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So when you have a bunch of jellybean JFETs (2N5457), time to burn, and a handful of 1uF bipolar capacitors…
What to do..

I decided to build a simple amplifier Although many find JFETs aren’t quite as intuitive as a regular BJTs, they’re not THAT scary and they’re easily biased, using a megaohm sized resistor from the gate to ground.

To be able to do some more accurate calculations, I decided to measure the maximum drain current, IDSS, and the negative Gate-Source cut-off (pinch off) voltage, as they can vary significantly even between devices even from the same batch.

A fun evening in the lab

This weekend was special: yesterday the baltic countries: Estonia, Lithuania and Latvia, disconnected from the Russian/Belarus 50Hz power grid, going ‘island mode’, controlling the 50Hz grid frequency themselves.

After more than a day of different stability tests, this afternoon, just before 13:00 CET, a connection to the European grid was established via Poland, so now the the three countries are in 50Hz sync with Europe.

I observed a small, undramatic, ‘burp’ in the frequency at the time of the event, and my wall socket is now in full sync with the measurement in Estonia, provided by #sympower️

1/2)
A fellow #hamradio operator and electronics enthusiast brought me a vintage X-Band power sensor, thanks OZ1ETE

It has a super sensitive NTC Thermistor, a tiny spherical bead, encapsulated inside a small glass tube. It’s by far the most sensitive Thermistor I’ve ever seen, just holding your hand in front of the waveguide flange, not actually covering it, will make it change slightly.
#rfengineer #rfengineering #electronics #testandmeasurement #sensorsunday

Occasionally you come across a rescue scenario: it was literally me or the dumpster… So I adopted it, I now have a 20GHz frequency counter…

The 5361B was never made for normal RF use, its primary application is analysis of pulsed radars. It does, however, fully support CW measurements, so although somewhat bulky, it’s a nice instrument to have around in the lab

I’ve been looking for an antenna for a permanent #meshtastic node in my attic and I found this one, along with 5m RF200 low-loss cable.

I know that this setup will most likely render me ‘excommunicado’ in the #meshtasticcommunity: “thou shalt always install thy node right below the antenna!”, but here’s the thing: I want to experiment with different hardware, I want to do some interference measurements at night (ever heard about the ‘Mammotion’ lawnmower which illegally jams 868MHz?) , AND I have a powerful 2m/70cm transmitter close to it, and I don’t want EMI issues on a sensitive 5V line.

Besides, the antenna has 3dBi gain and I measured the cable loss to 1.4dB at 868MHz, so given its better location, the numbers still come out positive

See that dip near 145MHz btw.? Need to do a test to see how much signal it’ll pick up from my VHF rig - don’t want to damage my LoRa module

#lorawan #electronicsengineering #rfengineering #rfengineer #hamradio hamr #testandmeasurement

It’s #sensorsunday

A field strength meter can be really handy when testing antennas and they’re simple to build: a couple germanium diodes, a capacitor, a good old analog uA meter and a potentiometer to adjust the sensitivity.

This unit was just $20 and it seems they repurposed a PCB originally intended for some other application

To use it, start by adjusting the sensitivity to its minimum setting, key the transmitter at its lowest power (1W will certainly do) and walk along the antenna and measure the field strength along the wire or structure.

I’ll do a future post demonstrating it on a trap dipole , W3DZZ style

#Easterquiz, what is this?

Correct answer and a demo will follow one of these days