14 April, 2021

Learning the hard way that plastic TO-92 is affected by humidity

I've had my APRS temperature station running since 2012. It is based on a DS18S20 sensor that just sticks out of a window. However, after some time it started to give too high readings, and after having replaced it several times I found out that I needed to waterproof it better. It seems that the TO-92 plastic housing, shown here to the right, somehow was influenced by humidity.

I wasn't able to find waterproofed DS18S20 sensors, but I could find ones with DS18B20. I got one and connected it, but it only showed -1 C regardless of weather. The software in the Opentracker USB was not able to read it, although I have Arduino programs that can read both.

07 April, 2021

Now active via the International Space Station

I happened to set my 2m receiver to the APRS (Automatic Packet Reporting System) frequency of the International Space Station (ISS), 145.825 MHz, and lo and behold stations in Central and Southern Europe started to appear. This is not rocket science, but for me it's a first. (Well actually the ISS is a kind of rocket ...)

Here in Oslo, using the local APRS service, I can also receive Swedish and Danish stations when conditions are good, but never Spain, Italy, Greece, Romania, Ukraine, Russia or Turkey. When a message appeared from NA1SS itself, the station onboard the ISS, I felt that I had really nailed it (see image). But ISS had more in store for me.

03 March, 2021

QRPLabs 25 MHz TCXO performing well in the U3S

I have tried several oscillators in the U3S QRSS/WSPR transmitter from QRPLabs. First an analog devices DDS, then a Silicon Labs oscillator chip running from an ordinary 27 MHz crystal, and then QRPLabs own oven controlled oscillator. I thought I had managed to control the drift when I got the oven controlled oscillator. But then after a while it started drifting again. I didn't want to go through its rather cumbersome calibration procedure once more so I gave it up recently when the TCXO module became available. This tiny module is shown in the first image.

23 January, 2021

Eleven and 87 year sunspot cycles

It is well known that the sunspots vary over an eleven-year cycle. As the sunspot number increases, the ionosphere is more ionized and radio propagation on the high shortwave bands from about 10 - 30 MHz. Also, the higher the sunspot number, the more likely is the appearance of Northern Lights.

Here's spectral analysis of the monthly sunspot numbers from 1750-2020. First I show Fourier based spectrogram analysis. The y-axis is frequency or inverse years and there are arrows marking 11 years as well as the Gleissberg cycle of about 87 years. Note how the 11 year cycle has split into two periods since the 50's. There is a weak subharmonic at 5.5 years also. Due to the 90 year analysis window length, the time scale ends 45 years before 2020, i.e. in 1975.