Category Archives: Tech Devices

How to Completely Remove a Book from Your Kindle Device


You have a book in your Kindle application (in your iPhone). You want to completely remove it.


1. Press and hold the book title and remove the book from your device (e.g. your iPhone).

2. Login your Amazon account.

3. Search for the Manage Your Content and Devices link.

4. Go to Manage Your Content and Devices.

5. Select Books or Docs beside the Show label.

6. Select the book and click Delete button.

7. On your device (e.g. your iPhone) scroll down to refresh your Kindle books.

How to increase your Wi-Fi connection speed


You have a slow Wi-Fi connection speed.

You want to increase your Wi-Fi connection speed.


Execute below command on Windows:

netsh wlan show interface
  • If your Signal is less than 20% then try to increase your Wi-Fi signal strength by moving your device closer to your Wi-Fi router.
  • If you cannot change your device and Wi-Fi router location then try connecting your Wi-Fi router to another Wi-Fi router (Wi-Fi extender) that acts as a new access point using LAN cable.
  • If you cannot use a LAN cable then try connecting your router to a Wi-Fi repeater that is closer to your device.
  • If your Radio type is 802.11n then try to upgrade both your device and router to support 802.11ac.
  • Try to upgrade your Wi-Fi router to support 5 GHz band.
  • Try to upgrade your Wi-Fi router to support MU-MIMO (which stands for Multi-User, Muliple Input, Multiple Output).
  • Compare Receive rate (Mbps) and Transmit rate (Mbps) before and after making a change.
  • Use Speedtest to compare your Wi-Fi connection speed before and after making a change.

How to Fix the Dell Laptop “Hard Drive Not Installed” issue


Suddenly, when turning your Dell laptop on you get the error message “Hard drive Not installed” and cannot boot into Windows.

  1. Power your laptop and quickly press F2 key to enter BIOS.
  2. Expand System Configuration node.
  3. Click SATA Operation.
  4. Select AHCI option.
  5. Click Apply button.
  6. Click Exit button.
  7. If the problem still persists then restore BIOS settings to Default BIOS settings and try the procedure again.


How to change language of an EPUB file

Problem: Sometimes you have an EPUB file encoded with a wrong language tag.
Therefore when you use the Read aloud feature of the Google Play Books application the book is read aloud in a wrong language.


  1. Download the EPUB file to a PC.
  2. Change the extension from EPUB to ZIP.
  3. Open the .ZIP file.
  4. Open the content.opf file using the Notepad app.
  5. If you cannot file this content.opf file then please navigate to the OEBPS folder.
  6. Find the tag <dc:language> and change its value (e.g. from <dc:language>en</dc:language>to <dc:language>vi</dc:language>).
  7. If you cannot find the tag <dc:language> then just add a new tag right above the </metadata> tag (e.g.
  8. Save the content.opf file and rezip the EPUB file.
  9. Change the file extension from ZIP to EPUB.

How to transfer Photos from iPhone to PC with highest quality

Problem: Images copied directly from iPhone to a PC usually have lower quality in comparison with the original quality due to format conversion.

You want to preserve the quality as high as possible.


  1. Connect iPhone to a MacBook.
  2. Open Photos app.
  3. Click on iPhone’s name under Devices section on the left.
  4. Select photos on the right.
  5. Select Import to = Library or New Album.
  6. Click on Import N Selected button, where N is the number of selected photos, to Import photos from iPhone to iPhotos.
    • The imported photos will be copied from iPhone to iPhotos.
    • You have to manually delete the photos directly from iPhone if you want to permanently remove them from iPhone.
  7. Click on an album name on the left menu in iPhotos.
  8. Select the imported images in the album.
  9. Click File > Export > Export N Photos… (N is a number) to export photos from iPhotos to a folder on MacBook.
    • Select Arrow icon at the end of Photo Kind
    • Select PNG
    • Select Color Profile = Original
    • Select Size = Full Size
    • Select Movie Quality = 4K
  10. Click the Export button.
  11. Enter a folder name.
  12. Click the Export button. Wait for the exporting process to be completed by reviewing the circle icon in the toolbar.
  13. Share the folder in a LAN.
  14. Copy the folder to a PC.


1080i vs. 1080p: What’s the Difference?

Most TVs today have two modes with similar names: 1080i and 1080p. Both have the same screen resolution, so what’s the difference between the two? Which one should you choose?

1080i video is “interlaced.” 1080i video plays back at 60 frames per second, but that’s a bit deceptive, because it’s actually broadcast at 30 frames per second. The TV then displays those frames twice, in a way—the first pass is 1,920-by-540 for the even scan line field, and the second pass is 1,920-by-540 for the odd scan line field. The process by which this occurs is called interlacing. It contributes to a sense of motion and reduces perceived flicker.

1080p video is called “progressive scan.” In this format, 1,920-by-1,080-pixel high-definition movies are progressively drawn line after line, so they’re not interlaced. On paper, that may not seem like a huge deal. But in the real world, what you end up seeing looks sharper and more defined than 1080i, particularly during scenes with a lot of fast motion.

Sometimes 1080p is termed “full HD” or “true HD,” to distinguish it from 1080i or 720p video. Blu-ray discs contain 1080p video at 24 frames per second, and then, using a method known as 3:2 pulldown, display it at 30 frames per second on screen.

Both formats look similar on smaller TVs. As a general rule, you need a larger TV to notice the difference between 1080i and 1080p. Depending on your eyesight, you can probably pick up the difference on a 32-inch LCD if you’re particular about it. But most consumers don’t really see a marked difference until at least a 42-inch screen, if not larger.

1080p isn’t even the best anymore. Technology never stands still, of course. High definition meant 1080p (1,920 by 1,080) resolution for years, but it’s quickly being overtaken by ultra high definition television, commonly called 4K.

A UHD or 4K display is one with at least 8 million active pixels. For televisions, that resolution has standardized to 3,840 by 2,160. Digital cinema 4K (the resolution in 4K movie theaters) is slightly higher at 4,096 by 2,160. However you define it, it’s four times the number of pixels on a 1080p display, and over 23 times the resolution of standard definition television.

If you don’t have a 4K source video, a 4K TV can still make your movies and shows look better. All 4K televisions use some kind of upconverter to display 1080p and lower resolution video. These upconverters do more than just break each pixel into four identical pixels; they employ edge smoothing and noise reduction algorithms to produce, ideally, a sharper picture. When it works well, you get video that looks natural on a 4K screen (though it doesn’t add any actual new details, just sharper lines and more even color and light). When it doesn’t, the picture can look a bit blotchy, like a painting.

While regular viewers struggled to see the difference between 1080p and 720p on smaller televisions, it’s much more obvious on 50-inch and larger TVs. 4K is another significant jump in terms of clarity and detail, especially as people are becoming more and more used to the incredibly tiny pixels displayed by today’s high-resolution screens on mobile gadgets.

Source: PCMag.



Resolution vs. Pixel Density in Displays


Which display should you choose when buying a TV or laptop or mobile device, bigger size or bigger resolution?


Size Display size is measured in inches. Here we only measure the diagonal size in inches and not the horizontal or vertical size of the screen.

Square the horizontal or vertical size of the screen in inches, and add the two numbers together. Find the root of that resulting number, and you have your display's diagonal in inches.

Pixel It is the smallest element that can be displayed on a screen. To be more simple, it is just a single dot on a display or a screen.

Resolution Resolution refers to size of the display in terms of pixels. E.g. Resolution of 800×600 pixels means that the there are 800 pixels horizontally and 600 pixels vertically. So therefore there are a total of 480000 pixel in the display.

Square the display's width and height in pixels, and add the two numbers together. Find the root of that resulting number, and you have your display's diagonal resolution in pixels.

Pixel Density Many of us are not aware of the importance of Pixel Density in displays. It is the thing which describes the sharpness and clarity.

Pixel Density is usually measured in PPI (Pixels Per Inch) which refers to number of pixels present per inch on the display. Higher the pixel density higher is the sharpness of the content.

Pixel Density is calculated based on the resolution and size of the display.

Pixel Density = Diagonal resolution in pixels/Diagonal in inches

Consider the above image. The alphabet “A” on the left is displayed on screen (32 inch display size) with lower resolution. The alphabet “A” on the right is displayed on the screen (32 inch display size) with higher resolution which delivers better sharpness.

What does this mean?

The thing with PPI is that with the same resolution, the larger the screen, the lower the PPI, the lower sharpness. This is because a larger screen means the individual pixels have to be larger to fill the space.

If you compare iPhone 6s Plus and Samsung Galaxy S7 Edge which both have the same size 5.5 inch but iPhone 6s Plus comes with 1920×1080 resolution at 401 PPI while Galaxy S7 Edge comes with  a 2560×1440-pixel resolution at 534 PPI. It means the text and images on the Galaxy S7 Edge’s display are sharper than on the iPhone 6s Plus’ display.

The interesting thing about devices that boast a higher PPI that 400 is that your eyes can’t see the high concentration of pixels at normal smartphone viewing distances. Your naked eye can only see densities of up to 399, so you won’t be able to tell the difference between a device with a PPI of 400 and 440 (the Samsung Galaxy S7 Edge, for example).

Some examples:

  • Dell XPS 13 (2016) has a pixel density of 276.
  • Dell Precision 5510 Workstation 15 (2016) has a pixel density of 282.
  • MacBook Pro 13-inch (2016) has a pixel density of 227.
  • MacBook Pro 15-inch (2016) has a pixel density of 220.

How to Transfer Files and Music to an Android Phone Using USB

So you’ve plugged your USB to microUSB cable into your computer and Android phone and are ready to start downloading files.

Staring intently at your screen, you wait for a drive, a window — something, anything — where you can drag-and-drop your files, but it just doesn’t come.

Well, chances are, you are missing one simple yet critical but step.

Here’s how to transfer files to your Android phone:

  1. Connect your Android phone to your computer using the microUSB to USB cable.
  2. If you are using a PC, you will see an installation bubble pop up in the bottom right of your screen. Wait for the computer to successfully complete installation.
  3. The critical step: On your Android phone, pull down the notification window (aka ‘window shade’) and tap USB connected.
  4. A notification window will appear. Tap Mount. Your phone will enter USB storage mode.
  5. Find the removable storage drive. On a PC, navigate to My Computer and look for a new removable storage drive. On a Mac, the drive will appear on your desktop.
  6. Drag-and-drop the desired file(s) to the drive.
  7. In your phone’s notification window, tap Turn off USB storage.
  8. Unplug your phone and you’re all set.


Wireless Basic Configuration

Mbps vs. MBps: What’s the Difference?

Mbps means megabits per second. Mb is used for download and upload speed.
MBps stands for megabytes per second. MB is used for file size.
130Mbps = 16.25MBps
144Mbps = 18MBps

Differences between 802.11a, 802.11b, 802.11g and 802.11n

Operates in the 5.15GHz to 5.35GHz radio spectrum.
Speed: Up to 54Mbps (actual throughput is closer to 22Mbps)
Range: 50 feet
Less prone to interference.
More expensive.
Because 802.11b and 802.11a use different radio technologies and portions of the spectrum, they are incompatible with one another.

Operates in the 2.4GHz radio spectrum.
Speed: Up to 11Mbps
Range: 100 feet
Prone to interference (it shares airspace with cell phones, Bluetooth, security radios, and other devices).
Least expensive wireless LAN specification.

Operates in the 2.4GHz radio spectrum.
Speed: Up to 54Mbps
Range: 100 feet
Prone to interference (it shares airspace with cell phones, Bluetooth, security radios, and other devices).

Operates in the 2.4 or 5GHz radio spectrum
Speed: Up to 700Mbs
Range: 50 feet

802.11ac builds upon previous 802.11 standards, particularly the 802.11n standard, to deliver data rates of 433Mbps per spatial stream, or 1.3Gbps in a three-antenna (three stream) design.
The 802.11ac specification operates only in the 5 GHz frequency range and features support for wider channels (80MHz and 160MHz) and beamforming capabilities by default to help achieve its higher wireless speeds.

Don’t Mix Wireless B/G with N

Wireless N is supposed to be interoperable with Wireless A, B, and G, but it doesn’t always work that way. Some older clients might not be able to connect at all, even when the wireless router or APs are in mixed wireless mode. Then when the older clients can connect, they’ll slow down the network.

Some clients may take a heavy 80 percent cut in their throughput. To prevent this problem, consider forcing the new APs to use only Wireless N, and keep the old router or APs around to support the old clients.

Although connections among users on the Wireless N router or APs with Wireless G users will still be bottlenecked by the old clients, the throughput cuts on a mixed mode Wireless N router or AP can be much worse.

Change your wireless channel

Changing your wireless channel might help increase range and performance, especially if you have neighboring networks set on the same channel or interference from other electronics. It’s best to check channel usage with a program like Vistumbler or inSSIDer, but you can simply try other channels as well to see which one is best.

For 2.4GHz routers (the most common), channel 6 is the default for most routers, so stay away from it. Try channel 1 or 11, the other two other non-overlapping channels. For 5GHz wireless N or AC routers, you shouldn’t have much of an interference issue since it’s less commonly used. But you might try changing to another channel as well.

Use WPA2 security

For the high speeds on wireless N or AC routers you must use WPA2 security with AES encryption. Using WPA or WEP security with TKIP encryption will dramatically reduce bandwidth. Most routers offer a mixed WPA/WPA2 mode, but you should use WPA2 only. Homes should use the personal (PSK) mode, which is the easiest to setup and businesses should use the enterprise (RADIUS) mode which requires an external authentication server.

Most devices you have should support WPA2 security, but if you have some that don’t consider using an older router with a newer one as mention in the previous section.

Short Guard Interval

The guard interval is the space between symbols (characters) being transmitted.  This is often confused with the space between packets, which is the interframe space (IFS).  The guard interval is there to eliminate intersymbol interference, which is referred to as ISI.  ISI happens when echos or reflections from one symbol interfere with another.  Adding time between symbol transmission allows these echos and reflections to settle in before the next symbol is transmitted.  In normal 802.11 operation, the guard interval is 800 ns.

With 802.11n, short guard intervals are possible.   The short guard interval time is 400ns, or half of what it used to be.  Shorter wait time (guard interval) between symbols increases throughput.  However, if it’s too short, the amount of ISI will increase, and throughput will decrease.  On the other hand, if the guard interval is too long, there is increased overhead due to the additional idle time.

If you are using 802.11n or 802.11ac only, you can enable short GI. In another word, when using mixed mode, please disable the short GI, which may cause issues.
When intending to improve the throughput, enable short GI can improve the throughput about 10%.

RTS/CTS Threshold

As an optional feature, the 802.11 standard includes the RTS/CTS (Request to Send/Clear to Send) function to control station access to the medium.
For access points, you enable RTS/CTS by setting a specific packet size threshold (0 — 2347 bytes) in the user configuration interface.
If the packet that the access point is transmitting is larger than the threshold, it will initiate the RTS/CTS function.
If the packet size is equal to or less than the threshold, the access point will not kick off RTS/CTS.
Most vendors recommend using a threshold of around 500.
The use of 2347 bytes effectively disables RTS/CTS for the access point.


Difference Between Core i3 and i5 and i7 and Core 2 Duo

Generally speaking the current generation of Core i3/i5/i7 have about 20% more processing power than their Core 2 Duo counterparts.

Core i3:
– Dual Core CPU
– Hyper Threading

Core i5:
– Dual Core CPU
– Slightly higher clock speeds than core i3
– Hyper Threading
– Turbo Boost (it’s like an automatic overclock if the CPU is not too hot)

Core i7:
– Dual Core CPU (models ending with M)
– Quad Core CPU (models ending with QM)
– Higher clock-speed than the Core i5
– Hyper Threading
– Turbo Boost
– Virtualization (you can run multiple operating systems at the same time)
– Has circuitry that allows for easier and more secure remote access for corporate IT departments to trouble issues in a business environment.
– AE5 New Instruction set (No idea what this is)