k 40 radio

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Magnetic Monster Loop Antenna for 160m - A monster magnetic loop antenna for 160 meters band. This Magnetic loop is optimized for 1840 Khz + 50 Khz. PDF Article published on La Radiospecola 10.22
[ Hits: 849 | Votes: 2 | Rating: 10 ]

20 / 40 Meter Short Coil Loaded Dipole Antenna - Experimenting a 20 40 meter short coil loaded dipole antenna with the goal to keep the total length under 40 feet so that the dipole can be mounted on two 20 foot fiberglass pole to make a 20/40 meter rotatable dipole.
[ Hits: 350 | Votes: 3 | Rating: 8.67 ]

Multi-band End-Fed Antenna - An excellent guide to homebrewing multi band end-fed antennas. The article, embed several drawings including diagrams and detailed pictures, illustrating the basic funcionality of end-fed antennas. The author gives some basic hints on how to build a half size antenna for 80 40 to 10 meters and a 6 meter to 40 meter configuration. It is also well described how to build the impedance transformer and the loading coils for lower bands.
[ Hits: 1105 | Votes: 6 | Rating: 4.5 ]
G4WIF End Fed Half Wave Antenna ^updated - Opting for a visually appealing inverted L configuration, G4WIF anchors the End Fed Half Wave antenna to an old clothes line pole, seeking cost-effectiveness in their endeavor. Despite initial misconceptions about transformer components, a £7.95 investment in a T240-43 toroid and DIY mounting container resolves the issue. Reflecting on commercial alternatives, G4WIF's homemade solution proves both economical and sufficient for their amateur radio needs.
[ Hits: 119 | Votes: 1 | Rating: 9 ]

End Fed Half-Wave Antennas - An interesting article on end fed half-wave wire antennas with a couple of original experiments. Author illustrate the role of the QRP matchbox, and a 40/20 meter antenna with a center stub making it a large bandwidth antenna for 40 and 20. Includes also an 80/40 end fed with the typical coil to make it available on 80 merts band.
[ Hits: 288 | Votes: 2 | Rating: 10 ]
End Fed Antenna with a 1:64 Matching Network - In this experiment the autor is going to explore the use of a 1:64 matching network on the End Fed Long Wire Antenna. Experiment will consist in build a 80-40-20-15-10 meter End Fed Long Wire Antenna with a 1:64 matching network from the documentation available on the internet
[ Hits: 872 | Votes: 15 | Rating: 6.73 ]
End-Fed Half-Wave Antenna for 20m 40m 80m - How to Design and Build a Field Expedient End-Fed Half-Wave Antenna for 20m, 40m and 80m. This Shorty 80m EFHW comprises a 49:1 autotransformer (to match the very high impedance at the end of a half-wave wire), a half-wavelength wire for 40m (also a quarter-wavelength for 80m), a loading coil and a short tail wire. The coil and the short tail wire (about 6 feet) make up the other quarter wave on 80m.
[ Hits: 141 | Votes: 1 | Rating: 4 ]

RF Choke with Bifilar Windings - This article presents an RF Choke featuring an 11-bifilar turn winding of #14 house wire on a Fair-rite FT240-31 toroid. The choke is enclosed in a 3D-printed case from Thingiverse, though this may pose thermal concerns at higher power levels. With SWR concerns up to 30MHz, the author plans to employ two series chokes at the rig input for improved performance. This choke offers versatility for portable use, with potential mismatch resolution using an antenna tuner. Further testing is anticipated upon the arrival of new cables.
[ Hits: 86 | Votes: 0 | Rating: 0 ]

Reversible 40 Meter Moxon ^updated - The author wants a compact, switchable antenna for 40-meter ham radio. They compare 3 designs: rectangle, short-tipped W6NL, and T-hat. All work well electrically, but mechanics matter for a large antenna. The rectangle needs strong support, while the T-hat is sturdier with slightly longer elements. The T-hat design wins for now, but the author will focus on its mechanical details next.
[ Hits: 74 | Votes: 2 | Rating: 5.5 ]

W3DZZ Multiband Antenna - An easy to build and extremely high performance antenna, works perfectly on all HF bands 3.5-28 MHz with some compromises, it is basically an half wave dipole for 40-80 meters, an LC circuit or trap 40 meters allows you to use a single radiating element.
[ Hits: 464 | Votes: 3 | Rating: 7.67 ]

WebSDR Wismar ^updated - This WebSDR is located in Wismar in the north of Germany JO53RV and operated by Frank Goehling DO7AX. There are four RTL2823U USB dongles with three Ham It UP up-converters for 80m/40m/20m and a RTL2832U for the 2m Band. The Antenna for 80/40/20m is a 84 meters Delta Loop.
[ Hits: 451 | Votes: 5 | Rating: 10 ]

Ribbit digital text messaging mode for HF/VHF/UHF - Ribbit is a novel digital text messaging mode for VHF/UHF communications for recreational and emergency use which radically increases the density of information transmitted by spectrum used. It leverages the computing power of the modern smartphone to increase the capabilities of any Handy Talkie without requiring any additional hardware or cable. A Ribbit message is fixed in duration at 1250 milliseconds. It is sent over audio modulation with a 2kHz bandwidth centered on 1.5kHz. It is preceded by 400ms of white noise to open analog squelch circuits.
[ Hits: 133 | Votes: 1 | Rating: 10 ]

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 ]

EA2CW QRP Portable radio setup - A portable QRP setup based on 20/30/40m QRP CW-only SW-3B transceiver, 2500mAh 5C LiPo battery (147g), Hands Free Nanokeyer
[ Hits: 105 | Votes: 0 | Rating: 0 ]

Hostilog - Hostilog is a logging program for HamRadio it uses a very easy way to enter qso data without any usage of a mouse. You can enter around 300 to 400 QSOs per hour from a paper written logbook, which is really quick compared to other logging programs. Combining and sorting of ADI Files are included
[ Hits: 62 | Votes: 0 | Rating: 0 ]

Common-mode chokes Measurements - Common-mode chokes are useful solutions for RFI reduction. Winding a few turns of coaxial cable on the FT 240-31 toroid can reduced the noise below the received noise floor. In this article author measure different chokes
[ Hits: 156 | Votes: 1 | Rating: 8 ]