low frequency

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low frequency

87 links - and 2 categories

Antennas : 20M : 20 meter Dipole Antennas
  • 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: 231 | Votes: 1 | Rating: 9 ]
Antennas : Antenna Calculators
  • Calculate Antenna Lenght in feet, inches and meters - Inches and meters Javascript Wavelength Calculator allow to input a frequency in MHz and calculate wavelenght in several units considering also fractions of wavelenght and the velocity factor. Includes an usefull inch to meter converter
    [ Hits: 502 | Votes: 3 | Rating: 4.67 ]
Antennas : Horn
  • 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 ]
Antennas : Loop
  • The W5JGV Loop Antenna - A Shielded Low Frequency Loop Antenna, allows Simultaneous Transmission and Reception at the Same Site.
    [ Hits: 256 | Votes: 0 | Rating: 0 ]
Antennas : Portable
  • Balcony Mounted Buddistick Antenna by KP4MD - The antenna handles 250 watts and covers 40 through 10 meters, with an optional add on coil for 80 and 60 meters. The author in this pages includes an interesting video in which describes the antenna setup, and the importance of the shunting coil on lower bands like 40 and 80 meters. SWR curves diagrams are also included and demonstrate the influence on resonating frequency of the shunting coil.
    [ Hits: 279 | Votes: 3 | Rating: 10 ]
Antennas : Receiving
  • Receiving Loop Antenna - A receiving loop antenna for low frequency DX Work
    [ Hits: 756 | Votes: 0 | Rating: 0 ]
Antennas : T2FD
  • T2FD Antenna - Terminated and twisted folded dipole - T2FD is a 600-900 ohms folded dipole, terminated with resistor. Feed impedance is coupled with 50/600 ohms voltage balun. It is a wide band antenna with rather low SWR over the full designed frequency range: antenna tuner is seldom needed.
    [ Hits: 482 | Votes: 0 | Rating: 0 ]
Manufacturers : Antenna Analyzers
  • HG7AN Antenna Analyzer - Antenna Analyzer plus 500 is a multifunctional measuring instrument, very useful for amateur radio activity. Its size allows you to easily take it for relocation as well. Frequency range: 100KHz - 500MHz. Access directly via WiFi. Includes a dual-channel signal generator
    [ Hits: 264 | Votes: 1 | Rating: 10 ]
Operating Modes : Morse code : Learning Morse Code
  • 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 ]
Propagation : Propagation Forecast
  • 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: 168 | Votes: 0 | Rating: 0 ]
Radio Equipment : HF Transceivers : Yaesu FT-950
  • Yaesu FT-950 CAT Manual - The CAT (Computer Aided Transceiver) System in the FT-950 transceiver provides control of frequency, VFO, memory, and other settings such as dual-channel memo- ries and diversity reception using an external personal computer. This allows multiple control operations to be fully automated as single mouse clicks or keystroke op- erations on the computer keyboard.
    [ Hits: 57 | Votes: 0 | Rating: 0 ]
Radio Equipment : HF Transceivers : Yaesu FT-991
  • FT991 MARS Mod - This modification will expand the tx frequency range of the Yaesu FT-991 from allowing just ham radio bands, to all bands 1.8 - 30MHz and 50-54 MHz.This information is solely for use by licensed members of MARS (Military Affiliate Radio System) or CAP (Civil Air Patrol)
    [ Hits: 917 | Votes: 5 | Rating: 3 ]
Radio Equipment : Receivers : Icom IC-R75
  • ICOM IC-R75 Review by N9EWO - Icom IC-R75 tabletop HF communications receiver came onto the market back in 1999 and was taken out of production in late 2015. Frequency coverage is from 30 hz right to 60 MHz. This allows one to catch the 6 Meter amateur band as well.
    [ Hits: 44 | Votes: 0 | Rating: 0 ]
Software : Antenna analysis
  • Zplots - Impedance Plots with MS Excel Charts - Zplots is an Excel application that allows you to plot impedance and related data obtained from a variety of sources. You can plot on both an XY chart and a Smith chart as well as view the data in tabular format. The XY chart can be customized with your choice of trace lines. Frequency (in MHz) is always shown on the X axis.
    [ Hits: 296 | Votes: 0 | Rating: 0 ]
Technical Reference : Audio
  • 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
    [ Hits: 71 | Votes: 0 | Rating: 0 ]
Technical Reference : Calculators
  • Bandpass Filter Calculator - Passive Bandpass Filter online calculator and filter formulas. Active Inverting Op Amp Bandpass Filters, Active Noninverting Op Amp Bandpass Filter, just enter the Low ir High Cutoff Frequency
    [ Hits: 156 | Votes: 3 | Rating: 5.33 ]
Technical Reference : Radio Frequency Interference
  • Ham Radio TVI in the 21st Century - Ham radio transmissions can interfere with television reception. This is called television interference, or ham radio TVI. Consumer adoption of cable television has significantly reduced ham radio TVI. But the introduction of IPTV, or television over phone systems, has brought ham radio TVI back, often with a vengeance. Here's why
    [ Hits: 322 | Votes: 0 | Rating: 0 ]
Technical Reference : Test Equipment
  • Precision VXO - The Precision VXO (PVXO) and its matching Crystal Test Fixture (CTF) were created to provide a low cost means of evaluating the characteristics of crystals and a means of measuring their series resonant frequency.
    [ Hits: 208 | Votes: 1 | Rating: 1 ]
Technical Reference : Test Equipment : Signal Generator
  • ADF4351 Signal Generator - Just a simple signal generator based on ADF4351 module from fleebay allows you to generate one single frequency that can go up or down in 100Khz steps via two push buttons.
    [ Hits: 148 | Votes: 2 | Rating: 10 ]
Technical Reference : Transverters
  • 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: 77 | Votes: 0 | Rating: 0 ]

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