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.
Year archives: 2022
Antenna – Foldaway Loop antenna
This loop antenna is based on one published in one of back issues of sprat by DL1HCU. It worked well with QRP power from 20-10 metres, including WARC bands. The tuning capacitor is twin gang type salvaged from old radio.
Antenna – Rockloop Compact HF antenna for 10,15,20 metre ham bands
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.
Circuits – Pippin QRP Transmitter
This pippin QRP transmitter is basically a conventional colpitts type crystal oscillator with output taken from a low value collector load resistor and direct coupling is made into the base of PNP transistor used as an amplifier. This simple circuit develops around one watt output with 12V as power supply.
Circuits – Battery Low Power Indicator
Circuits – Battery Low Power Indicator – This circuit provides a flashing pilot indicator for equipment where low battery drain is essential. The LED flashes approximately once per second and total drain current is only 320 microamps.
Circuits – 7 Mhz 5 Watts CW Transmitter
The above 7 Mhz 5 Watts CW transmitter circuit was found in one of back issues of sprat. Still i am wondering how 5 watts juiced out from this tiny crystal oscillator circuit.
Circuit – FM Bandstop Filter for RTL SDR
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 …
Circuits – Simple zener diode tester
Simple zener diode tester Circuit – FM Bandstop Filter for RTL SDR
DIY – Making printed circuit boards
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 …
Video – Colombo International Radio Tamil service Inaugural day transmissions
Colombo International Radio Tamil service – Inaugural day transmissions Frequency – 873khz Time – 7.00 am to 8.00 am