radio frequency

radio frequency

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• 20 meter short loaded vertical antennas - Loading is a way to lower the resonant frequency of an antenna radiator. This technique is typically used in antennas that have radiating elements that are too short for the desired resonance frequency. In this excellent article the author experiment loaded vertical dipoles for 20 meters band
  [ Hits: 232 | Votes: 1 | Rating: 9 ]

• What is Horn Antenna - Horn Antenna - The energy of the beam when slowly transform into radiation, the losses are reduced and the focussing of the beam improves. A Horn antenna may be considered as a flared out wave guide, by which the directivity is improved and the diffraction is reduced. One of the first horn antennas was constructed in 1897 by Bengali-Indian radio researcher Jagadish Chandra Bose in his pioneering experiments with microwaves. The modern horn antenna was invented independently in 1938 by Wilmer Barrow and G. C. Southworth. This Horn model antenna is suitable employed in the UHF or SHF radio bands. Making this horn model antenna it will be easy for a beginner to make if it works in the 10GHz frequency, because small dimensions so it is not so difficult and also offers gain up to 25dBi.
  [ Hits: 74 | Votes: 0 | Rating: 0 ]

• Trapped vertical Antenna - This antenna is an omnidirectional and multiband and it is well suited for DX enthusiasts with limited space. Each of the parallel circuits (trap) behaves like an isolator on its resonant frequency.
  [ Hits: 356 | Votes: 7 | Rating: 2.71 ]

• Radio Scout Frequencies - Information on frequencies suggested as Scout amateur radio frequencies. These were initially suggested by the World Organization of the Scout Movement and their Jamboree on the Air organizer. As with all amateur radio frequencies they are a shared resource. If someone else is already on that frequency, move up or down to find a clear frequency for calling.
  [ Hits: 45 | Votes: 0 | Rating: 0 ]

• Satellite Frequency List - All Satellites Frequency List Update. A complete list of satellite frequencies available in several formats, including info on Satellite Uplink and Downlink frequencies Beacon, operative Mode, Callsign and Weather sat functionality.
  [ Hits: 140 | Votes: 1 | Rating: 1 ]

• Recognition of CW signs at different listening levels and frequencies - The recognition of telegraphy masked by noise at 40 and 80 signs/min telegraphy speed was studied in 10 normal-hearing subjects at different sound pressure levels (25-85 dB SPL in steps of 5 dB) as well as at different test frequencies (2000, 1000, 800, 630, 500 and 250 Hz). The ability to recognize the signs varied with varying SPL. Recognition for most of the subjects was best at an SPL close to 70 dB. All subjects improved their recognition as the frequency was lowered to 500 Hz, some even at 250 Hz. These facts should be taken into consideration when training telegraphy operators as well as in the construction of radio receivers to permit listening at low frequencies. Furthermore, the critical ratio was calculated at the different test frequencies.
  [ Hits: 81 | Votes: 1 | Rating: 7 ]

• Ham Radio: Using Repeaters - The most basic form of repeater receives communication on one frequency and re-transmits at a different frequency. This is known as duplex communication. Repeaters are generally set up to operate with FM modulation on the amateur bands within the VHF (30 MHZ – 300 MHZ) and UHF frequencies (300 MHZ – 3 GHz). These are generally the frequencies used by handheld and mobile devices.
  [ Hits: 92 | Votes: 1 | Rating: 8 ]

• Calculation of the Maximum Usable Frequency - This paper presents the method of calculating the maximum usable frequency (MUF) and field strength of radio waves reflecting 2 times at the F2 ionosphere layer under inhomogeneous conditions of the ionosphere. The comparison between predicted and measured MUF has shown that the proposed method significantly increases the accuracy of calculation MUF.
  [ Hits: 242 | Votes: 2 | Rating: 5.5 ]

• HF communication prediction tools - Online HF Communication prediction system provided by the Australian Governament Buerau of Metereology allow to predict usable frequency rage for radiocommunications between two stations allowing to specify frequency and date range. This tool allow calculation with different methods and algorithms
  [ Hits: 169 | Votes: 0 | Rating: 0 ]

• Transforming the Elecraft K3 into a SDR with K3 - This article will explain a few of the ways author use an external SDR and Linrad to enhance his K3 experience. Linrad is one of many available SDR receiver programs. The same could be done with any radio that lets you access its IF frequency output. Article from NCJ Nov Dec 2019
  [ Hits: 343 | Votes: 0 | Rating: 0 ]

• Icom 706MkIIG Frequency Calibration - Unlike older radios, the 706 uses only one crystal oscillator (called the Master Oscillator). All other frequencies in the radio (L.O., 3-4 I.F. stages, VFO, and CW-offset) are computer-derived from the Master Oscillator. This makes it relatively simple to frequency-align the radio, so that it agrees with the Frequency Display in all modes.
  [ Hits: 214 | Votes: 2 | Rating: 9 ]

• Speech synthesiser for FT-817 - This construction project is for anyone wanting to give this popular little radio a voice of its own. This Speech synthesiser reads out the current frequency, mode and menu settings whenever they are changed via the front-panel controls
  [ Hits: 124 | Votes: 0 | Rating: 0 ]

• LAN-IQ SDR - Stand Alone Software Defined Radio, direct sampling receiver from 30 kHz to 1700.00MHz continuous frequency range, LAN interface for remote access
  [ Hits: 258 | Votes: 1 | Rating: 8 ]

• UK Scanner Frequencies - UK frequency list provide reference table to lister to Police scanner channels UHF VHF, Amateur Repeaters, Ambulance CB Radio CoastGuard Rescue, marine VHF, Military and more.
  [ Hits: 163 | Votes: 1 | Rating: 1 ]

• Repeater-START App - The amateur radio listener for when you're not on the radio. Repeater-START, the offline repeater listing app for Windows, Linux, Raspberry Pi, Ubuntu, Librem Phone is available, Now with grid square display, topographical maps and frequency preferences
  [ Hits: 151 | Votes: 0 | Rating: 0 ]

• A switched Capacitor Audio Filter - Here is a rather nice audio filter for use with Ham Radio gear. It features switchable operation as a -32 dB per octave low pass or notch filter having a 200Hz-2500Hz tunable cutoff frequency, buffered input and output, switch selectable filter bypass function, and good stability. T
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• Gimme Five - QRP SSB Transceiver - Gimme Five reloaded, a compact 5 band QRP SSB transceiver in SMD technology. This unit covers 5 bands within the amateur radio spectrum (3.5, 7, 14, 21 and 28 MHz). Receiver is a single conversion unit with an interfrequency of 9 MHz. Transmitter uses 5 stages and has got a power level of 10 watts PEP output.
  [ Hits: 285 | Votes: 1 | Rating: 10 ]

• Understanding computer-generated RFI - Radio Frequency Interference (RFI) has always been a source of concern for the Radio Amateur. Until the recent introduction of complex circuitry in the home, our communications gear has been the main source of potential RFI. In this computerized age of ours, increasingly complex and sensitive receivers are being barraged by these and other sources of RFI.
  [ Hits: 84 | Votes: 0 | Rating: 0 ]

• SDR Receiver with RTL-SDR and Gnu Radio - This project is a Software Defined Radio Receiver. It has a frequency range of 24MHz 1.2GHz. It can demodulate AM, FM, USB, LSB with selectable bandwidths of 600, 2400, 2800, 3200 and 6400Hz. Using a simple RTL-SDR Dongle and Raspberry Pi 3 computer using GNU RADIO
  [ Hits: 484 | Votes: 1 | Rating: 1 ]

• 2m to 70cm Transverter Circuit - A 70cm / 432 MHz Transverter Project transverter circuit is an electronic device that converts a radio signal from the 2 meter to the 70 centimeter band and vice versa, allowing a single transmitter/receiver to be used for both bands. It consists of an IF stage, local oscillator, frequency multiplier, and amplifier. The circuit must be designed for minimal signal loss, noise and intermodulation distortion.
  [ Hits: 81 | Votes: 0 | Rating: 0 ]

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