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Review of Winbook TW700 Tablet

This may be the smallest, cheapest device that will run standard off-the-shelf Windows software, including amateur radio APRS mapping software.

The Winbook TW700 is a 7" Windows 8.1 tablet computer.  "Winbook" is the house brand of MicroCenter, a small computer store chain with about 20-odd stores and a website at http://microcenter.com .

Microcenter once offered this device at the unbelievable price of USD $60 new, and $47.95 for "open box" units; i.e. customer returns.  The Winbook is no longer in production, but it and similar Windows 8.1 tablets often turn up at radio swapmeets.

The new and open-box prices shown on the website fluctuated constantly, apparently linked to the stock market, the current weather, the phase of the moon or some combination thereof (???).  On a visit to the Madison Heights, Michigan store on 7 June 2015, new units were selling for $69.95 (had been 79.95 a week earlier), open-box units in a box were $55.95, and bare units with no box and no charger were selling for 47.96.

For an inexpensive piece of hardware, this device has an amazing number of features:

Despite the CPU being a quad-core 64-bit device, the installed version of Windows 8.1 is the 32-bit flavor.

(This is part of Microsoft's desperate attempt to counter the Android tablet market, and to recover from the debacle that is Windows 8.  Microsoft has traditionally charged a royalty of $30-$50/unit for each copy of Windows installed on a new computer.  This is a complete non-starter for products retailing for $100 or less. By contrast, the Android OS is free to manufacturers.  MS is now offering a bare-bones minimum 32-bit version of Win 8.1 to manufacturers at NO CHARGE, ala Android, if the tablet device has less than a 10" screen. MS hopes to kick-start the market for Windows "app" development and the Microsoft Online Store.

Actually the 32-bit OS is not as big a liability as it might seem.  The main advantage of the 64-bit version is the ability to utilize more than 4GB of RAM. Since the machine has a mere non-expandable 1GB of RAM, 64 vs 32-bits is a non-issue. The main issue that arises is that this machine boots from a 32-bit UEFI bios; a highly non-standard configuration.  This causes problems for bootable (from CD or flash drive) third-party backup and troubleshooting utilities that assume all UEFI loaders are 64-bit.)

The device weighs about 350g (12.3 oz) and is about 18.9 x 12.1 x 1.1 cm (7.5 x 4.75 x .45 inches). The internal 3000mA lithium battery is charged & powered through the micro-USB port.  A 5V 2.1A high-current wall charger similar to the ones used by iPads is provided with the TW700. In another similarity to "i-Gadgets", the device is completely sealed - the battery is not removable.


IMPORTANT TO NOTE:     This unit uses the "bastardized" Apple interpretation of the USB standard.  The official standard of the USB working group defines that USB 2.0 ports on computers shall be capable of providing a max of 0.5 amps at 5 VDC to an attached device.   Smaller devices like cellphones, scanners, digicams, external hard disks, USB hubs, LED mini-lamps, etc live within this limitation, and can run and/or charge from a standard USB port on a desktop PC.

When Apple discovered that they simply couldn't get the current drain of the upcoming iPad down to only 500mA, they unilaterally redefined the USB standard to provide 2 amps instead.   They introduced the "over-sized" 2.1-amp USB wall charger along with the iPad.  (Note that the iPAD's charger is about twice the size physically of the iPHONE's although the styling and packaging are similar.  The iPhone lives within the "legal" USB standard of 500mA max drain.) 

Only these oversized chargers (both from Apple and third parties) will properly run and/or charge an iPad or the TW700.  No port on a PC or normal USB hub can supply enough current to do this. This forces you into the tradeoff of :   Connect to PC port for USB data exchange but no charging --OR-- connect to oversize USB wall charger for power/charging but no data exchange.      Pay close attention to third party AC and DC "USB chargers".  If the charger doesn't EXPLICITLY say 2.1 amps, it is only a "legal" 500mA device and won't run or charge an iPad or other tablets.    Commonly on dual-port  12 VDC cigarette-lighter-jack USB chargers, one port will be a standard 500mA port for a cellphone, while the other (usually color-coded differently) will be a 2.1A port for a tablet.

I suspect that a lot of the open-box returns of the TW700 to Microcenter were by people that naively assumed all USB ports are the same, and that they could charge and run this device by plugging it into a PC's USB port, just like their cellphone.    Because the PC USB port simply CAN'T supply enough current, the device's battery would gradually run down and "die", prompting a return.  (There is a surprising amount of customer feedback on various sites to the effect of "it worked great for a day and then died.")   Oh well, it just benefits us by providing a supply of dirt cheap "open-box" devices that really don't have anything wrong with them!


I did some power drain tests using a "Kill-A-Watt" AC voltmeter/ammeter/wattmeter and a "Watts Up" DC voltmeter/ammeter/wattmeter.  I had the tablet running UIview + Precision Mapping + the UZ7HO Soundmodem "soft TNC", with the display set at full brightness for these tests.

On AC power using the provided 5V 2.1A wall charger, the KIll-A-Watt AC wattmeter indicated about 7.5 watts at initial power-up up including a slight inrush to the internal battery.   After a 15-minute wait for the battery to top off at full charge, the AC drain dropped, to about  6 watts.  Obviously this will be no pain at all to a Field Day generator setup.

For the DC power test, I used a generic two-USB-port 2.1 amp "iPad charger" that plugs into a lighter jack (a.k.a. "12VDC power outlet" in newer cars) acquired for USD $10.95 at a Pilot truck stop. The "Watts Up" DC meter indicated 12.6 VDC from my shack battery plant during these tests.

[The large chain truck stops a.k.a. "travel centers" such as Pilot, Flying J and Love's are actually a very useful source for all manner of 12 VDC gadgets including inverters & chargers, power connectors, heavy-gauge red/black DC zip cord, 12 VDC fans, 12 VDC TV/DVD players, and even microwave ovens & mini-fridges that run on 12 VDC. Not to mention the wide assortment of coax jumpers, antenna mounts, SWR meters, external speakers, RF connectors and adapters, etc targeted at the trucker CB trade but also useful for hams. Driving a VW Jetta TDI diesel, I tend to stop at these places fairly regularly...]

At this extremely reduced brightness the display is nearly unreadable (except perhaps after "lights out" on a campout) but all program processes are still running at full speed.   Since Windows Power Management allows the display to be dimmed to a low level normally, and then brighten up when keyboard, mouse or screen taps are sensed, this could still be a practical minimum-standby-power mode for a messaging terminal or an unattended APRS digipeater or igate. 

With the display set at 50% brightness and running the UIview suite (UIview 2.03, Precision Mapping 9.0,the PMap 9 Server, and the UZ7HO Soundmodem sound card "soft TNC" ) continuously, the run time on a fully-charged battery was about 4 hours. At an indicated 5% charge (as displayed by the Windows Power Status indicator in the system tray), the unit went into a complete power-off shutdown (not a low-power "sleep", "standby" or "suspend"  mode).   


The unit has a 4-conductor "TRRS" 3.5mm combined headphone & mic jack. It is pinned-out identically to the ones on iPhones and iPads. This means any boom-mic headset made for i-Gadgets will work with this unit - think EchoLink operation. More importantly, it means the homebrew soundcard interface I made for my iPad works as-is with the TW700.

Having mic-in (radio receive) and speaker/headphones-out (radio transmit) combined on a single 4-contact jack can be inconvenient for sound-card interface hookups since these devices typically expect separate jacks for computer audio-in and audio-out.   This inexpensive splitter cable, available from CableMart, will convert the tablet's single audio jack to the customary separate speaker and mic jacks.

Note that there are TWO standards for the pin-out of the 4-conductor TRRS jack: The older standard was used for combined stereo audio and composite NTSC video out on analog camcorders and related equipment.  The other is the standard introduced by Apple for headsets with mics on iGadgets, which as also been adopted by many other tablets and netbook PCs.  Any cable you use with the TW-700's mic/speaker jack must explicitly say compatible with Apple devices.


Two very similar tablets are also available from MicroCenter.  The TW801 gives you a larger 8" screen and a USB 3.0 port, but appears to be otherwise identical.  The TW802 is identical to the TW801, but with 32GB of SSD instead of 16GB.

Ports from left to right:  Microphone Hole, Micro-HDMI, Micro-SD-Card, 3.5mm Audio In/Out Jack, Full-size USB, Micro-USB

Out of the box, the TW700 runs a more-or-less standard version of Windows 8.1; i.e. not the RT "pseudo-Windows".  I installed the freeware "Classic Shell" utility to do away with the Win 8 tiled smart phone user interface (a.k.a. "Metro" a.k.a. "Modern").  I now have a traditional XP/Win 7-looking user interface with a fully-functional Start Button, Start Menu and the ability to have more than one program running on screen.

Contrary to the report on one or two websites, there is NO GPS receiver built into this unit. It DOES have the "Microsoft Location Service", a system resource that is part of the standard Windows 8 load.    IF you are connected to the Internet, this built-in function can determine your location, based on your current IP address, surprisingly accurately, and plot it on the provided "Bing Maps" app.   Location Server DOES NOT seem to offer any emulation of a serial port carrying NMEA that would be useful with APRS programs.

The machine has a 16 GB SSD (solid-state drive), of which only 8 GB is visible. The other half is a hidden partition containing a complete install/restore image of Windows 8.1 .    In an ingenious adaptation to the limited drive space (compared to a normal desktop hard disk), Windows boots and runs directly from a compressed "WIM" (Windows IMage) file in the hidden restore partition. (This is unlike conventional PCs that do a complete Windows install on the visible drive C from a hidden file or partition during the initial first-time-run setup.)

Only the Windows registry, user settings, some minor utilities and temp-swap-hibernate files are located on the visible C: partition.  A "restore" merely deletes the user settings and user-installed software on drive C. Due to the hidden image file being used for every boot (not just restores) it CAN'T be deleted to free up disk space.  Note that this device uses the severely locked-down Windows 8 UEFI boot process making it very difficult to replace the installed OS with another, or to clone the disk setup with a bootable flash-drive-based backup utility.   This device literally is a miniature Windows 8 PC.  If you plug an external keyboard into the USB port and hit "F2" repeatedly during power-up, it will jump into a "BIOS" (excuse me - UEFI) setup screen just like a "real" PC.

Perhaps, due to the tiny size of the solid-state disk drive, the machine was blessedly free of the usual collection of "crapware" unsolicited pre-loaded junk software.  After removing the trial version of Microsoft Office 365" (a rent-by-the-month version of Microsoft's office suite), 5.6 GB of the machine's SSD was free.  

Within a day, about a gigabyte of the free space had disappeared. The moment this device connects to the Internet, Windows Update automatic downloads begin trickling in and filling up the empty drive space.  (Windows Update not only replaces existing files with updated versions, it stores spare copies of each update installer on your local drive in case Windows Repair needs to re-install them. This bloat is even larger than it would appear, since each individual patch or update includes a self-executing installer that is often larger than what is being installed.)  This starts eating up gigabytes of disk space.  

Assuming this device is not going to be used for casual or promiscuous web browsing, but rather primarily for off-line applications like ham software, radio programming utilities, automotive OBD reader programs, etc  DISABLE Windows Update to stop this disk-space-consuming flood of patches. Go to "Control Panel, Windows Update" and switch the settings from "Automatically Download And Install Updates" to "Notify Only" or even "Never Check For Updates".  (Note the even if disabled, you can always trigger a Windows Update scan and offer of files to download manually.)

You can free up another approximately 2 GB of space by downloading and running the "WinBookOptimize" utility available here


on the Microcenter website.  This utility deletes the Windows OEM "hibernate" file, and reduces the size of the 
pagefile.sys  system swap file.

There have been scattered reports that this utility contains a malware trojan. This is most likely a false positive due to the compressed self-extracting EXE file this utility is provided in.  (While these "packer" utilities are themselves legitimate, they are are also widely used for distributing self-installing malware.)      If you are uncomfortable downloading and running the optimize utility, you can achieve the same results yourself manually.

All the utility does is reduce the size of the Windows swap file, and deletes the Windows hibernation file.    

BACKGROUND: The hibernate file is used to capture a snapshot of the state of all RAM when you power-off the machine.  The next time you power-on, RAM is almost instantly reloaded from "hiberfil.sys" exactly where you left off, with the same programs already open and running.  This avoids the ponderous and lengthy traditional cold-booting process.  It also allows the system to automatically save it's current state, including open user files,  just before the battery expires.   Since the hibernate file is a snapshot of the contents of all the RAM on the system, it will always be about the same size as the amount of installed RAM.  I.e. on this system around 1GB. 

By deleting the hibernate file, you recover 1GB of disk space at the expense of much longer boot times.

You can make these changes yourself, without the automated "WBOptimize" utility.

To resize the swap file: 

  • Go to "Control Panel, System" and click the "Advanced System Settings" on the left side of the screen.
  • On the resulting  screen, click the "Advanced" tab and then the "Settings" button in the "Performance" box.
  • On the next screen, click "Advanced" (again!) and then the "Change" button in the Virtual Memory box.
  • Edit the maximum size down to 1024 MB.
  • Click the "Set" button and then "OK" your way out of this cascade of boxes.

To delete the Hibernate file:
  • Open a command prompt, a.k.a. "DOS Box" in administrator mode; i.e. locate "Command Prompt" under "Administrative Tools". RIGHT-click this entry and choose "Run as Administrator".
  • At the prompt in the black box, type this line and hit <ENTER>
         powercfg /h off  
    (Obviously a command for "Powerconfiguration" with an option switch for hibernate file, and argument to disable.)

You can free up about another half GB of disk space by eliminating the ability to roll back currently-installed updates.  Once again, go to the command prompt a.k.a. "DOS Box" in administrator mode.  Enter the following command line and press <Enter>:

     dism.exe /online /Cleanup-Image /StartComponentCleanup /ResetBase 


Running Windows 8 with 1GB of RAM and a hard disk with a mere 5.6 GB free may seem a hopeless undertaking, but the machine boots about as fast as a typical PC and is reasonably responsive loading and running programs. Perhaps this is due to the system drive being a flash drive instead of a traditional spinning-platter mechanical hard disk.  You will not be using this machine to run large games, Photoshop, video transcoders, AutoCAD or other power-hogging multi-gigabyte programs.  But it can easily run many lightweight legacy ham programs and small utilities.

As I had expected, trying to operate normal Windows GUI features and menus on such a diminutive touch screen was nearly impossible for normal human-sized fingers.  You will ABSOLUTELY POSITIVELY want a mouse of some sort.  One of the issues that bit me almost immediately was the inability to easily do the equivalent of mouse RIGHT-clicks with a finger on the touch screen.  (The UIview "alternate mouse movements" heavily depend on right-clicks.)  I would recommend a Bluetooth cordless mouse that can link to the TW-700's built-in Bluetooth functions.   This avoids wasting the valuable single USB port for the receiver dongle of the typical non-Bluetooth cordless (or USB corded) mouse.

NOTE: One CAN do a right-mouse click with a finger on the touch screen, by touching and holding your finger in place for a second or two until the right-click context menu appears, but this is slow and awkward. And doing a right double-click (which UIview uses) is still impossible.

(The inability to manipulate standard menu-driven Windows mouse-and-keyboard-based programs, with fingers instead of a mouse, on a small screen is one of the key reasons why small Windows tablets have been a complete failure in the marketplace. And why this little device is now being sold so incredibly cheaply!)

While you are at it, you might want to get a complete Bluetooth keyboard/mouse combo.   The tablet's virtual "glass keyboard" that pops up on-screen ala iPhone or iPad is very minimal.  It lacks PC function keys, and more critically the "PgUp" and "PgDn" keys (used to zoom in and out in many mapping programs including UIview) are missing.

An alternative is to NOT USE the tablet-style "glass keyboard" provided as part of the Windows 8.1 tablet-oriented interface.

Instead, use the standard "On-screen Keyboard" that has been part of Windows for handicap access, since Windows XP, instead. It DOES have the missing virtual keys, including function keys, PgUp, PgDn, Caps, etc.  Further, the case of the letters displayed on the virtual keytops actually changes to give a clear indication of caps lock state. 

Assuming you have installed the "Classic Shell" and have a normal WinXP/Win7-style desktop and Start Menu,  go to the "Windows Ease Of Access" Start Menu group and launch "On Screen" keyboard.  You may want right-click this item and choose "Pin To Taskbar" to make this virtual keyboard accessible directly from the Task Bar in the future.  This keyboard has another advantage over the default tablet "glass keyboard": It can be repositioned anywhere on the screen by dragging it's title bar, just like any other Windows window. You can drag most of it off the left side of the screen so that just the critical "PgUp" and "PgDn" keys are visible. Note that you must click or tap on the title bar of the window behind the floating keyboard (i.e. the one that you are trying to type into) to shift system focus, before the keys will have any effect.

A hardware alternative that provides a mouse substitute and a full keyboard with PgUp and PgDn is this tiny Bluetooth keyboard/trackpad combo from Amazon: 
It works with i-Gadgets and Android devices as well (i.e. anything with Bluetooth linking capability).

Photo courtesy of Rick Lautenbach

While you wouldn't want to do major editing with the virtual keyboard or the mini hardware keyboard, it is surprisingly useable for pecking out one-liner APRS text messages, renaming files in the Windows Explorer, and filling in fields in options dialogs.

During the setups, I used the full-sized USB port to connect a mouse and keyboard on a USB hub.    I used the built-in WiFi-n to access another machine on my LAN, that hosts my software library, to do the program installs. After installing some essential minor system utilities, UIview 2.03, Precision Mapping 9.0, the PMap Server 9.0, NWS Shape Files, UI-HeightTrack, the UZ7HO Sound Modem, APRS Messenger, mmSSSTV and the FLdigi suite, I had about 1.1 GB of disk space left.

My TW700 is now effortlessly running a complete UIview 2.03 installation including Precision Mapping 9.0, the Precision Mapping 9 server and the UZ7HO Soundmodem soundcard "soft TNC".  With the soundcard DSP "soft TNC" running, the Win 8 Task Manager shows less than 25% CPU utilization and only about 2/3rds of the !GB RAM used.  (See screen shot below)

An alternative light-weight APRS setup for the TW700 would be the "YAAC" APRS client.   YAAC (which is a self-referential acronym that means "Yet Another APRS Client") uses Open Street Maps data, but stored locally. It is stored as vector data (rather than as thousands of bitmap tiled images) so it zooms in and out freely without pixelating (i.e. like Precision Mapping, MapPoint or Delorme Street Atlas). Because it is cached locally, YAAC can provide full mapping displays in the field without an Internet connection.  YAAC provides the AGWpe TNC interface, so the UZ7HO Soundmodem or DireWolf can be used as soundcard "soft TNCs".  Note that the YAAC application is written in Java, so you must install the latest Java Runtime for Windows first.

Details on interfacing the tablet's combination mic-in/audio-out jack to sound card interfaces is  here  on this website.

A screen shot of the TW700 running the UIview suite. This is an actual 2576x1932 pixel digicam snapshot of the TW700's 1280x800 pixel screen resampled back to approximately 1280x800 pixels. It is not a screen cap.  If you are viewing this pic on a screen larger than 7", this image is larger than life, but it is 1:1 pixels from the original screen.

By the way, if you want an external monitor for the tablet, look around for one of the now-passe 1440x900-pixel "WXGA" monitors that were common a few years ago, before full-HD 1920x1080 screens became universal.  The 1280x800 pixel screen of the tablet will not-quite-fill the classic 1400x900 screen. 1440x900 flat-panel monitors with LED back-light can now be had for under USD $100.00 for a 19" unit. Usually they had both analog 15-pin VGA connectors and DVI (Digital Video Interface) connectors.

A well-kept secret is that DVI uses exactly the same digital signal format as HDMI.  The only difference is the shape of the connector, and the fact that DVI does not carry audio connections like HDMI.  No signal-format conversion is required to connect HDMI video from the tablet into one of these older DVI monitors.  Only an inexpensive hardware adapter plug for an HDMI cable, like these under-$3.00 adapters from Monoprice.com, is required. Of course, you will also need a micro-HDMI-to-standard-size-HDMI cable. 

The lack of "PgUp" and "PgDn" keys on the virtual keyboard is a problem with the UIview Precision Mapping or PA7RHM map servers.  It is fairly easy to zoom inward for more detail by dragging out a bounding box with a finger on the touch screen, but there is NO easy way to zoom back out! The typical tablet two-finger "pinching" gesture has no effect on the UIview screens. I worked around this problem by temporarily connecting an external (physical) USB keyboard, zooming in and out with it's "PgUp" and "PgDn" keys to city, county, state and continental views.  I then saved each of these zoom levels with UIview's  "Map, Save A Favourite View" function.    You can then use "Map, Load A Favourite View" to zoom back OUT to one of these pre-stored views, after zooming IN with your finger.

Or alternately, use the Windows On-Screen keyboard described above. Unlike the default tablet "glass keyboard", the classic keyboard DOES have the critical "PgUp" and "PgDn" buttons.

The built-in front and rear cameras work quite nicely, even at relatively low light levels, offering real potential for live in-the-field SSTV operations using mmSSTV.  However, I am still trying to come up with an easy way to capture the camera images into files or clipboard caps I can load into mmSSTV for slow-scan TV transmission. 

No utility to activate the cams while on the classic desktop is provided.  (Except the factory-loaded copy of Skype.) The extremely light-weight "BooruCAM" webcam capture utility I have used for many years to framegrab webcam images for SSTV use doesn't want to work on Win 8. I am now searching for an alternate utility that will work, and that can trigger screen caps without function keys or mouse right-clicks so I can do this in-the-field with just the tablet.

You can get a camera pic into an SSTV program but it's somewhat clumsy. First, revert to the "tile-land" Metro interface by banging the right side of the window with your mouse or finger to reveal the Win8 "Charms" bar. Select "Start" which will send you to the Metro start screen. On the start screen there there is a Camera app tile that will take snapshots with either camera.  The camera app saves snapshots as .JPG files to a "Camera Roll"  ala iPhone or iPad.

Then switch back to the classic desktop and select the "TX" tab in mmSSTV.  Right-click (there you go again - need to be able to RIGHT-click easily!) in the TX picture window and choose "Load from file...".  Select  "My Pictures" and drill down to "Camera Roll" which shows as a sub-folder of \My Pictures .  Then double-click a picture to  select and load it.

Update:  You can place a shortcut to any of the Metro tile apps on the conventional Windows desktop, or "pin" the shortcut to the classic desktop Taskbar. I now launch the Camera app directly from the Classic Shell desktop's taskbar.  When you launch the Metro camera app from the classic desktop, and then close it after shooting the picture (by poking the upper-right corner of the full-screen camera app until the red-X close button appears), the Windows desktop automatically reappears.

Ideally, I would like to be able to activate the camera from the desktop, capture to the Windows Clipboard (not a file) ready for direct "Paste" into mmSSTV. The lightweight freeware BooruCAM utilty would do this in previous versions of Windows, complete with overlaying a line of previously-stored text (i.e. something like "WA8LMF SSTV LiveCAM") on the picture. Unfortunately, "BooruCam" doesn't want to play with the webcam driver in the TW-700.  (I suspect this is because BooruCam and similar utilities interact with cameras via the elderly Video For Windows (VFW) API, rather than the more modern Microsoft DirectShow video API.)

[The Black Cat Systems SSTV app for iPad is vastly superior and shows how this should be done. It calls the iPad cams directly from within the SSTV program and takes a snap instantly ready to transmit over SSTV.]

This tiny PC is a perfect match for the Kenwood TH-D72 APRS handheld.  With a standard USB-A to mini-USB-B cable connecting the D72 to the tablet's standard USB port, and the D72 providing an actual GPS, you have a complete fully-functional desktop-style mapping APRS setup with two-way messaging that can operate anywhere.

NOTE: You must have an EXTERNAL GPS connected to the TH-D72.  The D72 does NOT echo data from the internal GPS out the main data port when operating in the computer-connected "PACKET" mode. (There IS a kludge UIview initialization .CMD file for the TH-D72, that operates the radio in the "APRS" mode rather than "PACKET", that WILL allow the internal GPS to pass through to the computer.  However, you have to disable/enable various settings in the D72 menus manually each time you use it.)

With the tablet's audio in/out cabled directly to a Yaesu FT-818's 6-pin mini-DIN "data port", you would have the ultimate compact lightweight in-the-field HF PSK31/MFSK16/SSTV setup as well as two-meter packet/APRS capability.  [The FT-817/818/857/897 have a built-in "data VOX" function that eliminate the need for any soundcard interface PTT keying scheme - you only need the TX and RX audio connections to the mini-DIN port. The transmitter will key automatically when audio from the computer is sensed at the TX pin of the mini-DIN "data port". The "data VOX" function is completely separate from the normal voice VOX function, and is enabled by a separate menu entry.] 

You could then use the full-size USB port on the tablet for a $30 Globalsat BU-353 mini-hockeypuck GPS receiver. I have tested this combo and it works very well with MapPoint, Street Atlas or Precision Mapping as a substitute for a Garmin car navigator (though the Garmin's user interface is far more optimized for use on a small screen), and as a fully-functional APRS tracker/mapping/messaging terminal with UIview or YAAC.   The added power drain of the BU-353 reduces the battery run time of the tablet by about 30-45 minutes.  Of course, like a Garmin nuvi, you presumably would be using an external 12VDC charger.