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End-Fed Half Wave matching unit project, based on a FT140-43 with SWR plot tests made using capacitor and without.

A trapped multi band end-fed-half-wave antenna for 40/30/20/17/15m.

A multi band antenna for HF band capable to operate from 10 to 80 meters band depending on wire lenght loaded with a small inductance neat the feed end.

An end-fed half wave antenna matching unit made of 3:24 turns ratio on a FT140-43 toroid with a 150pF capacitor across the input.

A project to turn a Raspberry Pi into a very versatile tracker, digipeater and an iGate

Experimentin wire antennas on top band using several type of aerials. This includes a 40 to 160 meters EndFed Half Wave kite antennas and 160m/80m loaded vertical antenna.

A portable loop antenna, made with a 3 meter loop resonates with the chosen capacitor from just below 7MHz to about 28.300MHz which makes it usable on the bands from 40m to 10m.

This project involved designing a 7-pole Chebychev broadcast band filter to address severe interference issues caused by a new horizontal loop antenna on the KN-Q7A transceiver. The interference overwhelmed the transceiver’s front end, so a custom filter with a 3.5 MHz cutoff was built using silver mica capacitors and type 6 T130 toroidal cores. Encased in a diecast box with SO239 sockets, the filter blocks strong signals from the broadcast band, achieving over 100 dB attenuation. Tested up to 100W, it reduces interference effectively while maintaining low insertion loss across HF bands.

This article reviews a custom-built, pressure-sensor-based CW paddle, designed by VK3IL, as an alternative to the stock _Elecraft KXPD2_ for the _Elecraft KX2_ transceiver. The author, VK3PF, describes recurring issues with the mechanical KXPD2, including intermittent operation and loosening screws, which prompted the search for a more reliable solution. The pressure-sensitive paddle utilizes a PCB and components provided by VK3IL, requiring surface-mount device (SMD) soldering for assembly. The physical housing for the paddle is a DIY "sandwich" construction, employing two pieces of closed-cell foam around the PCB, secured with heat-shrink tubing. This design allows for comfortable, single-handed operation, particularly beneficial for portable activations like Summits On The Air (SOTA). The paddle connects to the KX2 via a 3.5 mm stereo plug, and its operation involves squeezing the foam-encased assembly to generate dits and dahs. The successful implementation has led to the complete replacement of the original Elecraft paddle.

The Pressure Paddle V2.0 simplifies the original 2019 design by using MOSFETs’ unique properties for reliable, minimalistic switching. When pressure sensors detect a press, they reduce resistance, activating the MOSFET and lowering voltage until it stabilizes at the MOSFET’s threshold. This ensures consistent “key down” signals for the transceiver. Compatible with 3-5V logic systems, the circuit operates independently of pull-up resistor size. The PCB is lightweight, easy to assemble, and can be packaged in heat shrink or mounted. This version maintains durability with fewer components and flexible packaging options.