How to Fix Virtual Router Plus Could not be Started Error

There can be different reasons for the Virtual Router Plus Could not be Started Error. Three methods to troubleshoot this issue are discussed below. Try these methods one at a time in the order 1 to 3, till your problem is solved. Hope these work for you

Method 1

1. Right-click network, click properties, change adapter settings, disable WiFi adapter by right clicking it and selecting disable from the context menu. Not the one created by Virtual router Plus.
2. Once disabled right click on it again to enable it.
3. Now try connecting to internet.

Method 2 

1. Press Windows key + X, select Command prompt (Admin)
2. Then type the following:
   netsh wlan set hostednetwork mode=allow ssid=VirtualRouter key=123456789
3. Enter
4. Then type :
   netsh wlan start hostednetwork
5. Then try connecting to internet.

Method 3

1. Open Network and Sharing Center->Change adapter settings. Alternatively you may right-click network, click properties, change adapter settings
2. Right click the adapter you use to connect to the internet (Ethernet/WiFi/Data Card) and open its properties window.
3. Now go to the sharing tab and enable the 'Allow other network users to connect.....' and select the Home networking connection 'Ethernet/WiFi' as shown in the figure
4. Click OK
5. Now disable and then enable this adapter.
6. Now try connecting to internet.

Antenna Array

An antenna array is a configuration of multiple antennas (elements) arranged to achieve a given radiation pattern. A single-element antenna is usually not enough to achieve technical needs. That happens because its performance is limited. The set of discrete elements, which constitute an antenna array, offers the solution to the transmission and/or reception of electromagnetic energy. The geometry and the type of elements characterize an antenna array. Antenna array factor quantifies the effect of combining radiating elements in an array without the element specific radiation pattern taken into account. The overall radiation pattern of an array is determined by this array factor combined with the radiation pattern of the antenna element. The overall radiation pattern results in a certain directivity and thus gain linked through the efficiency with the directivity. Directivity and gain are equal if the efficiency is 100%.

Classification
The phasing of the uniform linear array elements may be chosen such that the main lobe of the array pattern lies along the array axis (end-fire array) or normal to the array axis (broadside array).

Broad side array
Broad side array is the arrangement of identical antennas, which are placed along the axis perpendicular to the direction of maximum radiation. The identical antennas are equally spaced along the line of axis and all the elements are fed with equal magnitude of current with the same phase. This results in array pattern known as broad side array. It is evident that broad side array is bidirectional where maximum radiation is obtained in the direction of axis perpendicular to the array axis. By placing an identical array at a distance of λ/4 behind the array, bidirectional array can be converted to unidirectional array and by lead current in phase by λ/2.

End Fire Array
An End fire array looks similar to broad side array except that the individual elements are fed with the current that is equal in magnitude but opposite in phase. In other words, the individual elements are excited in such a way that a progressive phase difference between adjacent elements becomes equal to the spacing between the antennas (elements). “The arranging of identical antennas along a line drawn perpendicular to their respective axis so that the principle direction of radiation coincides with the direction of the axis of array” is known as End fire array. The radiation is maximum in the direction along the axis of the array i.e., 0 degree (or) 180 degree. If two equal radiators are operated in phase quadrature at a distance of λ/4 apart, an end fire couplet is said to be formed.

Rare Earth Doped Fiber

Most popular solid-state gain media are the rare-earth-doped laser crystals and glasses. These media are doped with rare earth ions – most commonly trivalent and rarely divalent ions (in special laser devices). The rare earth ions replace other ions of similar size and same valence in the host medium. For example, an Nd3+ ion in Nd:YAG (yttrium aluminum garnet) substitutes an yttrium (Y3+) ion.

Table: Common laser-active rare earth ions and host media and important emission wavelengths.

ION	COMMON HOST MEDIA	IMPORTANT EMISSION WAVELENGTHS
neodymium (Nd3+)	YAG, YVO4, YLF, silica	1.03–1.1 μm, 0.9–0.95 μm, 1.32–1.35 μm
ytterbium (Yb3+)	YAG, tungstates, silica	1.0–1.1 μm
erbium (Er3+)	YAG, silica	1.5–1.6 μm, 2.7 μm, 0.55 μm
thulium (Tm3+)	YAG, silica, fluoride glasses	1.7–2.1 μm, 1.45–1.53 μm, 0.48 μm, 0.8 μm
holmium (Ho3+)	YAG, YLF, silica	2.1 μm, 2.8–2.9 μm
praseodymium (Pr3+)	silica, fluoride glasses	1.3 μm, 0.635 μm, 0.6 μm, 0.52 μm, 0.49 μm
cerium (Ce3+)	YLF, LiCAF, LiLuF, LiSAF, and similar fluorides	0.28–0.33 μm

Active fibers not only guide light, but also provide laser amplification. In these fibers, some amount of rare earth ions is incorporated into the fiber. The steps involved in active fiber amplification are:

	1	The pump light, typically at a shorter wavelength than the signal to be transmitted, is injected into the fiber.
	2	The laser-active ions absorb the pump light and get excited into some metastable states.
	3	The excited ions can now amplify signal light via stimulated emission.

Figure: Energy level structure of the trivalent erbium ion, and some common optical transitions.

Wide range of methods exist for the active optical fiber fabrication. The fabrication methods broadly classified as:

	1	Preform-based methods which is the most important method for the production of glass fibers
	2	Direct fiber production methods which is the oldest fabrication technique. It is less suitable for producing ultra-pure fibers with very low losses. This is because it is difficult to avoid any contamination with material from the crucible. This method is commonly used for fabrication of plastic optical fibers. An example is fabrication based on extrusion

Important Atmospheric Layers for Electromagnetic Waves

The ionosphere is a region of Earth's upper atmosphere, from about 60 km (37 mi) to 1,000 km (620 mi) altitude, and includes the thermosphere and parts of the mesosphere and exosphere. It is ionized by solar radiation, plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. The various layers of the ionosphere are listed below:

D-Layer
Height        : 70 Km
Thickness   : 10 Km
Disappears at night
Aid: Very low frequency & LF Waves.

E-Layer
Height       : 100 Km
Thickness : 25 Km
Disappears at night – due to the recombination of ions.
Aid: Medium frequency

ES – Layer
Sporadic E-Layer

F1-Layer
Height : 180 Km
Thickness : 20 Km
Combines with F2-layer at night.

F2-Layer
Most important layer.
Height: 300 Km – 400 Km (will come down to 250 Km at night)
Combines with F1-layer at night
Persist at night.
Low density of air layer because there is no collision between electrons.
During sun spot the deflection decreases.

[Image IonosphereLayers-NPS.gif: Naval Postgraduate School derivative work: Phirosiberia (IonosphereLayers-NPS.gif) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons]

What is MIMO

Multiple-Input Multiple-Output (MIMO) technology is a wireless technology that uses multiple transmitters and receivers to transfer more data at the same time. Wireless products with 802.11n support MIMO. This is part of the technology that allows 802.11n to reach much higher speeds than products without 802.11n.

MIMO technology takes advantage of a radio-wave phenomenon called multipath where transmitted information bounces of walls, ceilings, and other objects, reaching the receiving antenna multiple times via different angles and at slightly different times. Multipath is a natural occurrence for all radio sources. Radio signals bounce of objects and move at different speeds towards the receiver. In the past multipath caused interference and slowed down wireless signals. MIMO takes advantage of multipath to combine the information from multiple signals improving both speed and data integrity.

MIMO technology leverages multi path behavior by the use of multiple, smart transmitters and receivers with an added spatial dimension to dramatically increase performance and range. MIMO allows multiple antennas to send and receive multiple spatial streams at the same time. Smart transmitters and receivers are used with all 802.11n devices. Using multiple antennas the data can be sent and received through multiple signals. More antennas usually equates to higher speeds. A wireless adapter with 3 antennas may have a speed of 600 Mbps while an adapter with 2 antennas has a speed of 300mbps. The router also needs to have multiple antennas and fully support all of the features of 802.11n to gain the highest speed possible With this extra bandwidth cannot be needed for achieving high data rate.

MIMO makes antennas work smarter by enabling them to combine data streams arriving from different paths and at different times to effectively increase receiver signal-capturing power. Smart antennas use spatial diversity technology, which puts surplus antennas to good use. If there are more antennas than spatial streams, the additional antennas can add receiver diversity and increase range. In order to implement MIMO, either the station (mobile device) or the access point (AP) need to support MIMO. Optimal performance and range can only be obtained when both the station and the AP support MIMO. Legacy wireless devices can't take advantage of multipath because they use a Single Input, Single Output (SISO) technology. Systems that use SISO can only send or receive a single spatial stream at one time.

How to calculate the value of a ceramic capacitor

You might have come across situations were you needed to calculate the value of a ceramic capacitor. Today a large variety of such capacitors are available in the market but the value calculation of all remains the same. All these capacitors are marked with a three digit number code, say, 104. There are two key points to remember in the value calculation. First point is that in the marked number code the first two digits are the significant digits and the third digit is the multiplier. The second point is that the final value is in the 'pico Farad' unit (without conversion).

For example, a value 104 on the capacitor indicates that the value of the capacitor is 10 x 10⁴ pF or 100 nano Farads (μF) or 0.1 micro Farads (μF). Some other codes and their corresponding values are given below:

Capacitor Code	Value in pF	Value in μF
101	100	0.0001
102	1000	0.001
103	10000	0.01
104	100000	0.1
105	1000000	1

For some capacitors there will be an additional alphabet code at the end of the number marking say 104J. This alphabet code indicates the capacitor tolerance. The tolerance values are calculated as given in the table below

Code	Tolerance
C	±0.25pF
J	±5%
K	±10%
M	±20%
D	±0.5pF
Z	+80% / -20%

For example, 104J coded capacitor has the value 0.1 ± 5% μF. 
For a 104C coded capacitor, the value is 0.1 μF ± 0.25pF