Chinese AD8307 power measurement module #4

Desk study of opportunity to improve linearity. At Chinese AD8307 power measurement module #2 I showed measurement of the linearity of an AD8307 based RF power meter. The specification linearity is +/-1dB, which is poorer than one might like in a power measuring instrument. The diagram above from the AD8307 datasheet shows the internal architecture, including … Continue reading Chinese AD8307 power measurement module #4

Chinese AD8307 power measurement module #3

At Chinese AD8307 power measurement module #2 I concluded that the modified AD8307 was useful on HF, and through to 54MHz depending on accuracy requirements. This article looks at combining the AD8307 module with a display option based on an Arduino Nano. Above is a demonstration of the display prototype. The module in the foreground … Continue reading Chinese AD8307 power measurement module #3

Chinese AD8307 power measurement module #2

At Chinese AD8307 power measurement module #1 I documented the first phase of checkout of a low cost AD8307 module. There are two requirements for accurate power measurement: input impedance of the power meter must be very close to 50+j0Ω (say input VSWR<1.2); and then gain from the SMA terminals to the AD8307 input terminals … Continue reading Chinese AD8307 power measurement module #2

VU3SQM directional wattmeter build – #2

VU3SQM directional wattmeter build – #1 laid out the first steps in design review and build of a directional wattmeter. This article canvasses the issues of the display. Intention is a digital based display (though not to exclude an analogue meter or bar graph type displays). So, the output of the AD8307 needs to be … Continue reading VU3SQM directional wattmeter build – #2

VU3SQM directional wattmeter build – #1

VU3SQM offers an interesting directional coupler based on a Sontheimer coupler, and using AD8307 power sensing for a nominally HF coupler. I must say that I am not a fan of Sontheimer couplers… but that is what the board uses. This article lays out a preliminary design review to assist in selection of appropriate toroids, … Continue reading VU3SQM directional wattmeter build – #1

RFPM2 – calibration files

The RF Power Meter 2 (RFPM2) stores calibration constants in a file located in the (SPIFFS) file system in the microcontroller flash. The file opened by default when RFPM2 starts is /default.cfg, the following is an example. { “name”:”dBm”, “hostname”:”rfpm201″, “vref”:3.3, “avg”:3, “slope”:0.12991, “intercept”:-91.406, “unit”:”dBm”, “lcdfsd”:16 } The parameters above capture the most basic operation … Continue reading RFPM2 – calibration files

Time to get some experience with 32bit microcontrollers – some progress

At Time to get some experience with 32bit microcontrollers I wrote that after almost 50 years working with 8bit microcomputers and microcontrollers, I thought it about time to get my hands dirty on some 32bit microcontrollers. This article reports some work in the STM stream. I abondoned the ST Discovery board in favour of a … Continue reading Time to get some experience with 32bit microcontrollers – some progress