This video provides a basic introduction to voltage standing wave ratio (VSWR) and return loss, and explains how these measurements are used in radio frequency applications.

Episode 1254 chip of the day
CD40106 Hex Schmidt Trigger Inverter

Viewer comments:

The 74HCU04 which is the un-buffered version of the ‘HC04, is praised as capable of low phase noise when used as crystal oscillator. Also, these un-buffered cmos inverters are quite versatile as they behave quite linearly when biased as analog inverter amplifiers.

Be aware that if you order a cheap CD40106 from China you may get a repainted 74HC14A instead. If you plan on using it at 5V or less this is fine, but unlike the 74Cxx and CD4000 series chips which have an absolute maximum VCC rating of 18V, the 74HC ones are only good up to 8V. I designed and built an automotive control circuit using a “CD40106″ and couldn’t figure out why it worked perfectly on the bench (using a 5V supply) but kept failing completely after just a few hours of use in the car at 12V (or 13.8V). It took me a while and a half-dozen fried “40106′s” to figure out that my 40106 wasn’t actually a 40106. The vendor had simply rebadged 74HC14 chips as CD40106/74C14. Caveat Emptor.

In this video I use the TDR (low-pass step function) transform feature of the NanoVNA V2 to verify that I have an outside antenna problem on my roof, and not a coax cable problem located inside. This serves as a field-expedient way to identify the location of an antenna system problem that can be easily done with any NanoVNA.

0:00 Preface
1:22 Background Info and TDR Setup
4:52 SOL 1-Port Calibration
5:54 TDR Distance to Fault Measurements
9:20 Pre-Maintenance Return Loss Checking
11:07 Post-Maintenance Results Summary
12:50 End

I constructed the Veritasium electricity thought experiment in real life to test the result.

If you were watching my community posts a month ago, the day that Derek over on Veritasium posted his video about electricity misconceptions, you saw me obsess over that problem a bit too much and immediately use it as the excuse I’ve been looking for for years to own my own oscilloscope. Instead of two light-seconds of wire, I used about 3 light-microseconds of wire, but it was PLENTY to resolve exactly what is happening in this circuit. I hope you enjoy the analysis!