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Yagi Uda Antennas
Optimized 10-element UHF Yagi Antenna
The elements diameter of the antenna may vary between 5...8mm and the dipole diameter may vary between 8...12mm (12mm recommended) without the need of changing anything to the length or spacing. All elements except the dipole are electrically connected to the boom and may be mounted on top or through it.
J-POLE for VHF/UHF
SWR can be adjusted by adjusting the connection point L3 figher or lower.
VHF/UHF Dualband vertical
Use for this antenna tube of 10mm diameter. Or you can use a brass rod of about 7mm diameter. The top one is a strong copper (brass) wire of 5 to 7 mm diameter soldered directly to the coil and mounted to the PVC isolator to give a strong construction.
Quarter wave vertical antenna
To calculate the length of the elements of other bands use the above formula. Example 6 meter band (50Mhz): (75/50)*0.96=1.44 meters
Full wave omnidirectional
This is a Full wave omni directional vertical ground plane antenna for 2-meters plan with 250 watts max power.
VHF Portable "rubber duck" antenna
You can make your own 2-meter "rubber duckies" that will likely perform much better than many commercial units. I compared my design with two other "rubber duckies" of the TH215 and ICT7 which outperformed them both. With the "duckie" of the ICT7e as much as 10dB. It does not has a gain compared to a 1/4wave antenna ofcourse, but compared to...
UHF 3-element portable
This design notes shows a UHF 3-element portable antenna with gamma-match.
VHF/UHF Wideband Portable Dipole
I wanted a robust, portable, compact antenna usable for horizontal and vertical polarisation to take along with my FT-817 when I go on vacation, camping etc. I also wanted the dipole to cover the VHF and UHF bands and if possible with some gain! As everybody knows a dipole has about 3dB gain over a quartre wave antenna, is why my preference went...
Vipor mutant portable HF/VHF/UHF
Most of us don`t have the luxury of building a 1/4, 1/2 or even a 5/8 wavelength vertical antenna for HF. We have to settle for something a little shorter. (A lot shorter, in the case of people following the FCC`s Part 15 rules, which limit them to 3 meters in size.) Shorter vertical antennas can give acceptable (but not spectacular) performance.
Q-Multiplying Loop Antenna
This circuit is designed to be used in conjunction with the standard 4 foot square loop used in MW for long distance reception.
ATL-3 Loop Antenna
This antenna is the result of long term development and user feedback. All ATL-3 loop windings are centre tapped and balanced w.r.t. their amplifier/receiver chassis ground, and therefore electric field interference pick up tends to self cancel. Magnetic noise fields,e.g. televisions and the electric meter box, or electromagnetically radiated...
QRP Antenna Tuner
This circuit is for a QRP (low power) antenna tuner, a.k.a. a transmatch, for use in the short wave amateur radio bands from 3-30 Mhz. It allows a wide variety of antennas to be connected to a low power transmitter. When the circuit is properly tuned, the maximum transmitter power will be delivered to the antenna. It is used in conjunction with...
RF Dummy load
The load described here is capable of handling up to 10 watts of RF power for a couple of minutes, and is designed for the widely used 50 ohms impedance. It consists of ten parallel connected 560 ohms 1 watt resistors, R1 through R10, a voltage divider, R11-R12, and a rectifier D1-C1. Apart from loading the transmitter output with a minimum of...
Loop antenna for 187 KHz
This 1 square meter antenna has radiation resistance of about 10 nanohoms, making the 0.4 Ohm resistance (including skin effect, which about doubled the resistance from the DC value) the dominant loss in the antenna. The lower the resistance, the more efficient it would be - and from these numbers, efficiency is nearly directly proportional to...
Tiny Tuned Loop Antennas
Loop Antennas are considered to be "samall" when their diameter drops below about 1/10 of the wavelength they are intended to be used at. In this case, I use the term "Tiny" because the antenna's diameter is about 1/30,000 the wavelength, and at 5.5 cm in diameter, they are quite small in human terms. Coils are one of the few components...
Antenna ground loop Isolator
A ground loop in your AV system caused by antenna connection or TV cable is very common if you have your computer connected to the same system. This type of ground loop problem can be solved by using suitable isolation between your AV system and the antenna cable. The simplest way to get rid of the hum is to disconnect the antenna cable from the...
Dipole antenna for two metres
Described here is a simple omnidirectional, vertically-polarised dipole for two metres. Made from coaxial cable, it can be rolled up and stored in a small container. It may be used as is indoors, or waterproofed for use outside. No extravagant gain claims are made; this dipole has no more gain than any other. However, it should be significantly...
AM loop antenna project
A loop antenna can greatly improve medium wave reception. Loop antennas are directional and receive signals along the plane of the windings. The directional quality improves signal to noise ratio of the desired signal while rejecting signals perpendular to the plane of the windings. Larger loops are better than smaller ones but good results...
low noise receive aerial
This afternoon I have returned to 10m WSPR. There are lots of transatlantic reports of my signal, as well as reports of my 2W signal from Russia and Brazil. Sackville Gardens springing into bloom - Sackville Gardens is one of too few oases in Manchester city centre, and for a couple of weeks each year its trees can parade themselves, almost peacoc
FM Radio Circuits
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FM Transmitter Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
Digital Signal Integrity
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