Alexanderson-Day 2021

Today, another transmission by SAQ took place, celebrating this year’s Alexanderson Day:

Alexanderson Day 2021

Like many radio amateurs I too tried to receive the old lady once again, and was -somewhat- successful.

My portable setup was as following:

  • RX: Winradio G313e
  • high impendance preamp
  • 15m wire, about 1,5m over ground
  • Locator: JO42SI24

The preamp I built basically follows this schematic by DJ1WF, just that it doesn’t do any demodulation itself. Instead it has an output to the SDR where pin 7 of the TDA4100 would be connected. I was hoping to improve the sensitivity when using (too) short antennas, and while it doesn’t work as superbly as I was hoping for, it does improve the reception below 100 kHz by a good bit. Maybe it can be further optimised.

The reception wasn’t as good as I was hoping it to be, but a quick chat over the local UHF repeater unveiled that others had subpar reception as well, or didn’t hear SAQ at all when they could usually receive it. This, plus the fact that other stations in the VLF band were quite strong with my setup, indicates that it seems to work well enough and we just didn’t have much luck with the condx today.

I was using a 300 Hz filter, R was somewhere between 3 and 4. With a little patience and a good ear one could probably decode most of the message; I didn’t try yet.
As usual in the summer, there was a lot of QRN as well which didn’t make things easier. A noise blanker might have improved the audio quality, however I decided against it since I had no time left to tweak its settings and was afraid to actually worsen the outcome.

Here’s a losless recording of my reception. The actual message sent by SAQ starts around 1 minute in:

 

All in all I was happy with how it worked out even under the given conditions and had a nice afternoon. Here are some impressions from the reception site:

Hope to hear you again soon, dear SAQ!

Stratospährenballonstart von DL0PTB

Schon vor einer Woche ließen die Funkamateure der Physikalisch-Technischen Bundesanstalt in Braunschweig gleich zwei Wetterballons im Rahmen der virtuellen Ham Radio starten. Beide trugen Amateurfunk-Nutzlasten, einer von ihnen eine SSTV-Bake.

Stratosphären Ballonstart: 26.06.2021 – 12 Uhr MESZ

Da SSTV eine meiner Lieblings-Betriebsarten ist konnte ich mir die Chance zum Empfang natürlich nicht entgehen lassen. Aufgrund kurzer Vorlaufzeit diente der Georgengarten in Hannover als Empfangsstandort – mit dem Hintergedanken, dass ab einer gewissen Höhe des Ballons sowieso freie Sicht besteht, die Standortwahl also unkritisch ist.

Das Signal auf 145,200 MHz war gut zu empfangen, aber überraschend schwach. Angesichts der Sendeleistung von 100 mW und freier Sicht hatte ich mit kräftigeren Signalen gerechnet. Hier wäre eine Richtantenne zum Empfang wohl besser gewesen.

Zum Einsatz kamen mein FT-817 mit Aufsteckantenne sowie MMSSTV unter WINE. Derartige Live-Bilder zu empfangen hat schon einen besonderen Reiz, vor allem wenn man dabei zusehen kann wie Erdkrümmung und Atmosphäre immer deutlicher zu erkennen sind.

Bei etwa 31 km Höhe platzte der Ballon, kurz darauf setzten die SSTV-Aussendungen aus (Träger des Senders nach wie vor empfangbar, aber ohne Modulation).

Hier noch ein paar Impressionen:

Easily upgrading all OpenWRT packages

For some reason, opkg, the package manager of OpenWRT, has a function to list all upgradable packages, but none to upgrade them all – you need to type each one in by hand.

Or you do it like this:

#!/bin/ash
opkg update
opkg list-upgradable | cut -d " " -f 1 | xargs opkg upgrade

As usual, just paste the three lines of script above into a plain text file and make it executable with chmod u+x <filename>.

Hope this can help some people out there! 🙂