Electronics and Technical resources from vu3dxr
Terminated End Fed Vee Antenna (TEFV) Author : D.Prabakaran VU3DXR Figure1 – Terminated End Fed Vee antenna It is a travelling wave antenna, which has a constant current distribution along its length. Antennas usually used by radio amateurs are resonant standing wave types like dipoles. It is built to a specific tuned length so that …
Simple Crystal tester – The idea for this crystal tester circuit sprung out of the need of testing a large number of oscillator crystals lying unused in a big hobby box. testing the crystals one by one without the appropriate device would have been very slow and a time consuming task. Commercial crystal testers are …
Here is another qrp cw transmitter pulled out from SPRAT back issues, which is simple to build with commonly available components from every one shack. We can subsititute 2N2222 for BC108 and BD139 for BD 131.
Rockloop DIY Compact HF antenna for 10,15,20 metre ham bands This rock loop antenna tunes to 15 meter band with 15 to 20pf,20 meters with about 30pf, and 30 meters with about 60pf, much suitable for apartment dwellers and QRP Portable operations.
FM Bandstop Filter for RTL SDR The given FM band stop filter is nothing more than a simple Band stop filter for the frequency range of 88-108Mhz. FM Broadcast transmitters transmit at high power and can cause overloading and intermodulation problems on simple receivers like RTL-SDR due to its wide open front end. The said …
Simple zener diode tester Circuit – FM Bandstop Filter for RTL SDR
Making printed circuit boards There are many ways to produce your own printed circuit boards. Small boards for DC switching circuits are easy to make because neither the size nor the shape of the copper foil traces is critical. Boards containing many digital ICs are considerably harder to lay out and etch. There are also …
An NE567 tone decoder, tuned to the transceiver`s CW offset frequency, ensures that the transceiver will be transmitting on the same frequency as the received CW signal. Simply tune the transceiver so that the LED lights. Eight to 13 Vdc is required; this can be taken from the transceiver supply or an extra battery. Audio …
DIY – 137 Mhz V-dipole antenna for weather satellites reception D.Prabakaran VU3DXR A V-dipole for NOAA weather satellites on 137 MHz has been published by 9A4QV and it seems to get very good results. The designed antenna works at frequency 137 Mhz with omnidirectional radiation pattern. The length of the each leg should include the …
This low-cost circuit is suitable for powering flashlights, emergency lighting and other applications in which it is desirable to power white LEDs from one or two primary cell batteries. The transistor, lk resistor [Rll and the tapped inductor form a blocking oscillator. When the power button is pressed, the transistor …