How to Set Up an Android Tablet for Use in the Field for Burst Digital RF Communications, Part One: Initial Setup, by 4nt1p4tt3rn

I’m going to walk you through the steps necessary to securely configure an Android tablet for field use, so you can take advantage of andFLmsg to send burst digital RF comms over an inexpensive radio such as the Baofeng UV-5R.

Part of this was removed from the original. Here is the reason

Here is the OPs explanation:

ALCON: I’m not positive yet, but those $40 tablets I’m using for the tactical tablet/digital burst RF comms guide…they might have an issue with the final input stage on the headphone jack. Specifically, if you over-drive them, you might blow the input, effectively neutering the tablet’s ability to hear audio on the line. Just be aware, and set your audio levels accordingly. For now, I do not recommend cranking your radio to full volume when transmitting or receiving. I’d say half, at best. I need to do some more testing, tho. In the meantime, https://walmart.com/ip/onn-7-Tablet-16GB-Storage-2GB-RAM-Android-11-Go-2GHz-Quad-Core-Processor-LCD-Display/800435260 is a great alternative, and is known-good in this application.

I apologize in advance if this is, in fact, the case. A poorly-designed input stage was not on my list of corners that might be cut on a budget tablet like this; I truly hadn’t forseen that as an issue.

While these instructions will work for pretty much any recent tablet or phone (though I very, very strongly recommend against using a phone in the field, due to signals security (SIGSEC) considerations), this guide will be specific to this tablet, running Android 11. We will not be modifying the OS or flashing a new one, because this tablet will never be associated with any account, nor will any apps on it. Neither will it ever be connected to any network.

Let’s start with unboxing the tablet. This is the box for it:

Opening the box and removing the tablet, you can see it’s already in its protective case:

Step 1: Disconnecting the speaker and microphone

While our primary app for digital burst RF comms uses audio to do its job, disconnecting the speaker and mic will have no negative impact on its functionality, as the speaker and mic functions are wired to the headphone jack separately.

Why are we doing this? Simple: I’m assuming you’d rather not catch multiple rounds because, in your haste to send a report back to base, you accidentally pressed the “volume up” button on the side of the unit and the thing made a loud noise a few hundred meters from the enemy.

There are three major concerns with using a device like this in the field:

1. Signals discipline (controlling your RF emissions)
2. Light discipline (controlling your light emissions)
3. Sound discipline (controlling your sound emissions)

We’ve just permanently (but reversibly) ensured that sound discipline isn’t a concern for you. We’ll address the other two as we progress through this tutorial.

How do we know where the speaker and microphone are? Look at the bottom edge of the tablet. You should see something similar to this:

The multiple holes on the left edge are indicative of a speaker, and I also verified this by having the tablet play sounds. The single hole on the right is indicative of a microphone element. Once the rear cover is removed, you can also visually identify the microphone while looking at the exposed; it’s the small, round, silver element in that corner.

You will also able to positively identify the speaker and mic connectors by reading the printing on the main circuit board.

If you look to the right of the left connector, and to the left of the right connector, you’ll see “SPKR” and “MIC” printed on the board, indicating the purpose of the two connectors.

Let’s remove the protective film on the screen and remove the tablet from the case. We’re doing this because we’re going to be opening the tablet’s shell up, along the seam on the back, seen here:

Using a spudger or plastic pry tool from a kit such as this one: https://www.amazon.com/iFixit-Prying-Opening-Tool-Assortment/dp/B0762BVXDY/, or even just an old guitar pick, we’ll be prying the back of the shell off. A great place to start is the seam just below the USB C charging port, seen on the right nearest the camera in the photo above. I find it easiest to start here. Once you have your pry tool inserted, just begin twisting, and the snap nearest your tool should pop open. Slowly work your way around the right edge, prying and twisting, popping the case open bit by bit. Soon, you should have worked your way to the bottom, and pried that up as well. By now, you should be able to get your fingers under the cover and pull it the rest of the way off.

Once you’ve done this, you should be able to see the internal circuitry of the tablet:

In this photo, I’m using the edge of one of my pocketknives to hold the nonconductive tape back that was covering the surface-mount technology (SMT) connector on the left – the small off-white block you see in the photo. There’s a matching one at the base of the blade on the right.

These two wires connect the speaker (left) and microphone (right) to the main circuit board. Using your fingernails, a knife, or a dike or needlenose pliers, gently pull the smaller block with the wires downward towards the bottom of the tablet, and the connector should disengage itself from the larger block. Do this for the other connector as well, and it should look a little like this:

We could also disconnect the camera, but it may come in handy, so we’ll leave it connected for now. Likewise, we’ll leave the wifi and Bluetooth antennas connected, because they will be necessary for one of the apps we’ll be installing later.

Now, put the back cover back on by snapping it back into place. The proper orientation should be obvious, because there’s a portal for the camera lens in the upper left.

Step 2: Initial operating system (OS) setup

Hold the power button in to power on the tablet. Once on, you should see a screen similar to this:

Once it’s finished booting, you’ll see this screen. Go ahead and click the “START” button, assuming the language setting is as you want it:

Next, it’ll want to connect to wifi, and identify nearby wifi networks. Not today, Satan! Click “Set up offline” in the lower left on this screen:

Now you’ll be taken to some basic Google Services configuration. Be absolutely sure you disable everything on this. Don’t forget to scroll, because there’s more offscreen. Once everything is disabled, hit “Accept”:

Next you’ll be prompted to set a screen lock PIN. You can, or you can choose not to. There are good arguments to be made for either choice. Personally, I do not intend to be storing anything compromising or otherwise damaging on this device. Further, should the device be captured, a 4-digit PIN on a lock screen isn’t going to stop anyone even remotely capable. To me, having to enter the PIN is just wasted time. So I hit “Skip”. You, however, do you:

Congratulations! You’ve made it through the initial setup. You should now be at the main interface, which should look like this:

Step 3: Post-setup configuration

Now that we’ve got the tablet to a basic level of functionality, let’s start tweaking the settings to make sense. Open the Android Settings app by clicking on the gear icon in the lower right corner of the screen. You should see a menu that looks like this:

First, go into “Network & Internet” and ensure WiFi is off. Thanks to the way we’re doing this, Bluetooth is also off, even though it’s not shown here. If you want, you can verify this from the top pull-down menu.

Next, to assist in managing light discipline, go into “Display” and enable Dark theme:

For those of you not using this specific tablet, you may see an automatic brightness level setting. If it’s present, disable it. You do not want your brightness suddenly maxing out when you’re trying to maintain concealment at night, even if you are taking measures to conceal any light emissions.

In the “Sounds” menu, I minimize the Alarm and Notification volumes, and disable all “Other sounds and vibrations”. I don’t want the thing vibrating, and I don’t want to risk an errant alarm or notification sound playing in the middle of a data burst.

In the “System” menu, select “Date & time”, ensure that “use network provided time” is disabled, and then manually set the date and time by clicking on each and setting them:

Finally, in the “Location” menu, under “Advanced”, ensure everything’s off, particularly Emergency Location Service:

Tomorrow, we will go over side loading apps to the device and radio preparations.