Recent Posts

40m DC-receiver – VFO

So the receiver is alive and kicking and I have received amateurs from The Netherlands, UK and Italy on a simple 10m wire antenna. However, the VFO is comprised of a Siglent SDG1032X function generator from work. Hardly a self-contained solution!After an article by Bill Merea in the GQRP Sprat magazine, I’ve decided to […]

Milliohm meter

This is a simple but accurate milliohm meter with a range of 0 – 2000 milliohm (= 2 Ohm). It has a typical accuracy of 2%-3%. Unlike other designs this circuits doesn’t use large currents to measure these small resistances. So there is no risk to damage components. A small alternating current is used […]

40m DC receiver – “It’s alive!”

With a three day Pentecost weekend and my wife away on a camping trip with my son, I had some time to look into the receiver again. With the previous series of tests, I’ve found that product detector was working fine and featured good conversion gain. The LO oscillator injection was flawed because the […]

Double-balanced cross-coupled product detector

Winner of the G2NJ Trophy 2022 !!!

The double-balanced cross-coupled product detector had a brief stint of popularity in the 70s and 80s. It’s popularity quickly faded once integrated product detectors like the Plessey SL640, Motorola MC1496/1596 and the CA3028A came on the market. Offering ease of use and further integration. My attention […]

JFET testing

For an upcoming RF amplifier project I needed a couple of JFETs. The spread in device characteristics is quit broad. For the BF256B Vp ranges from -0.5 to -8.0V ( a factor 16! ) and IDSS ranges from 6 mA to 13 mA. Since, I bought a small stock of them, I decided to […]