frequency

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 ]

• Slim Jim Antenna Calculator by M0NWK - Easy to use online Slim Jim antenna calculator. Input your frequency to automatically calculate the lengths of the different antenna parts.
  [ Hits: 189 | Votes: 4 | Rating: 8.5 ]

• 20m Indoor Loop Antenna - This antenna can gets you on the air on 14MHz, and it has a useable frequency range. The VSWR is almost perfect at the centre-frequency abd the design uses no expensive components.
  [ Hits: 668 | Votes: 4 | Rating: 6.75 ]

• The W5JGV Loop Antenna - A Shielded Low Frequency Loop Antenna, allows Simultaneous Transmission and Reception at the Same Site.
  [ Hits: 257 | 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 ]

• 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: 342 | 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 ]

• Universal HF Tracker - The PCB can produce a High Frequency RF signal in the range of 1MHz to 12.5MHz using an AD9833 Direct Digital Sequence (DDS) frequency synthesizer. The signal can be modulated with different Weak Signal modes such as WSPR, JT9 and JT65 using our Arduino 5V/16MHz Pro Micro software.
  [ Hits: 144 | Votes: 0 | Rating: 0 ]

• RF Impedance Matching Calculator - Calculates the network to match a line to a specific complex load. This online tool calculates the matching network necessary to terminate a line of the specified characteristic impedence Zo in a specific complex load impedence RL + jXL at a specified frequency.
  [ Hits: 194 | Votes: 1 | Rating: 10 ]

• The G4AON SSB Transmitter - This transmitter covers the 160, 80, 40 and 20 metre bands and provides both SSB and properly generated CW. The CW side of this transmitter is not compromised and produces excellent CW. On SSB the audio has been tailored to provide a rising response to 3 KHz, with a sharp drop above that frequency. There is RF speech clipping to both provide more "punch" and to limit the peak output.
  [ Hits: 181 | Votes: 2 | Rating: 9.5 ]

• 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 ]

• Simple 2.4 GHz SWR Meter - This is a simple 2.4 GHz SWR meter which is based around surplus microwave hardware which can be easily found. The main component is a MECA -20/-20 dB Directional Coupler which has a frequency range of approximately 700 MHz to 2.5 GHz.
  [ Hits: 143 | Votes: 2 | Rating: 6 ]

• 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 ]

• USB Rig Interface - This project is a USB Audio, Serial and PTT interface for rigs that does not directly support digital modes provided by applications such as FLDIGI, WSJT-X and JS8CALL. Plug these interface devices into your Windows or Linux laptop or Raspbian Raspberry Pi and you can send and receive digital tones to/from your rig and automate the frequency and mode control and PTT control.
  [ Hits: 321 | Votes: 1 | Rating: 1 ]

• 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: 149 | Votes: 2 | Rating: 10 ]

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