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Category «Circuits»

SSM2167 Microphone Preamplifier with compression for ubitx HF Transceiver

SSM2167 Microphone Preamplifier with compression for ubitx Transceiver

SSM2167 Microphone Preamplifier with compression for ubitx HF Transceiver This DIY project idea based on the small board module “SSM2167 Microphone Preamplifier Board Preamp Compression Module DC 3V-5V” widely available on eBay and Aliexpress. Mic gain is barely adequate on the µBITx transceiver since there is no Mic Gain control. It would also be helpful …

VK3YE’s AGC circuit for ubitx

agc circuit

      VK3YE’s AGC circuit for ubitx An ubitx AGC board is a circuit board that can be installed in a ubitx transceiver to provide automatic gain control (AGC). AGC is a feature that automatically adjusts the gain of the transceiver’s amplifier to maintain a constant audio output level, regardless of the strength of …

Ten Minute QRP Transmitter


Ten Minute QRP Transmitter The design apparently originated in 1996 in an amateur radio club QRP publication.  The name originates since the original author claimed he built this transmitter and make a QSO with it in just 10 minutes time. There are no coils to wind  it tunes a wide range of crystal frequencies, and it outputs an …

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 …

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 …

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.

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.