News archive January 2014 - Koos van den Hout

Mooie tekst van Arnoud Engelfriet op Wat nou als jailbreaken mijn telefoon juist veiliger maakt? - Ius Mentis:

Overigens erger ik me wezenloos aan de trend om dienstverlening ‘producten’ te noemen. Een product doet pijn als het op je tenen valt. Mobiel Bankieren (of gratis reizen buiten de spits) doet dat niet, dus is het geen product.

Een mooi verhaal over een enthousiaste jonge beginnende radio amateur die met wat hulp mooie dingen aan het doen is: PI4RCG sponsort Lithouwse novice zendamateur LY5AT, door PA3FYM.

Terug van een snowboard vakantie in Fiss, Oostenrijk! Perfect weer gehad, zowel met zon als met verse sneeuw.

I had a look what software is available for predicting satellite passes in the ubuntu ham radio software repositories.

predict-g1yyh in an xterm

I found PREDICT satellite tracking and orbital prediction program which does all the calculations given recent Keplerian elements which are available from sources like Keplerian elements at Amsat and Current NORAD Two-Line Element Sets at celestrak. Predict comes in two versions: predict in a version from May 2006 and predict-g1yyh. They look a bit different but the calculations are the same in the end.

Important part (to me) is the software also does the calculations for doppler shift. Doppler shift does occur measurably in radio signals when the two stations have a high enough speed difference between them. Since amateur radio satellites are low earth orbit satellites, the speed is measured in kilometers per second and the shift is there and should be taken into account. Shifts in the 70cm band are high enough that you need to retune the radio. As visible in the screenshot predict does calculate the frequencies when the satellite is visible.

gsat graphical client for predict screenshot

The interesting part is that predict and predict-g1yyh can also run as a server program where clients can access the data. One of the interesting clients is gsat from package predict-gsat. With gsat a world map is plotted with the home location and the satellite footprint visible and the data for antenna direction and doppler shift is shown.

gpredict screenshot main window

I also found package gpredict which is totally not related to predict. In my opinion gpredict has a more modern interface (it's gtk+ based) but it lacks support for doppler shift. This makes it somewhat less interesting for radio use.

gpredict screenshot radio control with doppler shift.

Update: gpredict can support doppler shift when it thinks it can control a radio. Configuring a radio with RX only support will make the 'Radio Control' window available where you can select the satellite and its services when it is known to gpredict under 'Target' or enter the uplink and downlink frequencies of the satellite by hand, select 'track' and see the result of the doppler shift calculations.

I wanted to experiment a bit with rtl_tcp on ritchie which has linux kernel 3.12, and after inserting the stick I noticed the following in the syslog:

[405465.908104] usb 1-3: new high-speed USB device number 2 using ehci-pci
[405466.052247] usb 1-3: New USB device found, idVendor=0bda, idProduct=2838
[405466.052274] usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[405466.052293] usb 1-3: Product: RTL2838UHIDIR
[405466.052310] usb 1-3: Manufacturer: Realtek
[405466.052328] usb 1-3: SerialNumber: 00000001
[405466.217234] usb 1-3: dvb_usb_v2: found a 'Realtek RTL2832U reference design' in warm state
[405466.285098] usb 1-3: dvb_usb_v2: will pass the complete MPEG2 transport stream to the software demuxer
[405466.285208] DVB: registering new adapter (Realtek RTL2832U reference design)
[405466.348588] usb 1-3: DVB: registering adapter 0 frontend 0 (Realtek RTL2832 (DVB-T))...
[405466.378308] r820t 0-001a: creating new instance
[405466.390283] r820t 0-001a: Rafael Micro r820t successfully identified
[405466.397306] Registered IR keymap rc-empty
[405466.397785] input: Realtek RTL2832U reference design as /devices/pci0000:00/0000:00:0f.5/usb1/1-3/rc/rc0/input5
[405466.404262] rc0: Realtek RTL2832U reference design as /devices/pci0000:00/0000:00:0f.5/usb1/1-3/rc/rc0
[405466.449642] IR NEC protocol handler initialized
[405466.453552] IR RC5(x) protocol handler initialized
[405466.459768] IR RC6 protocol handler initialized
[405466.470835] usb 1-3: dvb_usb_v2: schedule remote query interval to 400 msecs
[405466.471385] IR JVC protocol handler initialized
[405466.474504] IR Sony protocol handler initialized
[405466.481423] IR SANYO protocol handler initialized
[405466.483311] usb 1-3: dvb_usb_v2: 'Realtek RTL2832U reference design' successfully initialized and connected
[405466.483477] usbcore: registered new interface driver dvb_usb_rtl28xxu
[405466.493045] input: MCE IR Keyboard/Mouse (dvb_usb_rtl28xxu) as /devices/virtual/input/input6
[405466.498074] IR MCE Keyboard/mouse protocol handler initialized
[405466.501562] lirc_dev: IR Remote Control driver registered, major 251 
[405466.510997] rc rc0: lirc_dev: driver ir-lirc-codec (dvb_usb_rtl28xxu) registered at minor = 0
[405466.511017] IR LIRC bridge handler initialized

It has valid drivers as dvb-t receiver and ir receiver now! That's not what I wanted, I want raw usb access for rtl_tcp. Time to blacklist certain modules:

blacklist dvb_usb_rtl28xxu
blacklist rtl2830
blacklist rtl2832
blacklist lirc_dev

And now no drivers get loaded and rtl_tcp has raw usb access again after updating the udev rules.

No success with gqrx using a remote rtl_tcp: audio was stuttering and frequency changes were visible in rtl_tcp but didn't really happen, there was a huge lag. Traffic between the system running rtl_tcp and gqrx was going over a wireless network, a linux router and a wired network. Bandwidth was not a problem.

I was considering running one rtl-sdr stick with the HF convertor in the shed so it would have less interference but that doesn't seem feasible at the moment.

Vandaag moest ik wat dingen met de auto doen. Daarmee kon ook de porto mee met de raamantenne aan de buitenkant van de auto. Dat werkte prima, PI3UTR was prima te volgen en een QSO maken lukte ook zonder problemen. Met dezelfde porto en hetzelfde vermogen waarmee ik op de ligfiets er maar moeilijk overheen kom lukte het met een net iets hogere antenne die zeker rechtop zit prima.

I use fvwm2 as window manager on an ubuntu system. This means that applications that use the gnome style libraries run fine, but it can be a bit harder to find the settings. I was playing with pavucontrol (another gnome app) when I noticed the setting 'system sounds volume' made the boingo noises come back when a window popped up such as a thunderbird password window or an gnome-ssh-askpass window. The definitive solution is to start gnome-conf-editor and disable boolean /desktop/gnome/sounds/event/sound/event_sounds. Silence again. Sound can be nice when playing music or viewing video but I don't want a sound every time I have to type a password/passphrase.

Uit de mail:

Dat u de inhoud van deze nieuwsbrief niet direct kunt lezen komt wellicht door de instellingen van uw browser.

Browser? Welke browser? Er is geen browser. Dit is een e-mail bericht, en ik kijk er naar met mutt.

Searching for the print header - COM port cable in the PC parts junk box for the new weatherstation on the alix.1c board gave 5 of them, 2 with db9 connectors and 3 with db25 connectors. I tested them all with a real telephone modem. In total 3 worked, 2 didn't but that may be because there are two different standards for it.

Wardriving results 3 May 2013 - 3 January 2014: 14554 new networks with GPS locations. All wardriving in this period using the WigleWifi app for Android.

Current todo list new weatherstation installation on ritchie:

• Set up udev rules for libusb access by non-root user so w1retap can run. Done, via a w1retap group. ✓
• Get w1retap to run on the system. Done ✓
• Get backups running using the amanda system. Done ✓
• Add serial cable from alix1c COM2 header to outside. I found out that there are two types of cables for this and the "Intel" version won't work. So if the PC parts junkbox has these cables they still need to be tested. Done ✓
• Get the conrad serial port weather station running on that port. Done ✓

That should get things moving to a level comparable to the current setup.

And the wishlist for improvements:

• Something to put the system in so it is in a good place in the shed and somewhat shielded from temperature/humidity influences.
• System statistics gathered. Wishlist: cpu load and states, processes, temperatures and voltages mainboard, temperature disk, entropy, ntp stats. ✓
• Logging done in a way data will be on the home server and interruptions of the network link will be handled. I'm starting to use the term telemetry to describe this process of gathering timestamped data, preparing it for transmission over maybe flaky network links and processing it on the server. Partly done, some data is still gathered in the 'old' style.
• A working gps receiver so it can work as a standalone time server.
• Get the rain meter of the conrad weather station set up.
• Get the wind speed meter (anemometer) of the conrad weather station set up.
• Get the wind direction meter set up.
• Upload the available weather information to the CWOP (citizen weather observatory program) using APRS-IS.

Ik was vandaag op de heuvel Hettenheuvel in het Bergherbosch bij Braamt. Ik had de porto mee en op een kant van de heuvel met zicht naar het westen probeerde ik PI3UTR te ontvangen wat lukte. Niet storingsvrij maar duidelijk genoeg om de callgever te verstaan (Q3). De repeater openen lukte niet met de 5W porto. Volgens het hoogtebestand Nederland is de hoogte daar 70 tot 90 meter.

Ik heb daarna eens aan deze link gerekend in Radio Mobile online en gezien dat van PI3UTR naar deze locatie line-of-sight precies door de bomen van de heuvelrug gaat. De afstand was dus iets meer dan 81 kilometer.

Dit geeft wel aan waarom deze repeaterfrequentie gecoördineerd moet worden met Duitsland: het Bergherbosch is nog net niet in Duitsland, maar het scheelt weinig. Op een hoge locatie aan de andere kant van de grens of bij condities zal deze zeker te ontvangen zijn.