Search Results for: length matters

Common mode choke measurement – length matters #4

Common mode choke measurement – length matters #2 discussed the effect that even quite short pigtails might have on the measurement of a high value resistor. This article documents an experiment to measure a DUT comprising two 1206 0.1% 10kΩ resistors soldered to a 2w section of turned pin male header strip. Above is the … Continue reading Common mode choke measurement – length matters #4

Common mode choke measurement – length matters #3

Following on from Common mode choke measurement – length matters #2 which demonstrated that the following test fixture gave invalid results due to the 20mm length of resistor pigtails, the connection length in general terms Above is a pic of my experimental setup. The resistor on Port 1 is a 10k 1% metal film resistor. … Continue reading Common mode choke measurement – length matters #3

Common mode choke measurement – length matters #2

Following on from Common mode choke measurement – length matters… Lots of people have reported experiments to show gross failure of s11 reflection measurement of high impedances such as those encountered measuring common mode chokes. Above is a chart of a “10k resistor with leads” from (G4AKE 2020), the curve of interest is the s11 … Continue reading Common mode choke measurement – length matters #2

A prototype 50:75 RF transformer

The design is of a 50:75Ω autotransformer using a single Fair-rite 5943003801 (FT240-43) core. Note that this data is NOT for an Amidon #43 core. The winding is a total of 6t tapped at 5t, wound as two close wound layers. The prototype used a single conductor stripped from LAN cable. The winding configuration is … Continue reading A prototype 50:75 RF transformer

Dave Casler’s “why so little loss?”… a fact check!

Dave Casler sets out in his Youtube video to answer why two wire transmission line has so little loss . With more than 10,000 views, 705 likes, it is popular, it must be correct… or is it? He sets a bunch of limits to his analysis, excluding frequency and using lossless impedance transformation so that … Continue reading Dave Casler’s “why so little loss?”… a fact check!

Receive only antenna for 160m – matching and performance discussion – 8000pF?

A reader of Receive only antenna for 160m – matching and performance discussion referred me to an online discussion with a simpler solution. A couple of quotes from posters… It almost doesn’t matter what the actual receiver Zin is. What matters is the 100ft of 50 or 75 Ohm coax that is used to get … Continue reading Receive only antenna for 160m – matching and performance discussion – 8000pF?

Measurement of various loss quantities with a VNA – a worked example

This article documents a worked example of the matters discussed at Measurement of various loss quantities with a VNA. Above is an air cored solenoid of about 20µH connected between Port 1 and Port 2 of a NanoVNA-H4 which has been calibrated. The whole lot is sitting on an inflated HDPE bag to isolate the … Continue reading Measurement of various loss quantities with a VNA – a worked example

On testing two wire line loss with an analyser / VNA – part 6

Measuring velocity factor This article discusses measuring velocity factor using the NanoVNA. The DUT is coax with N type connectors as it provides a better example to demonstrate and learn from. Having acquired competency, extension to two wire lines is just a matter of attending to the matters of a suitable transformer, and appropriate SOL … Continue reading On testing two wire line loss with an analyser / VNA – part 6