NE602 40m DC Receiver

Updated : January 25th; Input amplifierUpdated : January 26th; Audio filter

A couple of days ago I found the circuit of 20m DC PSK31 receiver at the website of va3iul. The website of va3iul is probably well known in the radio amateur community. It features 100’s of circuit design ideas on all kind […]

Simple remote numeric keypad with ATmega88

Numeric keypad for radio control

Numeric keypad for radio control […]

Easy to Customize Universal Low Pass Filter

PA3COR - Universal RC Low Pass Filter fc = 3.3KHz

A universal low pass filter that can easily customized, uses easy to obtain parts and has low power consumption. […]

1 transistor CW – filter

You cannot get it more simple than this, a 1 transistor CW filter. This filter is build according to the (surprise !) Multiple Feedback BandPass Filter (MFBPF) topology. Below, you see the circuit, originally designed by KE3IJ (alas now SK).

[…]

40m DC Receiver – CW Filter

So after studying some designs of multiple feedback band-pass filters for CW by other designers (see my previous post), I’ve decided to try my hand at designing and building one myself. Actually, I’ve made two different versions. The first one is designed by myself and is a two stage filter with an fc of […]