…

The Scanner in Use

I’ve had this buttoned up for a couple of weeks now, and love it… I scan about 70 channels, and can lock any out if they get annoying (or hold on one if it is particularly interesting). It contributes greatly to my sense of connection with the nearby scene; I’ve listened to the drama around a plane crash (everybody OK), marine rescues, medical emergencies, routine operations on the waterfront, and general aviation. It’s nice to have some information feeds besides Facebook… and the interface with my audio network means I can pipe this to the cabin or mix it in with recorded commentary. And when there is a wailing siren or a stray news helicopter hovering about, it’s good to know what’s going on!



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No Pressure – the Maiden Voyage

News from No Pressure (formerly known as Nomadness)

Latest Update: October 16, 2016

Over the past year, while I have been getting settled into Datawake, my previous boat has been getting lots of excellent attention. She has new opening ports and pilothouse windows, extensive repairs, a fresh dodger, new standing and running rigging, a watermaker, electric heads, a life raft, and a meticulous new owner whose engineering career led him to this boat. Around the end of October, with the help of stalwart crew, he will be heading down the Pacific Coast for a layover in San Diego, then continuing through the Panama Canal with the intent of bringing No Pressure to her new home port on the East Coast.

I’ve offered to host a page where his brief updates via satellite can be visible to friends, and this is it. I will update this any time there is new information to pass along (and will do another page with a photo essay of the extensive upgrades referenced above). In this photo, taken as they returned from an easy test sail on January 24, that’s Dick at the helm and Eric on the bow, doubtless thinking: “Put down that damn camera and catch our lines!”

No Pressure returning to dock

Notes from Dick Tasker

October 16, 2016:

We will be leaving from Friday Harbor, San Juan Islands, WA on a sailing trip to San Diego, CA on the first leg of our trip to Venice, Florida via the Panama Canal on our new boat No Pressure, an Amazon 44 pilot house cutter. We plan to leave around the end of October (exact date depends on weather) with a crew of four intrepid sailors: Myself, Eric Lewis (my brother-in-law), Rick Butterworth (a long time friend) and Alfred Poirier (a sailing friend of Eric’s).


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Audio and Comm Console Development

by Steven K. Roberts
October 2, 2016

SKR aboard Maggie E - Sept 2016

Aboard the Maggie E, a friend’s Ranger 27 – enroute to Lopez Island on September 9, 2016

I catch myself doing it again: waiting for closure on some project before writing about it, an old magazine-freelancing habit. Something should actually be done before you publish the details, right?

Of course, this isn’t a single-threaded project. Subsystems and components are interleaved and interdependent, the objectives evolve with technological change (or at least my awareness thereof), and I’m working on so many fronts at once that I am always in danger of having progress overwhelmed by context-switching overhead.

All that is fun, but when it comes to blogging, old habits die hard. This post is an update from the perspective of 10 months aboard Datawake, and is focused on two console zones that are current work-in-progress.


The photos from my late-March Meet Datawake story reveal a stack of traditional audio mixer/equalizer units… basically a big funnel that gathers mono and stereo sources, combines them, processes them with effects and glorified tone controls, and makes them available as a master output for listening, recording via Thunderbolt, or other uses. This is SO boring.

auxbar-edgeActually, it’s worse than boring (marginal hardware quality aside). It’s also architecturally inflexible, and fails to address some of the more interesting applications on the boat. What I really need is a way to connect anything to anything, which is why we designed an elaborate audio crosspoint switching system for the BEHEMOTH bicycle and later Microship project. Those supported up to 8 simultaneous connections among any of 32 inputs and 32 outputs… although the Auxbar system shown in the photo couldn’t mix, distribute, equalize, or do anything other than perform clean, line-level routing (which was awesome).

I assumed during the gestation of this project that I would design a Node X to provide this capability… an Arduino with a long SPI shift-register chain driving a huge bank of latching relays, allowing switching with no “data type” issues (since simple relay contacts are bidirectional and work with audio, video, serial, PTT, sensors, or even lightweight power switching). But while offering essential functionality, this concept was poorly integrated with the mixer stack, so remained on a vague back burner.

But now, problem solved… and in my favorite way! Someone else has already done it really well, so I don’t have to spend a year inventing a partial solution. The folks at Guitar Center Pro were kind enough to accept a return of the unsatisfactory ART and Zoom boxes, then sell me some goodies from MOTU… the 1248 and 16A:

These things are lovely. They certainly aren’t cheap (Amazon 1248, 16A, & 24Ai), but they eliminate an entire development project while adding a rich web-based UI. A future post will explore them in greater detail… they solve that anything-to-anything problem while providing internal mixers, EQ, and Thunderbolt/USB host interface.

Of course, no learning curve or initial implementation is without glitches, and the first problem was that their free companion iPad app says, in the iTunes store: “The MOTU AVB Discovery from MOTU, Inc. finds all MOTU AVB Devices on your WiFi network, whether they are connected via ethernet or a computer with Thunderbolt or USB.” Turns out this isn’t true as stated, though I see its intent; in a system like mine with two MOTU interfaces, their Ethernet ports are tied up talking to each other… and they can’t be seen on the LAN (though they can via USB on the Mac, of course). One would have worked; so would three or more, using the AVB switch that I had to buy after all… and given that, my choice of the Focusrite OctoPre mkII Dynamic to add 16 more ports via ADAT light pipe was unwise since most of its value is in excellent mic preamps that I don’t need. So this goes back too, to be replaced by the 24Ai that I would have gotten in the first place had their marketing been accurate.

Anyway, the net effect of this mountain of professional overkill (worthy of touring bands and concert halls) is that now all my audio devices… about 40 sources and half that many sinks… will converge on this dense region in console zone Epsilon. Many of those are parts of stereo pairs, related to the piano/entertainment/recording; another group are microphones ranging from podcasting to security; a few more are computers; and a large cluster are radios and their various audio interconnects. There’s even a dedicated Pi for streaming to and from the Internet.


(AVB Routing Grid image from MOTU)

So here’s where it gets fun. Wanna talk on the Icom 7300 HF rig? Pull the boom condenser microphone to my face, poise my toe over a PTT foot switch, and tell the machine via app or macro that it’s time to play radio. The output gets routed to headphones, mains, or console speaker… and if I prefer to use the aero headset for noise reduction, well, we can do that too. Anything to anything, not five dangling microphones and at least that many speakers.

Or, perhaps I’m doing a YouTube video, shaping and de-essing my voice through the DBX 286s input channel strip, mixing in audio sources while talking about whatever… hydrophone, exterior mic, engine room sounds, recordings from the Mac or Tascam box, stingers, theme music, interviews, or radio chatter.

Or maybe I’m off visiting somewhere, far from the boat, and the system texts me to report a security violation. Red alert! Connect via VPN, check system status, watch the cameras including recent timeline, and mix together the interior microphones to discover that it was just Izzy batting a spider who was hanging out in front of a PIR sensor. Phew. (I know, spiders and boats… that sounds wrong… the photo below was aboard Nomadness, reminding me to get out more!)

This whole system is in progress now, with many cables yet to be made (and tested). Things like the piano and monitors are easy, but between this massive audio routing/equalization/mixing system and the cluster of radios I need interconnects… and here there be dragons. It starts with the line level from the mix having to become mic (or other “back panel”) level, ventures into the need for isolation of the balanced connection due to widely varying opinions about the meaning of “ground,” then wanders far afield with the need for filtering due to the fiendish nature of RF. I thought I was going to have to cobble together isolation transformers with level-tweaking pads and and then go crazy with ferrites and capacitors, but it seems this has been done well already by W2IHY… with a kit price of $59.


So speaking of the ham shack, let me bring you up to date on console zone Delta and its connected antennas. The N4RVE “maritime mobile” rig is becoming substantial, and my current mechanical packaging project is the somewhat daunting effort to cram five ham rigs into a 6U panel, then park all ancillary stuff on a 4U just above (with 2U of coax patch completing the comms cabinet). There is some bleed-over; the Home Patrol 2 scanner is next to the stereo in the audio cabinet, and the SDR devices (Funcube Dongle Pro and RTL-SDR, as well as a spot for the intriguing UDRX) are all located next door in the networking zone, hanging off the gigabit switch or the Nuc’s USB hub.

The core of this region is the panel o’ rigs, and what sounds like a lot of redundancy is really a nice spread of overlapping functionality (or that’s what we hams tell ourselves to ease the heartbreak of GAS – Gear Acquisition Syndrome):

  • 7300-filterIcom IC-7300 – the flagship of the station, this is a very flexible SDR-based rig that includes HF and 6-meters, with a rich touchscreen-based UI, excellent filtering, support for digital modes and external large-screen display, waterfall, SD card for recording, and lots of other fancy state-of-the-art features. This will be the primary tool, and owns a Diamond HFV-5 at the top of the radar mast (via the coax patch panel, so I can try other things if that turns out to be disappointing).
  • ic-m802Icom IC-M802 – the industry-standard marine SSB rig, FCC type-accepted for the marine bands, and channelized for ease of use. It works fine for ham radio, but has almost no knobs to twiddle and is kind of boring when you want to dig deep into QRM/QRN to chase something rare. This is piped to a PACTOR box a couple of versions back (new ones are way too expensive for my occasional need), and owns an AT-140 tuner and Shakespeare 393 vertical antenna pushing against part of the rail as a counterpoise. Even though it’s not mounted in the panel yet, I’ve been using this lately on 20 meters with good results.
  • ic-706Icom 706mk2G – a classic mobile, which also does multimode on VHF and UHF as well as HF… this rig I have had for many years, and think of it as a reliable backup. Ages ago, it was part of my mobile lab during speaking tours, and kept me amused during long drives. My original plan here was to wrap it in foil and pack it in a Pelican box for emergencies, but why not just build it in and add the potential for cross-banding or easy access when something fails… not to mention monitoring multiple things at the same time?
  • ft-817Yaesu FT-817 – the little QRP (5-watt) rig I bought about 10 years ago when working on the backpack technomadic toolset (here is the drawing). This is a much-loved little thing, and likewise ventures into the VHF and UHF bands… I expect to use it mostly for WSPR and other digital modes where processing gain can make up for low power; if it ends up living on one high HF band, it will probably own a thin wire dipole.
  • id-5100aIcom ID-5100 – finally, this is the most recent acquisition… a D-Star dual-band mobile with touchscreen remote head. With some reluctance, I sold my Kenwood TM-D710 to Steve Stroh N8GNJ to justify this purchase. By doing so, I gave up APRS and the data port, as this is the best 9600 data radio currently available off the shelf (thanks to the integrated TNC)… but I gained access to an Internet-linked network of gateways and reflectors. Damn trade-offs. I’m still getting to know the new rig, and have not decided yet if that was a mistake. Default antenna is a dual-band Rocky Mountain J-Pole, but this is via the coax patch panel so it can be swapped around if I need to use the Arrow beam or other tool.

APRS with Yaesu 290I might also need a 220 rig to engage with a geeky subset of northwest hams, but I’m out of console space and that would probably be tucked back in a corner. I’m also very tempted to devote my trusty old Yaesu 290 to embedded APRS. I’ve had this in my truck for about ten years, and it uses a stalwart old Kantronics TNC along with a Garmin GPS to transmit my location to other hams or the online tracking servers. In practice, I almost never use this while driving anymore, but it would be fun on the boat and easy to include. I also have the companion 790, which would pair well with another TNC for back-door control via handheld.

All this offers overlapping but differing capabilities, and the architecture of the audio networking system and independent antennas will allow simultaneous operation (whether with multiple people, or one human plus a few automated processes). For safety, their native audio outputs connect to a single dumb rotary switch in the middle of the cluster, allowing any to drive the single console speaker if all that fancy stuff has gone belly-up… or I just want to do the retro thing and not bring up computers as potent as yesteryear’s Cray to throw a few switches and twiddle knobs. It’s a sickness, I know.

weld-mount-tuner-at140Some of the antennas are up. The most recent installation was the AT-140 tuner for the M802 rig, mounted with the wonderful Weld Mount fasteners and 8040 adhesive to the hull. This pushes a 23-foot Shakespeare 393 mounted to port with the 409 kit, near the stern. There is an art to making a decent HF counterpoise on a fiberglass boat, and folks use sintered stainless under the waterline, clusters of wires cut for multiple bands, connections to tankage or engines, copper straps to thru-hulls, or… in my case… the stainless rail around the boat (safety issues duly noted, with testing required). Initial trials have only used the short segment from the port-side gate aft, but I’ve been doing well on 20 meters even with recent geomagnetic storms making propagation disappointing. I’ll go into much more detail about this and the other antennas in a future post.


Meanwhile, for keeping my ear to the ground, the delightful Uniden Home Patrol 2 is working well with its DPD OmniX antenna… a skyhook I was happy to find, as it doesn’t scream “scanner!” as does a discone. I had my heart set on the BCD-536HP for maximum feature set and DIN standard mounting, but my friend Steve bought the 436 and found the UI annoying enough to return it… and that convinced me to get this far more friendly rig. You can see at a glance what it’s doing, and management via Sentinel on the Windows box <shudder> was actually not as horrific as I imagined… once I got past the challenging evening of using the registry editor, installing an old version of .NET framework, Googling for hints in forums, and other things typical of a newbie stumbling into a well-established culture in which nobody even notices the absurd complexities any more.

With that, I’m going to pause before diving into the ever deeper pool of related material… there has been lots of other progress and the backlog of blog topics is getting scary (though I micro-blog on Facebook). It’s time to get out of back-screeching chair-slouching computer mode and do some more hardware!

Cheers and 73 de N4RVE aboard Datawake… hope to catch you on the air.


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Datawake Historical Photos – Circa 1976

Vic Franck Delta 50 (The Chief) in her early years

One of the little treasures I found aboard the boat now known as Datawake was a binder of photos from her youth. I think these are from the late 1970s (she was built in 1974), and they are quite a contrast from my usual view of the ship… a huge blinking console full of electronics. But much is unchanged, and these are a treasured part of the boat’s history. All images are clickable for larger versions… they are faded prints on yellowed paper, but if you peer hard enough you can get a sense of her finish and construction quality. One of these days, when things are “done,” I’ll take photos from the same perspectives and pair them with each of these; in the meantime, you can see more current images in my “Meet Datawake article from 6 months ago.


chief-binder-2 chief-binder-3 chief-binder-4 chief-binder-5 chief-binder-6 chief-binder-7 chief-binder-8 chief-binder-9 chief-binder-10 chief-binder-11 chief-binder-12 chief-binder-lines zooming

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Popeye and the Dawg

Witnessing an inter-species encounter

photo ©2016 by Steven K. Roberts
(All rights reserved – please contact for usage info)

Every now and then, a photographer gets lucky… the right palette of colors, a self-organizing composition, and a sweet vignette all align at the moment of shutter-release. This was one of those, caught through the 83X zoom of the wonderful Nikon P900, looking sternward from Datawake

That’s Popeye the harbor seal, a local celebrity, meeting a lovely dog who was strolling the docks with visiting humans at the Port of Friday Harbor. I first posted this on the local “Rant ‘n Rave” group, whence it has been shared about 75 times. I’m probably anthropomorphizing, but it is just so damn… adorable.


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Rebecca Parks and her Under Pressure series

My dear friend Rebecca moved to Missouri last year, and in addition to her many family activities and house-renovation projects, she is exploring a new artistic realm. When she posted this image of her latest porch-mildew work, I was inspired to write a bit of ArtSpeak to help solidify this emerging genre.

Under Pressure – an Exploration of Meta-Patterns


2016 photo by BJJ

With her “Under Pressure” series, Rebecca Parks expands Outsider Art onto the virgin landscape of the rural deck, exploring the dialectic contrast between Relaxation Spaces and the technologically mediated high-velocity streams of water with which she creates thoughtful, mandala-like representations of family dynamics, overwhelming information, and transitory states. Often pausing in reflection, her own moisture merging with that of a yet-unfinished work, the artist steps into the canvas of macro and micro to remind us of scale, giving a high-five to the hyphae while drawing attention to the vast gulf between the ambient humidity in which mildew thrives and the explosive intensity of the blast that sweeps it away.

Rebecca thus explores the very extremes of water, from passive to invasive, turning these into metaphors of each other and by extension, of information and power. The viewer becomes participant, invited to contemplate our own narrow range of survival and the transition from informational stasis to the overwhelming flood that destroys some and nourishes others, leaving an indelible yet transient meta-pattern on the landscape of our culture. In her representation of this, Parks has captured the diverse cultural overlay of the Internet, our own assimilation, and the struggle that belies the beguiling passivity of a rural porch bathed in the informationally rich vapors of WiFi.

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Building a Feline Outhouse

Take it Outside, Kitty…

by Steven K. Roberts, aboard Datawake

Isabelle and Steve aboard DatawakeOK, so I admit it… I love this cat. Isabelle lives aboard with me, and her tubby cuddly awesomeness increases the quality of life in lots of ways. But even a quirky Russian Blue who pushes all the right feline buttons but lives indoors comes with one little “feature” that can’t be avoided: the need for a cat box.

For the first four months aboard, this was located in the shower compartment of the guest cabin, where I figured it could have its own vent window and be mostly out of sight. But when a friend stayed aboard for few days, we had to relocate Izzy’s facilities to the afterdeck, leave the door propped open, and keep the canvas zipped shut… and that residual smell in the forward head never did go away. This is too much of a lifestyle impact in a limited space, and besides, I have more guests on the calendar.

catbox furnitureIt occurred to me that what she really needs is an outhouse on the afterdeck, with private entrance, exterior ventilation, easy access for cleaning, LED lighting, air filtration, and of course a network camera so I can see if it needs attention. And while we’re at it, might as well make it useful as bench seating for humans. This article is about the resulting project, which has solved the problem… and I share it here for others with big boats, small houses, or other spaces where a contained exterior cat box is needed.

I should mention that my first approach was to simply buy such a thing… surely this problem has already been solved! Indeed, I did find a few enclosed cat facilities on Amazon. But MDF/composite construction in a marine environment turned me off to one that had negative reviews for getting damaged by the inevitable wet spills, and another that looks like a large planter pot would have been cute but a pain to interface with a door in a vertical wall.

Still lazy, and not wanting to sacrifice a tempting antique linen chest that nearly went under the knife, I ordered a wooden toybox that was marginally big enough. I’m not going grace it with a link here… it was awful, with manufacturing errors that made it impossible to assemble, and it was too wimpy anyway. Everything on a boat must handle dynamic human weight. Back to Amazon it went.

OK, fine. I guess I have to build something.

catbox assemblyThe dimensions were non-critical… large enough for a nice big litter box or maybe a fancy self-cleaning one down the road, with enough additional room for a jumbo cat door and a few extras like vents and a small air purifier. I settled on 40 inches long, 20″ deep, and 20″ tall… with a simple hinged lid. I used 3/4″ ply for the bottom and top, with 1/2″ for the sides. I’m no woodworker, so there is nothing at all fancy here… just some scrap 2×4 ripped in half to give me a way to fixture the big pieces, with 1×2 verticals inside all four corners. At reasonable intervals, I used stainless wood screws to provide clamping pressure, with white glue smeared on all mating surfaces.

I screwed 8 rubber feet to the bottom to allow air flow, and ended up removing the front row of four and adding a spacer strip to compensate for the greater-than-90º angle between wall and floor (this is a boat, so by definition nothing is square).

hinge closeThe top surface needed to be smooth for piling stuff on (like cushions) so I decided to cut recesses for the hinges. This involved the router and some clamped-on wood scraps as a guide, with bit depth set to match the thickness of surface-mount polyolefin hinges that I had in stock from a previous unfinished project. These happened to have ideal dimensions, with the holes spanning the 3/4″ lid after recessing, and the thickness served as spacers for exactly the gap I wanted between box and wall.

(If you’re following along with the idea of cloning this, none of the dimensions are critical, as long as it’s big enough for the box at one end with room for the door to swing at the other.)

catbox handleThere are a few other details. I wanted a handle on the lid… so found a scrap of 1″ webbing and an old piece of kayak paddle shafting, then attached it with two screws. Not shown (and unnecessary once installed, but nice during construction) is a stainless wire with eyes, screwed to inside top and left side to keep the lid from flopping all the way open and breaking something.

right-ventFor ventilation, I installed a large plastic grille near the bottom in the front (visible in the photo above with cushions), along with a smaller one high on the right side. Convection brings clean air in, across the litter box, then out… and so far that seems to be working if we are not in windy conditions that make their own rules. The door has a felt seal, so smell rarely makes it inside.

catbox hole under deskOf course, the hardest part is cutting a hole in the boat. We skippers have a reluctance to do that, even above waterline, and this was to be a big one…. a “Tubby Kat” door (to Isabelle’s utter mortification) with a 7.5″ x 10.5″ flap. This not only required the saber saw for cuts on box and wall, but the trusty Fein tool to remove a section of that structure that supported the sofa back when this boat was optimized for human comfort. While hacking away under the desk, I added two holes for 3/8″ carriage bolts to keep the plastic door from carrying stresses, along with a larger one (using a hole saw) for that thru-hull fitting that I use to pass wiring. This carries Ethernet, camera power, 12V for the LED, and 115VAC for the air cleaner.

Adding the door and other hardware (after a couple of casual clear coats with water-based polyurethane), here was the first look at the box installed…

catbox door

But wait, that’s too dark! Isabelle needs to see clearly to do a good covering job, and I need to see clearly when cleaning it. And besides, there’s the webcam to consider. I installed an LED license plate light that cost about $5 from Super Bright LEDs… with a 12V pair running around to a 1-amp output on Shacktopus. The light is mounted on the back, above the box, and the camera is on the left (still without the air cleaner shelf or motion and lid sensors). Just this side of the camera mount are hooks for the cleaning shovel and a little brush/dustpan to tidy up… and I will add a mat to help with clean feet on the way back into the cabin.

complete with camera

By this point in the project, I had already let her alpha-test the box for a few days without having to push through a door, but now it was time to get serious. From the human side, a forbidding gateway presented itself, and she sniffed around it a few times without interest.

catbox door cabled

I carried her outside and poured her in, then returned to my desk to call her. Somewhat pathetically, she pawed the door. “Steev. Why Izzie in jail?? Free me nao?” Her reluctance to use it persisted over the next day, but she got over it and it’s now just an accepted part of the on-board facilities.

catbox-camOn the tech side, I still haven’t added the sensors for door and lid, though it’s not really an urgent problem compared to the long list of other projects aboard. What was immediately essential, however, was bringing the camera online… which is a trivial task since I have a gigabit switch for the on-board LAN a few feet away. With a quick power cable splice and two RJ-45 connectors crimped to some CAT-5 cable, my old Axis 210 was back in service.

Now I can keep track Izzy’s comings and goings, so to speak, and know when cleaning is necessary without all those tedious steps of shuffling out back and lifting the lid. It’s one click from the home screen of the Datawake web interface.

And, back to the initial point of all this, I got my guest cabin back! Here’s the “other” business end of the system, with the air cleaner and odor filter installed (that is resting on a couple of old shelf brackets, with 4″ Velcro strips on back and end to keep it stable):



I posted a link to this article on Facebook, and added a brief photographic narrative of Isabelle’s reaction to the presence of the webcam:

When I first told her about the camera idea, she said, "oh, jeeze..."

When I first told her about the camera idea, she said, “oh, jeeze…”

"Hang on... the webcam doesn't have an open port in the firewall, does it Steev? I just followed that CAT-5 cable..."

“Hang on… the webcam doesn’t have an open port in the firewall, does it Steev? I just followed that CAT-5 cable…”

I'm so busted. She's doing a press conference right now about the webcam...

I’m so busted. She’s doing a press conference right now about the webcam…

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The Datawake ADS-B PiAware Receiver

Tracking Aircraft with a Raspberry Pi

by Steven K. Roberts

One of my obsessions over the years has been collecting data, probing the radio spectrum, sensing outside my normal limited visual and hearing range, and deploying probes to expand my awareness of the environment. This leads to recognition of patterns, better understanding of how things work, and the almost voyeuristic thrill of peeking behind the curtains of technology or human activity.

Most of the machines I’ve built share this as a common thread, with radio receivers, cameras, and sensors all contributing to “situation awareness.” Aboard Datawake, there is a suite of communication tools that include four SDR (software-defined-radio) systems along with a cluster of amateur radio gear and other receivers in the console. This article is about the first of those to be brought online… the ADS-B ground station that collects location data from aircraft and contributes it to FlightAware. Why? Because we can.


This was mostly a packaging project; I didn’t have to invent anything, other than a way to keep the hardware tidy, cool, and reliably connected to my network. Since there is quite a lot of interest in doing exactly this, I thought I’d share the details.

ADS-B Feeder Basics

AIS-Valis-screenshotThis is similar in many ways to AIS, which is of course much more relevant to my nautical needs… in fact, I used to run Marine Traffic Station 401 here on San Juan Island (which moved to a friend’s house when I vacated my old lab building). In the marine environment, that provides extremely useful information about nearby boats, sometimes as an overlay on the chart plotter, seeing around corners (unlike radar) and giving a heads-up about potential collision situations. It is also the basis for a whole mini-industry of live ship tracking, with Marine Traffic just one of many services. This operates on 162 MHz, and is increasingly used by recreational boaters.

In the flying world, there is a similar tool called ADS-B (an acronym for the chewy “Automatic Dependent Surveillance – Broadcast”). This operates on 1090 MHz, and is so far mostly on commercial aircraft. Like AIS, it provides radar-like functionality by having individual planes determine their own position via GPS, then share it by broadcasting packets that can be received by other aircraft or ground stations. I am now one of the latter, in turn feeding that data to FlightAware, which is one of the commercial services that let folks track planes as they make their way between airports.

The most cost-effective way to do this is with a dedicated Raspberry Pi running PiAware copied into a micro-SD card, along with a receiver dongle, 1090 MHz filter, and ADS-B antenna. In my case, there is also a POE splitter to allow the rig to run via power over Ethernet off my Netgear switch, eliminating an additional messy cable and wall wart. Here’s the rig, as a temporary lash-up before packaging:


Assembling the Station

There are a few issues affecting my packaging choices:

  1. Although the three colorful main components (filter, receiver, and Pi) easily attach together as a rigid assembly, the loads from heavy antenna cable and mounting could be high enough to stress connectors. I chose to connect the filter and receiver directly to minimize insertion losses, but use a USB extension cable from there to the computer.
  2. The exposed Raspberry Pi would be subject to static damage from a casual touch, so it needs a case (and besides, I didn’t have any small hardware on the boat to simply park it on stand-offs).
  3. The POE splitter is on the right, and needs no special attention other than appropriate cable routing for Ethernet in and out, as well as power to the Pi.
  4. I worried a bit about excessive heat gain when first considering sealed packaging up on the bridge deck. Research on this subject was inconclusive, with reports of overtemp errors in hot attics, so I elected to put it into a clean environment below and optimize the layout for convective airflow. Besides, blinkies.

adsb-pi-case-printingThe first job was to package the Pi, and since I have a Lulzbot Mini 3D Printer aboard I went to Thingiverse and found a nice sleeve case. I used Cura to slice the STL file and make a 4.3 MB gcode file, sent that down to the OctoPi attached to the printer, told it to start, and went to bed. In the morning I had this lovely thing (I tossed the little end cap):


This was printed with HIPS (High Impact Polystyrene), which is not my favorite material… but it’s forgiving and works fine for things that don’t have to flex or be terribly precise. The Pi slipped into this with some reluctance, exposing the micro-SD slot, micro-USB for power, HDMI and audio (unused), Ethernet, and the four USB ports.

pi-case-velcroFor the overall substrate, I grabbed a black plastic electronic enclosure I had lying around; this is the kind with bottom surface, top cover attached with four screws into threaded bosses, and front and back panels. The latter were not used, as I wanted maximum convective airflow from vertical mounting on the wall, and in that spirit I mounted the Pi case with the slots upright and unblocked by Velcro. None of this is terribly critical, it turns out; temperature measurement with a Fluke IR thermometer is showing 93º F on the Pi board at the moment with ambient at a comfortable 76° F (this is unscientific; I haven’t figured out how to see reported CPU temperature via FlightAware or the local server).

With this done, it was a simple matter to lay out the hardware in the generous space of my 8×9-inch enclosure. The Pi box is Velcro’d on, and the other items are zip-tied via holes drilled as needed. Because of the different thickness of the filter and the receiver (from center SMA-connector axis to bottom surface), I glued a 1/4″ pad of Neoprene underneath the receiver to minimize connector stress when pulled down by the zip ties. Here’s the whole machine, ready to mount in the boat:


Placement of this on the wall was dictated by the antenna cable, which is 7 feet of LMR-400 routed down through the bridgedeck console and through the corner of the pilothouse. It is stiff and needs wide easy curves, and that pretty well defined the orientation and position of the box. I slapped on two industrial strength Velcro strips and it was done, with a nice coax curve into the filter and the Ethernet cable to the splitter. The open ends are at top and bottom, so convective airflow should be enough to keep the Pi happy (and if not, it will be easy to add a fan).


The ADS-B Antenna

There are lots of ways to do this part, and as a true hobbyist I probably should have taken the time to build any of the homebrew designs that can be found online. But for $45 I could be lazy, and just get the project done… I bought one of the 1090 MHz antennas produced by FlightAware on Amazon.

Cable loss is the biggest issue at these frequencies (well, other than antenna placement), so I minimized the length by going with the 7-foot option. This ended up being a tighter constraint than I had planned, and with the stiff LMR-400 cable, sharp bends were not an option. The solution was to mount it on the inside surface of the wall around the upper helm station, using stand-offs and long 1/4″ bolts to let the antenna clear the rail structure:


adsb-antenna-baseThe connector is the N-type, and I gave that a little extra protection with some self-fusing silicone Rescue Tape (great stuff to have around). This whole lashup, including the final curve into the unit down in the galley, needed every bit of that 7 feet of cable, but better that than a big loop of lossy excess as so often happens. The mounting left four ugly bolt ends and nuts on the outside of the boat, and that’s annoying enough that I’ll either make a cover or find a way to use it for another purpose. But it did manage to span the edge of the canvas that covers the wrap-around smoked windshield, eliminating the need to do any fabric hacking… and initial results indicate that the location is fine despite an orthogonal aluminum strip on the top edge of that covered acrylic surface.


Comparing my “feeder” performance to other stations serving ADS-B data to FlightAware, it looks like this is working beautifully… with plenty of hits over 200 miles. It’s fun to click on individual planes, go explore their tracks, and correlate that with what I see in the sky or hear on the local Friday Harbor Unicom or more distant ATC channels.


You can see my statistics at FlightAware here. Before actually getting this beast off the dock, of course, I’ll have to deal with either auto-updating my own location or simply taking it offline to avoid confusing MLAT and stats-generation. That won’t be an issue for a while yet…

warm-adsb-glowAs I admitted at the beginning, this is all rather irrelevant to the obvious nautical mission of Datawake, but it contributes to the larger mission of more deeply understanding the world around me. It’s fun, too. But all that aside, I hope the construction tips in this article are helpful to others who wish to add ADS-B feeder capability in more conventional settings, packaging the hardware in a way that will keep it running for a long time.

I’ll close with a short video snippet of the Pi case printing on the Lulzbot Mini down in the boat’s machine shop…

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Lotus Blossoms

Every now and then, the pixels align, the light is right, and the subject is perfect. This post has nothing to do with geeky boats, technomadics, blinky gizmology, communication tools, or even Isabelle the cat… it’s just a photo I took at a friend’s garden pond in Friday Harbor on June 18. It’s worth viewing at full size (click the image).

Double Lotus in Friday Harbor
©2016 by Steven K. Roberts

Double Lotus - Steven K Roberts

This was done with the Samsung S6 at maximum resolution, with a minor crop and addition of the credit. Makes me want to buy this…

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The Roberts Law of Fractal To-Do List Complexity

One of my “Roberts Laws” about project management, recently meme’d with nice graphics by Dave Hickey. Thought I should immortalize it here in the archives….


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