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Category «DIY»

Circuits – Sovina2 40M Class E Transmitter

sovina tx

Adaptation of Class E amplifier for amateur radio application is very rare due to inherent difficulties in filter design associated with it till release of usdx transceivers. The above compact transmitter uses class E amplification with three BS170 mosfets, a popular approach in usdx final. What’s new is the oscillator…any similarity with the NS40 is …

Terminated End Fed Vee Antenna (TEFV)

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 …

Circuits – Simple Crystal Tester

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 …

Circuits – 40M tag QRP Transmitter

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.

Circuit – FM Bandstop Filter for RTL SDR

fm trap

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 …

DIY – Making printed circuit boards

pcb making

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 …

Circuits – Offset tuning indicator for CW


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 …