News archive December 2008 - Koos van den Hout

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2008-12-31 (#) 11 years ago
A complete scan at the highest point in the house gives me several more instances of Digitenne signals. As mentioned before, at 618 MHz Digitenne bouquet 1 with TV Noord-Holland, but also at 786 MHz and 826 MHz bouquet 2. These can come from a number of locations, I can only find out with a directional antenna. Due to the way several stations broadcast exactly the same program at the same frequency there is no way of knowing which station is transmitting it. The fact that the signals have to be exactly the same to avoid interference means there can be no identifying bits somewhere within the dvb datastream. I think it is way cool that transmitter technology is this far that we can transmit the same signal from different locations without interfering with eachother. It is probably the robustness against multipath interference that makes this possible: having more transmitters with the same signal is a form of multipath interference. DVB experiments page updated with these latest experiences.

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2008-12-30 (#) 11 years ago
In browsing some other stuff I found that FM / TV DX-ing is a genuine hobby for some people: trying to receive remote FM / TV stations using good antennas and using special receiving conditions when the signal gets scattered way beyond their normal reach. Thomas Tepe does this and reports about FM / TV receiving conditions on his blog (German). There even is a UKW/TV-Arbeitskreis interested in this subject in the German DX club. They publish complete overviews of transmitters in Germany, Austria, France, the Netherlands, Belgium, Luxembourg and Denmark (german). Their listing of the rtbf dvb-t bouquet matches my experiences with the Belgium Liege transmitter which is a nice plus for me.

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2008-12-30 (#) 11 years ago
Op 13 December had ik een bijzondere kans: als onderdeel van de afscheids activiteiten van vliegbasis Soesterberg organiseerde Vaarwel Vliegbasis Soesterberg een hardloopwedstrijd. Een vriend van ons ging hardlopen, en ik nam de unieke kans waar om eens te fotograferen op vliegbasis Soesterberg. Normaal natuurlijk zwaar verboden wegens militair terrein en actieve vliegbewegingen maar nu kon ik gewoon overal rondlopen met camera. Het was wel koud, en dat kwam goed hard aan op de open vlakte daar. Uiteindelijk een aantal mooie foto's kunnen maken: Startbaanrun 13 December 2008 Vliegbasis Soesterberg - Foto's Koos van den Hout

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2008-12-28 (#) 11 years ago
capture rtv-nh logo I tried w_scan again, this time in the highest possible place in the house where I can give the little antenna of the dvb-t stick an outside view. And suddenly 618 MHz is usable and gives me (among other services):
0x0000 0x0450: pmt_pid 0x0000 Digitenne -- TV Noord-Holland (running)
0x0000 0x0457: pmt_pid 0x0000 Digitenne -- Radio Noord-Holland (running)
Some bit errors, but usable signal.

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2008-12-28 (#) 11 years ago
Wardriving results 10 - 28 December: 2959 new networks with GPS locations. The box went along on a few cycling and car trips. I made number 16 in the WiGLE stats without seeing it coming: I was focused on getting 17th place again that I did not notice number 16 being somewhat close.

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2008-12-26 (#) 11 years ago
Christmas: time to visit the family in the south of the Netherlands, and a chance to scan the local tv-spectrum for valid DVB-T signals. German transmitters at 514 MHz: ZDF, 706 MHz: ARD and 602 MHz: ARD regional stations. Germany also seems to have a commercial DVB-T provider at 722 MHz offering several channels with some form of encryption. At 834 MHz I found the rtbf service from Walloon Belgium. It is nice to see how foreign DVB-T transmitters offer local channels.

In hopping between w_scan, scan and tzap to feed dvbsnoop data I found that w_scan leaves 'AUTO' in the channel list and in the generated channels.conf when not updated from the network information table. But, tzap can't parse 'AUTO' entries in channels.conf.

Looking at the network information tables with dvbsnoop shows interesting differences between countries. The Netherlands (Digitenne) shows alternate frequencies, Germany shows alternate frequencies with gps locations of transmitters (for mobile applications?) and Belgium admits you found rtbf.

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2008-12-24 (#) 11 years ago
Going further on the scanning for DVB-T channels I found w_scan, an automatic full-band scanner for DVB-T and DVB-C. The page is in German, but the application itself speaks enough English. This program finds all active DVB-T transmitters and fetches their network information table. On a test run in Utrecht I get:
# T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
T 498000000 8MHz AUTO AUTO AUTO AUTO AUTO AUTO
T 522000000 8MHz 2/3 1/2 QPSK 8k 1/4 NONE
T 618000000 8MHz AUTO AUTO AUTO AUTO AUTO AUTO
T 706000000 8MHz AUTO AUTO AUTO AUTO AUTO AUTO
T 762000000 8MHz AUTO AUTO AUTO AUTO AUTO AUTO
T 818000000 8MHz AUTO AUTO AUTO AUTO AUTO AUTO
During frequency scanning it even finds a transmitter at 618 MHz (UHF channel 39) but it can't find any valid data there. At 522 MHz (UHF channel 27) is the DVB-H service marketed as 'Mobile TV' in the Netherlands.

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2008-12-23 (#) 11 years ago
In geen jaren gezien: "Even geduld alstublieft" op televisie. Vanavond was er een storing op Nederland 1, 2 en 3. Berichtgeving: Korte storing bij televisiezenders (nos.nl), Korte storing bij televisiezenders. Screenshots: Nederland 2 Even Geduld Alstublieft, Nederland 3 Even geduld alstublieft. Handig, zo'n dvb-stick en de screenshots optie in mplayer.

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2008-12-23 (#) 11 years ago
I installed the Windows drivers and applications that Hauppauge included with the Nova-T stick to see what they 'know' about dvb-t reception. The application itself never showed what the DVB reception details are. I can see channel number or frequency, but nothing like modulation, guard rate, forward error correcting rate or pid. I eventually found out the WinTV application stores all channel data in a databasefile hcwChanDB_5.mdb but serious browsing of that file using mdbtools shows that the program IDs are listed but those settings aren't. I guess the DVB-T receiver in WinTV is really good at detecting those settings from the TPS (Transmission Parameters Signalling). The only things listed are the frequency and the service_id which is indeed the same as the service number which I can see using scan from dvb-utils.

Searching for the same functionality in Linux did not yield much until I browsed the linux-dvb mailinglist archives. I found that 'AUTO' is a valid setting for a lot of the values for scan. Trying that with the known frequencies does indeed give good results, so I can use that as an option when I can't find the right settings when scanning for German and Belgian dvb-t transmitters.


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2008-12-19 (#) 11 years ago
Google is doing more experiments with IPv6. They now offer the option to selected ISPs to return AAAA records for queries coming in via IPv6. XS4ALL being advanced and always interested in new technologies is participating in this program. But: you have to resolve completely via IPv6 to get an IPv6 address. So I fiddled a little with the setup of bind to use the XS4ALL ipv6 resolver for queries regarding google:
zone "google.com" {
    type forward;
    forward first;
    forwarders {
        2001:888:0:6::66;
        2001:888:0:9::99;
    };
};
And now I get the cool answer:
koos@greenblatt:~$ host www.google.com
www.google.com is an alias for www.l.google.com.
www.l.google.com has address 74.125.77.147
www.l.google.com has address 74.125.77.99
www.l.google.com has address 74.125.77.104
www.l.google.com has address 74.125.77.103
www.l.google.com has IPv6 address 2001:4860:0:1001::68
And the IPv6 instance of google will for example give me IPv6 cache links.

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2008-12-18 Continuing DVB scans 11 years ago
I found out why the two transmitters at 762 and 498 MHz weren't received correctly: I had the forward error correction rate wrong. And I guess scan from dvb-utils doesn't fetch those values from the network information table yet. Updating the table to the correct values:
# Digitenne (Utrecht / Maarssen / Lopik / Amersfoort, The Netherlands)
# T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
T 706000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE  # UHF 50
T 818000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE  # UHF 64
T 762000000 8MHz 2/3 NONE QAM64 8k 1/4 NONE  # UHF 57
T 498000000 8MHz 2/3 NONE QAM64 8k 1/4 NONE  # UHF 24
T 522000000 8MHz 2/3 NONE QPSK 8k 1/4 NONE   # DVB-H: UHF 27
Makes scan find everything, including the 'Mobile TV' services on the DVB-H frequency. DVB-H (Handheld) isn't that different from DVB-T I guess. I found the correct values after a good look at the Radio en TV zenders in Nederland site and its DVB-T and DVB-H listings.

This experience should help me understand scanning for German and Belgian transmitters when I try it in Limburg.

Update : tried it again with only listing the first transmitter, this has the weird effect that the other frequency with the same code rate (818 MHz) is always found and that 762 MHz is sometimes found and 498 MHz never on several tries. I guess scan does try to receive the network information table but does not receive it in full. With dvbshoop -nph 0x10 I do see a nice network table with several frequencies I saw scan try:
            DVB-DescriptorTag: 90 (0x5a)  [= terrestrial_delivery_system_descriptor]
            descriptor_length: 11 (0x0b)
            Center frequency: 0x03412140 (= 546000.000 kHz)
            Bandwidth: 0 (0x00)  [= 8 MHz]
            priority: 1 (0x01)  [= HP (high priority) or Non-hierarch.]
            Time_Slicing_indicator: 1 (0x01)  [= Time Slicing is not used.)]
            MPE-FEC_indicator: 1 (0x01)  [= MPE-FEC is not used.)]
            reserved_1: 3 (0x03)
            Constellation: 2 (0x02)  [= 64-QAM]
            Hierarchy information: 0 (0x00)  [= non-hierarchical (native interleaver)]
            Code_rate_HP_stream: 0 (0x00)  [= 1/2]
            Code_rate_LP_stream: 0 (0x00)  [= 1/2]
            Guard_interval: 3 (0x03)  [= 1/4]
            Transmission_mode: 1 (0x01)  [= 8k mode]
            Other_frequency_flag: 1 (0x01)
            reserved_2: 4294967295 (0xffffffff)

            DVB-DescriptorTag: 98 (0x62)  [= frequency_list_descriptor]
            descriptor_length: 33 (0x21)
            reserved_1: 63 (0x3f)
            coding_type: 3 (0x03)  [= terrestrial]
               Centre_frequency: 0334ec40  (= 538000.000 kHz)
               Centre_frequency: 0371f540  (= 578000.000 kHz)
               Centre_frequency: 03f83c40  (= 666000.000 kHz)
               Centre_frequency: 041cdb40  (= 690000.000 kHz)
               Centre_frequency: 04724e40  (= 746000.000 kHz)
               Centre_frequency: 04af5740  (= 786000.000 kHz)
               Centre_frequency: 04e02b40  (= 818000.000 kHz)
               Centre_frequency: 04ec6040  (= 826000.000 kHz)
Hmm, here are the frequencies I missed:
            DVB-DescriptorTag: 90 (0x5a)  [= terrestrial_delivery_system_descriptor]
            descriptor_length: 11 (0x0b)
            Center frequency: 0x02ebae40 (= 490000.000 kHz)
            Bandwidth: 0 (0x00)  [= 8 MHz]
            priority: 1 (0x01)  [= HP (high priority) or Non-hierarch.]
            Time_Slicing_indicator: 1 (0x01)  [= Time Slicing is not used.)]
            MPE-FEC_indicator: 1 (0x01)  [= MPE-FEC is not used.)]
            reserved_1: 3 (0x03)
            Constellation: 2 (0x02)  [= 64-QAM]
            Hierarchy information: 0 (0x00)  [= non-hierarchical (native interleaver)]
            Code_rate_HP_stream: 1 (0x01)  [= 2/3]
            Code_rate_LP_stream: 0 (0x00)  [= 1/2]
            Guard_interval: 3 (0x03)  [= 1/4]
            Transmission_mode: 1 (0x01)  [= 8k mode]
            Other_frequency_flag: 1 (0x01)
            reserved_2: 4294967295 (0xffffffff)

            DVB-DescriptorTag: 98 (0x62)  [= frequency_list_descriptor]
            descriptor_length: 33 (0x21)
            reserved_1: 63 (0x3f)
            coding_type: 3 (0x03)  [= terrestrial]
               Centre_frequency: 02f7e340  (= 498000.000 kHz)
               Centre_frequency: 0334ec40  (= 538000.000 kHz)
               Centre_frequency: 034d5640  (= 554000.000 kHz)
               Centre_frequency: 0371f540  (= 578000.000 kHz)
               Centre_frequency: 03969440  (= 602000.000 kHz)
               Centre_frequency: 04661940  (= 738000.000 kHz)
               Centre_frequency: 048ab840  (= 762000.000 kHz)
               Centre_frequency: 0496ed40  (= 770000.000 kHz)
But: it takes a while before I see these. Maybe scan is a bit impatient and misses bits of the network information table in this specific case. This is all very theoretical as these frequencies only have scrambled services anyway. But I was too curious why this wasn't working as expected.

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2008-12-16 (#) 11 years ago
Bits! Image! Sound! .. the dvb-t stick works. Really plug and play, I just plugged it in and Ubuntu Linux recognized it and loaded the correct driver. To start the tuning process I had to give it an initial frequency and settings which I stored in /usr/share/doc/dvb-utils/examples/scan/dvb-t/nl-Utrecht:
# Digitenne (Utrecht / Maarssen / Lopik / Amersfoort, The Netherlands)
# T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
T 706000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE
That's enough to start the tuning process, the rest of the frequencies is found automatically:
initial transponder 706000000 0 1 9 3 1 3 0
>>> tune to: 706000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_1_2:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_4:HIERARCHY_NONE
Network Name 'Digitenne'
0x0000 0x044d: pmt_pid 0x1b62 Digitenne -- Nederland 1 (running)
0x0000 0x044e: pmt_pid 0x1b6c Digitenne -- Nederland 2 (running)
.. somehow it knows the other frequencies and keeps on going:
retrying with f=818000000
>>> tune to: 818000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_1_2:FEC_1_2:QAM_64:TRA
NSMISSION_MODE_8K:GUARD_INTERVAL_1_4:HIERARCHY_NONE (tuning failed)
0x08a3 0x000b: pmt_pid 0x03f2 Digitenne -- RTL 4 (running, scrambled)
0x08a3 0x000c: pmt_pid 0x03fc Digitenne -- RTL 5 (running, scrambled)
Eventually finding 38 services. When I set up /usr/share/doc/dvb-utils/examples/scan/dvb-t/nl-Utrecht with all the known transmitters, like
# Digitenne (Utrecht / Maarssen / Lopik / Amersfoort, The Netherlands)
# T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
T 706000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE
T 818000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE
T 762000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE
T 498000000 8MHz 1/2 NONE QAM64 8k 1/4 NONE
It still finds nothing on 498 MHz, strangely enough. I don't get 'tuning failed' but I do get errors from the pid filters.
The only thing failing at the moment is the remote: I can't find the right settings for lirc yet. But I haven't tried very hard.

Anyway: digital TV. It works!
Minor update: I learned using dvbsnoop that the 'somehow it knows the other frequencies' comes from the fact that the list of frequencies is included in the DVB standard as the Network Information Table (NIT).
Update 2008-12-18: I found the error correcting rates for two transmitters were wrong, fixed in the DVB experiments page.


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2008-12-14 (#) 11 years ago
Recently my interest in digital video broadcasting was tickled, so I started reading about it again. With television I usually have this 'the technical side is interesting but the content is not interesting' opinion so I am not going to buy a satellite dish at home yet. My ideas on what I want to play with and where are now documented at my DVB experiments page. I did order a simple free-to-air capable dvb-t usb stick so I can play with it. When I get bored with the subject again it's still a way to get some TV news should the cable fail or on the road.

Making those maps for the DVB experiments page was quite a bit more work than expected. I hoped to simply use openstreetmap maps and put some extra points in those but that was harder than expected. I tried gpsdrive but it can't just download openstreetmap street maps. It does have some openstreetmap support but if I get it correctly I'll have to install the whole mapnik program suite first. I skipped that for now. What I did was download maps from openstreetmap using gpsmap from kismet and import those in gpsdrive. Well, the gpsdrive import did not work correctly but I just put the right numbers in map_koord.txt. The waypoints for the transmitters al came from the German Bundesnetzagentur. Being very German and therefore very gründlich (thorough): they list all the active DVB transmitters for all surrounding countries, even where the chance of actual interference is quite small, like Den Burg on Texel in the Netherlands or Viborg in Denmark. With the maps with the transmitters as waypoints shown in gpsdrive I made some screenshots used on the page, with some lightbox 2 sprinkled on top for nice viewing.


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2008-12-10 (#) 11 years ago
New record in ntp.cs.uu.nl traffic: 2429 packets/second of ntp traffic. At that level the server does seem to miss some traffic: according to the pool.ntp.org: Stats for 131.211.84.189 it missed one request from the monitoring system completely, which drops the score several points at once.

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2008-12-10 (#) 11 years ago
Wardriving results 5 - 9 December: 2311 new networks with GPS locations. I'm back at number 17 in the WiGLE stats. Not many days but a few long rides happened in those days and an error in uploading making the oldest results nearly scrolling away from the upload stats.

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2008-12-09 (#) 11 years ago
New weirdness in the system logs: dns queries for names that resolve to nearby IP addresses. At home, an xs4all IP:
Dec  7 08:51:34 gosper named[877]: denied query from [79.111.252.228].4233 for "luna.vulcan.nu" A/IN
Dec  7 08:51:34 gosper named[877]: denied query from [79.111.252.228].4235 for "zuul.xs4all.nl" A/IN
Dec  9 11:42:11 gosper named[877]: denied query from [212.46.197.83].54183 for "luna.vulcan.nu" A/IN
Dec  9 11:42:11 gosper named[877]: denied query from [212.46.197.83].54187 for "zuul.xs4all.nl" A/IN
Both names resolve to xs4all IPs in the same block as my home IP. On a resolver at work:
Dec 09 19:31:01.372 security: info: client 208.37.177.62#46262: query(cache) 'ns.uu.nl/IN' denied
Dec 09 19:45:57.494 security: info: client 204.11.51.61#43318: query(cache) 'ns.uu.nl/IN' denied
either coincidence or signs of some form of searching for security holes. In todays Internet I always assume the latter.

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2008-12-09 (#) 11 years ago
Ik was aan het zoeken naar informatie over en aanbieders van een 'voet' om een satelliet ontvangst schotel op een plat dak te kunnen plaatsen. Niet voor thuis, maar omdat er voor een onderzoeks project op het werk vraag is naar een satelliet schotel.
Opvallend is hoe ik veel en veel meer informatie vind over gemeentes die een Mening hebben over satellietschotels dan over aanbieders van spullen om het goed te doen. Er is een enorme aversie tegen schotelantennes in het straatbeeld. Eigenlijk zijn een beetje de jaren 70 terug toen gemeentes bepaalden dat hun kabelnet de antennes op het dak overbodig maakten, nu willen gemeentes geen schotelantennes in het straatbeeld. De genoemde reden is altijd dat het er slecht uitziet maar het gaat volgens mij om de associatie met bepaalde bevolkingsgroepen (alleen dat noemen is discriminatie, dus gemeentes doen iets aan het symptoom schotelantenne).

Mijn persoonlijke visie is dat de vrijheid van informatievergaring een veel belangrijker grondrecht is dan de wens om niet tegen zaken aan te kijken die niet bevallen. Gelukkig is het Europese verdrag van de rechten van de mens het met me eens en wordt dit nogal eens gebruikt om al te strenge regels of zelfs belastingen op schotelantennes aan te vechten, op zowel 'vrijheid van informatiegaring' als 'vrij verkeer van diensten'.

Op onze vakantie in Denemarken viel het me op hoe normaal schotelantennes daar zijn, ook in gebieden waar kabel een alternatief was. Dat had niets te maken met bepaalde bevolkingsgroepen maar gewoon met de wens meer of andere keuze te hebben aan televisie-content dan geboden via de ether of kabelnet.

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2008-12-09 (#) 11 years ago
Geinspireerd door de zeer uitgebreide collectie bij de UK broadcast transmission gallery heb ik besloten zelf ook wat foto's die ik gemaakt heb van broadcast zenders publiek on-line te zetten. Gelijk is dan ook de uitdaging om meer van deze masten te fotograferen en goeie foto's er van beschikbaar te maken.
Mijn foto's van zendmasten.

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2008-12-05 (#) 11 years ago
Wardriving results 7 November - 4 December: 591 new networks with GPS locations. Still at 18 in the WiGLE stats although I am slowly creeping up on number 17.

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2008-12-03 (#) 11 years ago
Bij een opruimactie kwam ik een doos tegen met 'BBS' er op. Veel papier er in wat toch echt wegkon (rekeningen van walnut creek cdrom). Uitgeprinte mailtjes van wilde ideeën voor het BBS zoals een fax naar Amerika gateway. Maar het mooiste was wel de kerstkaart die we voor het BBS gemaakt hebben in December 1993. Die bewaar ik wel, en de kaart is nu ook on-line te bewonderen. Natuurlijk is de geschiedenis van BBS Koos z'n Doos bijgewerkt met de nieuwe feiten die ik kon halen uit dingen die ik tegen kwam.

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2008-12-02 (#) 11 years ago
Something that got my attention recently: the Dundee satellite receiving station offers access to weather satellite images. Using big dish antennas you can follow via webcam high-resolution images are captured from the weather satellites. The free images are relatively low-resolution (still filling the screen) but it is a nice enough resolution to get a view of the weather over Europe and see low-pressure areas develop.

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2008-12-01 (#) 11 years ago
Stuff computers are better at: shutting down at the wanted time. Just a simple:
root@hostname:~# at 23:01
warning: commands will be executed using /bin/sh
at> shutdown -h now
at> <EOT>
job 3 at Mon Dec  1 23:01:00 2008
root@hostname:~# 
The <EOT> was were I pressed ctrl-d. You might say "why not shutdown -h 23:01 ?". Well, your users will be bothered by the announcements between now and the shutdown time.

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, reachable as koos+website@idefix.net. PGP encrypted e-mail preferred.

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