Continuing DVB scans / 2008-12-18

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.

Tags: ,

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

PGP key 5BA9 368B E6F3 34E4 local copy PGP key 5BA9 368B E6F3 34E4 via keyservers pgp key statistics for 0x5BA9368BE6F334E4 Koos van den Hout
RSS
Other webprojects: Camp Wireless, wireless Internet access at campsites, The Virtual Bookcase, book reviews
This page generated in 0.004199 seconds.