Antenna Handbook

Learn 741 op-amp circuits basic with example

Transconductance Amplifier

This circuit is a voltage-to-current converter . Here's how it permits an input voltage to control the brightness

of an LED

R3 controls Vin , Vary R3 to alter Iout, hence the brightness of the LED.

Transimpedance Amplifier

Example : If R1 = 1000 Ohms then Gain = -1000

This circuit is a current -to-voltage converter. Here's how it transforms the current generated by a solar cell into an output voltage :

This circuit can amplify the signal from non-current generators like thermistors and photoresistors. connect one side of device to +9V and the other to pin 2 , ground pin 3.

Op Amp IC 741 Basics, Characteristics, Pins, Applications

The 741 is a highly popular general purpose OP-AMP. It is simple to use , reliable, and inexpensive, it is used in most circuits.

IC OP-AMP 741

741 PINS

IC 741 Pin Out

Maximum Ratings

Supply Voltage +/-18 Volt

Power Dissipation 500 mW

Differential Input Voltage +/-30 Volt

Input Voltage (note) +/- 15 Volt

Output Short Circuit Time Indefinite

Operating Temperature 0 Celcius to 70 Celcius Degree

Note : Input Voltage should not exceed supply voltage when supply voltage is less than +/- 15 Volts

741 Applications Circuit

Basic Inverting Amplifier Design

Basic Inverting Amplifier

Example : if R1 = 1000 Ohms and R2 = 10000 Ohms, then Gain is -(10000/1000) or -10.

This is one of the most common OP-AMP circuits. For A Non-Inverted output use the amplifier on the facing page.

example the application of basic inverting amplifier is Unity-Gain Inverter Circuit :

This circuit use as a buffer or to convert -Vout to +Vout

Non-Inverting Amplifier Design

Non-Inverting Amplifier

Example: If R1 = 1000 Ohms and R2=10000 Ohms, then Gain is 1 + (10000/1000) or 11

Note that Vout is an Amplified but not inverted version of Vin.

Example of Non-Inverting Amplifier application is Unity-Gain Follower circuit.

Use to buffer signal from another circuit

Quad Beam Loop Antenna Calculator

Cubical Quad Beam Loop Antenna is fullwave length Antenna, designed in the mid of 1940's , each side being a quarter wavelength, and fed at a current loop in the center of one side, the voltage loops occur in the middle of the adjacent sides — and that reduces or eliminates the arcing.

The background for the creation of the Cubic Quad Beam Antenna is due to the existence of shortwave radio stations located in the highlands. previously used a Yagi

antenna which is more suitable for lowland, to transmit worldwide with high voltage input, This antenna is fed in the middle of the current loop, so the end is the

high voltage loop. In the thin air of Quito, Ecuador,the high voltage at the tip causes a corona arc, and that arc periodically destroys the tip of the Yagi element.

so Design station engineer Clarence Moore designed Cubical Quad Beam antenna to solve this problem.

Fig 1. Quad Loop Antenna

Fig 2. Quad Loop Antenna

The antenna shown in Fig. 1 is actually a quad loop rather than a cubical quad. Two or more quad loops, only one of which needs to be fed by the coax, are used to make a cubical quad antenna. If only this one element is used, then the antenna will have a figure-8 azimuthal radiation pattern (similar to a dipole). The quad loop antenna is preferred by many people over a dipole for two reasons. First, the quad loop has a smaller "footprint" because it is only a quarter-wavelength on each side Fig 1. Second, the loop form makes it somewhat less susceptible to local electromagnetic interference (EMI).

The quad loop antenna (and the elements of a cubical quad beam) is mounted to spreaders connected to a square gusset plate. At one time, carpets were wrapped around

bamboo stalks, and those could be used for quad antennas. Those days are gone, however, and today it is necessary to buy fiberglass quad spreaders. A number of kits are advertised in the web.

The details for the gusset plate are shown in Fig.2 . The gusset plate is made of a strong insulating material such as fiberglass or in marine-grade plywood.

It is mounted to a support mast using two or three large U bolts (stainless steel to pre- vent corrosion). The spreaders are mounted to the gusset plate using somewhat smaller U bolts (again, use stainless steel U bolts to prevent corrosion damage)

Cubical Quad Beam Loop Antenna

The elements can be fed in the center of a horizontal side fig A, in the center of a vertical side fig B , or at the corner fig C

There is a running controversy regarding how the antenna compares with other beam antennas, particularly the Yagi. Some experts claim that the cubical quad has a gain

of about 1.5 to 2 dB higher than a Yagi (with a comparable boom length be- tween the two elements) . In addition, some experts claim that the quad has a lower angle of radiation. Most experts agree that the quad seems to work better at low heights above the earth's surface, but the differencdisappears at heights greater than a half-wavelength.

The quad can be used as either a single-element antenna or in the form of a beam. Figure Fig 3. shows a pair of elements spaced 0.13 to 0.22 wavelengths apart. One element is the driven element, and it is connected to the coaxial-cable feedline directly. The other element is a reflector, so it is a bit longer than the driven element. A tuning stub is used to adjust the reflector loop to resonance.

Because the wire is arranged into a square loop, one wavelength long, the actual length varies from the naturally resonant length by about 3 percent. The driven element is about 3 percent longer than the natural resonant point. The overall lengths of the wire elements are :

1. Driven element : L = 1005/F [MHZ] ft

2. Reflector : L = 1030/F [MHZ] ft

3. Director : L = 975/F [MHZ] ft

with Shortwave Frequency range : 3 - 30 MHz, Center Frequency F[MHZ] = 16.5 MHZ.

Quad Beam Cubical Antenna Calculator login form

Input Center Frequency (in MHz) for Quad Beam Loop Antenna

Quad Beam Loop Antenna Calculator

Input Center Frequency

Driven Element in ft
Reflector in ft
Director in ft

One method for the construction of the quad beam antenna is shown in Fig. 4. This particular scheme uses a 12 x 12-in wooden plate at the center, bamboo (or fiberglass) spreaders, and a wooden (or metal) boom. The construc- tion must be heavy-duty in order to survive wind loads. For this reason, it is probbly a better solution to buy a quad kit consisting of the spreaders and the center structural element.

The Common Base Amplifier

Common-base (CB) and common-gate (CG) amplifiers are the third form of single-transistor amplifier circuit topology. Their claim to fame is low input impedance, high voltage gain and high output resistance. This makes them a good choice for RF amplifiers.

The Common Base and Common Gate amplifiers are great wide-bandwidth amplifiers, with low input impedance and good voltage gain.

Example of Cesium JS application to display the movement of the iss satellite

Here is the JavaScript code:

<!DOCTYPE html>

<head>

; <script src="https://cesium.com/downloads/cesiumjs/releases/1.81/Build/Cesium/Cesium.js"></script>

</head> ;

<body>

<h1>Loading...</h1>

</div>

// Initialize the Cesium viewer.

const viewer = new Cesium.Viewer('cesiumContainer', {

imageryProvider: new Cesium.TileMapServiceImageryProvider({

url: Cesium.buildModuleUrl(" Assets/Textures/NaturalEarthII"),

}),

baseLayerPicker: false, geocoder: false, homeButton: false, infoBox: false,

navigationHelpButton: false, sceneModePicker: false

});

// This causes a bug on android, see: https://github.com/CesiumGS/cesium/issues/7871

// viewer. scene. globe. enableLighting = true;

// These 2 lines are published by NORAD and allow us to predict where

// the ISS is at any given moment. They are updated regularly.

// Get the latest from: https://celestrak.com/satcat/tle.php?CATNR=25544.

const ISS_TLE =

`1 25544U 98067A 21121.52590485 .00001448 00000-0 34473-4 0 9997

2 25544 51.6435 213.5204 0002719 305.2287 173.7124 15.48967392281368`;

const satrec = satellite. twoline2satrec(

ISS_TLE.split('\n' )[0].trim(),

ISS_TLE.split( '\n')[1].trim()

);

// Give SatelliteJS the TLE's and a specific time.

// Get back a long it More about this source textSource text required for additional translation information Send feedback Side panels History Saved Contribute 5,000 character limit. Use the arrows to translate more.