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Antennas : Quadrifilar Helix

• NOAA Satellite Reception with QFH Antenna - How to receive NOAA weather satellite with a home made QFH Antenna. This project includes some easy and efficient notch filters to suppress noise from FM frequencies
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• 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 ]

• FunCube Dongle HF Upconverter: Expanding Reception Range - This article describes an HF upconverter for the FunCube Dongle Pro. Designed for radio amateurs, the converter extends reception capabilities to lower frequencies (0 Hz to 30 MHz) by mixing them with a higher oscillator frequency (100 MHz). This translates the desired signal into a range detectable by the FunCube Dongle (64 to 1,700 MHz). Key components include a double-balanced mixer and a low-pass filter to suppress unwanted signals. The project provides schematics, filter specifications, and design considerations for construction.
  [ Hits: 34 | Votes: 1 | Rating: 8 ]

• PCM Kestrel HF Transceiver - This article describes an upgrade to the Kestrel transceiver, replacing its LCD display with a 0.91-inch OLED screen for improved sound quality. VFO boards from Denys VK3ZYZ were integrated, particularly a Nano VFO board. The author shares details about the setup and the resulting enhancements, along with images of the modified components. The transceiver is now optimized for various frequencies and operates at a power output of approximately 120 W pep. More information about the boards can be found on the provided website.
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