Half Rhombic antenna with counterpoise
Half Rhombic antenna with counterpoise was published in RSGB Radio Communication magazine December 1996 page 62. Refer for more info about broadband terminated end fed antenna here.
Monthly archives: January, 2022
Circuits – LM386 Audio oscillator
LM386 Audio oscillator This one is excellent application of widely used audio amplifier IC LM386.Its output is square wave at no load condition. Its frequency is governed by supply voltage. It can be used as code practice oscillator, even as side tone for your qrp radio. The LM386 is an widely abused integrated circuit containing …
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.
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.