Trip to HK & CN 2014 – Part 5: RTL-SDR, More Radio, AIS & Night Photos

It’s been a while since the trip, but I’ve been just way too busy lately to post anything more about the experiments and photos I’ve taken during my trip. The trip continues, with this part focusing mostly on more radio related goodness from the comfort of the hotel room and some night shots from nearby.

DTMB Broadcasts

In an earlier part, I did make a full analysis of the on-air DMB-T transmissions offered in Hong Kong, using a small thin stick-aerial. The analysis was done based on captured TS files, although I did actually start with the included Arcsoft software. The Arcsoft software did allow for display of Chinese characters, so the Chinese channel names and LCNs were shown instead of the English ones in the SDT.

tv station1 tv station2 tv station3

DAB+ Broadcasts

So lets look at something I didn’t look at in the previous parts – digital radio. One of the best things about having the local-TV-tuner dongle is that it also supports receiving DAB+ via the Magic Radio application.

In Hong Kong, digital radio is done by DAB+ in the VHF band, almost identically to Australia. There were a total of 17 DAB+ stations available when I was there, as shown by the scan results:

dabplus1 dabplus2

It seems there are only limited numbers of digital radio operators – mainly URadio, Digital Broadcasting Corporation (DBC), Radio and Television Hong Kong (RTHK) and Metro Broadcast Corporation (M). Interesting, all the stations were broadcast from one multiplex, whereas in Sydney, we have three. The multipath selective fading was clearly shown when looking at the carrier in SDR# from my RTL-SDR, making a very interesting “arty” pattern. The dips in the signal are quite significant – often 20dB down, so the error correction did a great job of keeping everything “listenable”.

DABplus-carrier1

I’ve never had any DAB+ receiver which was capable of more than just audio reception and basic text display, but in Hong Kong, it seems that many of the DAB stations also use the slideshow feature and broadcast still images of station logos, and news-headline images. This uses the spare bandwidth capacity of the DAB+ carrier to carry the images. Sometimes they do come out corrupted, but I doubt many of the DAB+ receivers will make such images available to the end users.

Some station logos caught include:

dab-rthkr3 rthk5 uradio3 uradio

uradio2 mradio mldigital dbc2main

Interestingly, it seemed that RTHK also suffered a broadcast failure, so they broadcasted an apology in their slideshow as well, which I managed to catch.

rthk3-failure

AM and FM Broadcast

As you can tell from above, I did bring along my RTL-SDR dongles to get a bit of a view of the radio spectrum. But that wasn’t all. I carried along a conventional Degen DE1103 AM/FM/SW radio as well, just to make sure I could access the lower bands should the need arise. The Degen DE1103 is a fantastic receiver for the size and for the price, with the most sensitive WFM and SW performance I have seen in a compact. It comes with a stupid keypad, and a needless LCD, but has a excellently long telescopic antenna, a BFO for SSB reception and external antenna jack. The best part is that, with a keyboard hack, you can also get LW reception as well.

The first thing I did was to try and scan around the AM band for some transmissions. My expectation was not to find any, because it’s a fairly old transmission method. To my surprise, there were a few. The listing below is in khz, and may be off by 1-2khz.

569, 620, 676, 748, 785, 864, 1061, 1215, 1289

The FM band, however, is the big surprise. The FM band was crowded beyond belief. On a sensitive radio like the DE1103, the band is frustrating because of the sheer number of stations received, in Mhz. The values might be off by 0.1-0.2Mhz because of the FM capture effect.

87.4, 87.5, 87.7, 88.1, 88.3, 88.5, 88.9, 89.2, 89.5, 89.8, 90.1,
90.3, 90.7, 90.9, 91.1, 91.4, 91.8, 92.1, 92.5, 92.9, 93.3, 93.9,
94.2, 94.4, 94.8, 95.2, 95.6, 95.8, 96.0, 96.3, 96.9, 97.1, 97.5,
97.9, 98.1, 98.4, 98.7, 98.9, 99.1, 99.3, 99.7, 100.2, 100.5, 100.8
100.9, 101.1, 101.4, 101.5, 101.8, 102.0, 102.4, 102.5, 104.0,
104.3, 104.5, 104.9, 105.2, 105.5, 105.7, 106.2, 107.0, 107.5,
107.7

The scan results, represented on a number line, with dots spaced 200khz, 250khz and 300khz illustrates just how closely spaced the stations are.

FM-station-spacing

A scan using Magic Radio shows only the strongest stations due to the lower sensitivity.

fm1

fm2

fm3

Overall, the FM broadcast band in Hong Kong is just way too crowded. This doesn’t help because of its proximity to Shenzhen, China, which is probably broadcasting its own FM stations to its own band plan, spilling over into Hong Kong. The audio quality in general is very distorted on many stations, with stereo lock being lost frequently on loud portions, and adjacent channels sometimes being captured.

Part of the reason is due to the challenging terrain, which results in the need to put in many repeater stations to fill-in. These repeaters operate on a separate frequency, using up precious spectrum. As a result, tuning across the band, it is possible to find six copies of the same program simulcast, each with different levels of interference and signal strength.

Interestingly, there are quite a few English-based services on the air, and it was possible to hear a lot of songs you would hear on Aussie radio. I felt “at home” in a sense.

It seems the quality of service is quite poor even for stationary listening, unlike in Sydney, where the signals are less crowded and generally “clean”.

A check of the spectrum using the RTL-SDR did turn up some very unusual spectrum behaviour – selective frequency fading which may be a result of co-channel broadcasting, multipath or something else entirely. There are also cases of spattering across on adjacent channels, non-symmetrical signals.

sz878 noisyclassica 976 rthk1 944 cr1-895 overmod mfinance 1040

Decoding RDS from the transmissions was very much a mixed bag due to the unusual FM carrier characteristics noted in the above shots.

I did try for shortwave services, but the mass of local QRM from switching power converters, energy saving lamps etc swamped out any hope of being able to receive it with anything short of a shielded loop antenna, so I gave up.

Other Radio Transmissions

Of course, there’s a lot more to radio than just broadcast. I didn’t have that much time, but I did a rough scouring of the bands and came up with a very rough (and uncertain) band-plan:

69 - 80Mhz - NFM Voice
87.8 - 108Mhz - WFM Broadcast
108 - 136Mhz - Aviation Band
136 - 156Mhz - NFM Voice
156 - 162Mhz - Marine Band
162 - 172Mhz - >?<
172 - 173Mhz - POCSAG Pagers
173 - 279Mhz - Analog TV >?<
279 - 280Mhz - POCSAG Pagers
280 - 396Mhz - Analog TV >?<
396 - 430Mhz - Digital Voice (TETRA)
430 - 852Mhz - Digital TV >?<
852 - ???Mhz - Digital Voice (TETRA, GSM)

Interesting points include the use of the below-FM broadcast band for narrowband FM voice services, which is not that commonly used here in Australia anymore. The long antennas and limited transceiver choices are just some of the reasons why it’s not common to see it anymore.

I did manage to catch two ATIS services, one for arrival, and one general and the Hong Kong ATIS shares an unusual characteristic of dropping the carrier in-between loops.

HKATIS-loopdown hkarrivalatis

POCSAG pagers are still on the air, which is pretty interesting too given the antique-status of the technology topping out at 2400bps.

pocsag2400-idle

The 400Mhz band has already moved over entirely to digital voice technology, utilizing TETRA standard which is encrypted. We are only just in the throes of moving over to more spectrally-efficient transmission modes, such as APCO P25, DMR/NXDN, MotoTRBO, etc.

Marine AIS Transmissions

I have always meant to receive marine AIS transmissions. You can think of this like an ADSB, but for boats instead of aircraft. Unfortunately, I’m not close enough to the water in Sydney to be able to receive them, so I’ve never actually been able to do it.

With a harbour-view room, I had no excuse not to try to receive AIS. I was able to use OpenCPN, AISMon, SDR#, and Virtual Audio Cable together to make a working, although crude, AIS system. For the record, I did try to receive ADSB as well, but unfortunately, without a clear view of the sky, there wasn’t much action on the screen.

SDRsharpais-inaction

The first step is to tune into the AIS frequency in NFM mode using SDR# and the RTL2832U. Unfortunately, there are two frequencies for AIS, and the best reception uses both of them. I only had equipment for one, so I stayed with just one frequency. As transmissions are done on alternate frequencies to avoid jamming, this means the AIS display will be slower to build and more likely to miss an update here or there.

The audio, unfiltered, is piped through the Virtual Audio Cable into the free decoder, AISMon.

aismon-setup

AISMon seems to like having a serial output, so on a laptop without a serial port, it does throw an error but continues to work correctly. Unfortunately, outputting to a LogFile doesn’t seem to work and causes the application to crash. UDP output is used to link this to the plotting software, OpenCPN.

busyharbour2

I didn’t bother working out all the details with maps or anything, as you would with serious usage. Instead, I just wanted a display to show me the boats, and a list of the details as well.

ais-targetlist

On one of my outing days, I decided to leave my laptop catching AIS, and recording the screen. Playing back the day’s recording at accelerated speed allows you to appreciate the AIS plot better, although in reality, it is slow to build and slow to update (especially in poor signal conditions).

AIS-FANIM

It was actually quite interesting and useful, because we could often see the ships moving and identify them before they came into our field of view at the hotel. This gave us a little heads-up as to what to expect “around the corner”.

Over time, I captured some screenshots of each of the boats that I saw, along with their unique MMSI number. This is like a “MAC address” for an AIS transmitter boat. Collecting them, along with their text identifiers, allowed me to build this table.

Name MMSI Carrying Belonging to
HANJIN DALLAS 218061000 Inmarsat B, C or M Germany
SANTA     BELINA 229980000 Inmarsat B, C or M Malta
EVER LOADING 235102681 Inmarsat A, Other UK
AZAMARA QUEST 256216000 Inmarsat B, C or M Malta
Unknown 304038000 Inmarsat B, C or M Antigua and Barbuda
MINERVA 309477000 Inmarsat B, C or M Bahamas
STAR PISCES 311000164 Inmarsat A, Other Bahamas
SUPERSTAR VIRGO 311000165 Inmarsat A, Other Bahamas
STARRY METROPOLIS 339300680 Inmarsat C Jamaica
HYUNDAI COURAGE 352698000 Inmarsat B, C or M Panama
IS CHINA 356247000 Inmarsat B, C or M Panama
SEROJA EMPAT 356575000 Inmarsat B, C or M Panama
HANJIN CHENNAI 357079000 Inmarsat B, C or M Panama
DONG TENG 372837000 Inmarsat B, C or M Panama
FI TAT 412000000 Inmarsat B, C or M China
MIN TAI 3 HAO 412441060 Inmarsat C China
Unknown 412460850 Inmarsat C China
HAIYANG 412460880 Inmarsat C China
SHUN DE 412460910 Inmarsat C China
ZHONG SHAN 412461640 Inmarsat C China
PENG LAI HU 412462060 Inmarsat C China
NAN SHA NO.68 412462570 Inmarsat C China
QI JIANG 412464160 Inmarsat C China
SHUNSHUI 412467870 Inmarsat C China
HAI MAN 412468690 Inmarsat C China
Unknown 412469320 Inmarsat C China
XIN YUN TONG 288 412470150 Inmarsat C China
Unknown 412470620 Inmarsat C China
YUE AN YUN 62 412470740 Inmarsat C China
Unknown 412473790 Inmarsat C China
JIN YUAN LUN 8 412475020 Inmarsat C China
YU SHENG658 412476170 Inmarsat C China
SHI TAI 628 412476240 Inmarsat C China
YI XIAN HU 412689000 Inmarsat B, C or M China
CUI HENG HU 412868000 Inmarsat B, C or M China
Unknown 412876000 Inmarsat B, C or M China
SHUNJING 412882000 Inmarsat B, C or M China
XING ZHONG 412884000 Inmarsat B, C or M China
JIANGONG178 413464350 Inmarsat C China
FANGZHOU3 413464760 Inmarsat C China
TONG CHENG 602 413465430 Inmarsat C China
FU XING DA 9 413465530 Inmarsat C China
HUI WAN 016 413471130 Inmarsat C China
PING YE 8 413472590 Inmarsat C China
NAN HANG 787 413474470 Inmarsat C China
DONG PENG [email protected]@@@@@@C\ 413690270 Inmarsat C China
EN CHENG 413695260 Inmarsat C China
JIAN_GONG_218 413762706 Inmarsat A, Other China
BAI FU 198 413900599 Inmarsat A, Other China
YUEGUANGZHOUHUO0883 413900892 Inmarsat A, Other China
ZHONG HANG 913 413900903 Inmarsat A, Other China
QIAOYANG6HAO 413902224 Inmarsat A, Other China
Unknown 413902778 Inmarsat A, Other China
Unknown 413904053 Inmarsat A, Other China
KMTC SHANGHAI 441902000 Inmarsat B, C or M Korea
KADIMOS 456730000 Inmarsat B, C or M Unknown
GUIA 477012000 Inmarsat B, C or M Hong Kong
PICO 477031000 Inmarsat B, C or M Hong Kong
SANTA MARIA @@@@@@BL 477032000 Inmarsat B, C or M Hong Kong
Unknown 477056200 Inmarsat C Hong Kong
UNIVERSAL MK2012 477056300 Inmarsat C Hong Kong
Unknown 477064000 Inmarsat B, C or M Hong Kong
SHENYANG 477195500 Inmarsat C Hong Kong
MARCO POLO 477197200 Inmarsat C Hong Kong
CASTELLA SQUARE 477197400 Inmarsat C Hong Kong
DI MODA SQUARE 477197500 Inmarsat C Hong Kong
UNIVERSAL MK3 477210000 Inmarsat B, C or M Hong Kong
SHANTOU 477249000 Inmarsat B, C or M Hong Kong
UNIVERSAL MK 2001 477303000 Inmarsat B, C or M Hong Kong
OOCL LONG BEACH 477316000 Inmarsat B, C or M Hong Kong
UNIVERSAL MK2016 477320600 Inmarsat C Hong Kong
UNIVERSAL MK2017 477320700 Inmarsat C Hong Kong
BARCA 477357000 Inmarsat B, C or M Hong Kong
SHANGHAI 477770800 Inmarsat C Hong Kong
WHAMPOA 477847300 Inmarsat C Hong Kong
THEGRANDCANALSHOPPES 477937100 Inmarsat C Hong Kong
THE VENETIAN 477937200 Inmarsat C Hong Kong
COTAI CENTRAL 477937400 Inmarsat C Hong Kong
THE PLAZA 477937700 Inmarsat C Hong Kong
COTAIARENA 477937800 Inmarsat C Hong Kong
COTAISTRIP COTAIGOLD 477937900 Inmarsat C Hong Kong
GOURMET DINING 477958100 Inmarsat C Hong Kong
FIRST FERRY V 477995027 Inmarsat A, Other Hong Kong
FIRST FERRY VII 477995029 Inmarsat A, Other Hong Kong
FIRST FERRY X 477995032 Inmarsat A, Other Hong Kong
FIRST FERRY [email protected]@@@B= 477995033 Inmarsat A, Other Hong Kong
DISCOVERY BAY 1 477995038 Inmarsat A, Other Hong Kong
DISCOVERY BAY 2 477995039 Inmarsat A, Other Hong Kong
DISCOVERY BAY 7 477995042 Inmarsat A, Other Hong Kong
PILOT20 477995051 Inmarsat A, Other Hong Kong
PILOT 1 477995053 Inmarsat A, Other Hong Kong
PILOT 3 477995055 Inmarsat A, Other Hong Kong
PILOT22 477995056 Inmarsat A, Other Hong Kong
PILOT23 477995057 Inmarsat A, Other Hong Kong
PILOT 9 477995061 Inmarsat A, Other Hong Kong
MAN [email protected]@@@@@@@@@@C7 477995062 Inmarsat A, Other Hong Kong
MAN [email protected]@@@@@@@@@@CL 477995063 Inmarsat A, Other Hong Kong
MAN KAI 477995064 Inmarsat A, Other Hong Kong
Unknown 477995073 Inmarsat A, Other Hong Kong
SEA SUPREME 477995074 Inmarsat A, Other Hong Kong
SEA SUPERIOR 477995075 Inmarsat A, Other Hong Kong
SEA SPRING 477995077 Inmarsat A, Other Hong Kong
SEA SMART 477995079 Inmarsat A, Other Hong Kong
PILOT 5 477995084 Inmarsat A, Other Hong Kong
PILOT15 477995091 Inmarsat A, Other Hong Kong
PILOT11 477995106 Inmarsat A, Other Hong Kong
PILOT18 477995109 Inmarsat A, Other Hong Kong
PILOT82 477995123 Inmarsat A, Other Hong Kong
PILOT83 477995124 Inmarsat A, Other Hong Kong
PILOT85 477995126 Inmarsat A, Other Hong Kong
PILOT88 477995128 Inmarsat A, Other Hong Kong
SHUN TAT 31 477995191 Inmarsat A, Other Hong Kong
SHUN TAT 22 477995204 Inmarsat A, Other Hong Kong
PILOT33 477995228 Inmarsat A, Other Hong Kong
WING HOP LEE NO 8 477995245 Inmarsat A, Other Hong Kong
SEA SPEED 477995251 Inmarsat A, Other Hong Kong
MD312 477995257 Inmarsat A, Other Hong Kong
SEA SPIRIT 477995260 Inmarsat C Hong Kong
GEOWORKS SB-1 477995332 Inmarsat A, Other Hong Kong
ANESUN 477995337 Inmarsat A, Other Hong Kong
DIVINGSUPPORT VESSEL 477995389 Inmarsat A, Other Hong Kong
PILOT36 477995390 Inmarsat C Hong Kong
PILOT35 477995392 Inmarsat A, Other Hong Kong
WING ON TRAVEL 477995405 Inmarsat A, Other Hong Kong
WAN HAI 313 565132000 Inmarsat B, C or M Singapore
KOTA SATRIA 565334000 Inmarsat B, C or M Singapore
TEMPANOS 636014648 Inmarsat A, Other Liberia
CSAV TYNDALL 636016321 Inmarsat A, Other Liberia
HS PARIS 636092461 Inmarsat A, Other Liberia
H.K.HARBOUR 900001236 Inmarsat A, Other Unknown
H.K.UNITED 7 B1244 900022890 Inmarsat C Unknown

I didn’t realize that the MMSI number follows conventions which reveals the country of registration and (used to accurately show) the satellite equipment on-board. At least, I can say that I’ve been able to receive and decode AIS signals.

It seems that none of the Star Ferry boats carry AIS, but the First Ferry boats do. There seems to be a lot of harbour pilot boats – many more than I expected, which really goes to show just how busy Hong Kong is. A lot of the traffic is heavy freighters.

Night Photos

One of the most interesting souvenirs was this torn fragment of police tape, left behind on a bridge pole. Apparently, earlier in the day, a person had attempted to commit suicide by jumping off the bridge near the hotel and the tape was used to cordon off the area.

Barrier Tape English Barrier Tape Chinese

Well, at night, we went back to the bridge to take a few shots of the lights, as it was already new year and they would soon be turned off. It wasn’t a particularly scenic area, spoilt by low-pressure sodium lamps.

20150102-2314-9239

The traffic in Hong Kong is immense though, and that proved to be a good opportunity for a long-exposure.

20150104-0052-9336

Feeling a little disappointed, we went to Central Plaza to get some other shots. Unfortunately, the baubles on the tree weren’t shiny enough …

20150103-0007-9283

Anyhow, we continued down to Great Eagle Centre, where some very interesting light made an appearance.

20150103-0016-9292

The roadway is bathed in a blue and purple tone, which gives the green trees an eerie, desaturated look. The low-pressure sodium lamp on the left gives the impression of a “sun”, and the sky is a dark, inky colour. One of my favourite shots.

The centre is home to a large bus terminal and interconnection bridge to the Star Ferry terminal.

20150103-0048-9322

Walking along the bridge allowed us to get closer to the ferry terminal and take a photo of another Christmas illumination.

20150103-0030-9300

So, why the strange coloured lights? Well, the whole area is lit by two massive lighted signs. A red Hitachi sign, and a blue and white China Mobile sign. These seem to be made of many many flourescent tubes, which can be seen in the full sized image..

20150103-0034-9306 20150103-0033-9302

This also gave me the opportunity to take this photo, which looks a bit “half and half”.

20150103-0045-9319

This outing helped break the monotony of spending a few days in the hotel room, not being able to walk.

Conclusion

I’ve come to the end of my radio adventures in the room. This brings us up to about 4th January, so there’s still quite a few more days of the holiday to go. More photos, and less technology, to come in the next few parts!

About lui_gough

I’m a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!

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8 Responses to Trip to HK & CN 2014 – Part 5: RTL-SDR, More Radio, AIS & Night Photos

  1. SydneyCityTV says:

    I’m sure you’ve noticed this before but I believe that quite a few (but not all) stations here in Sydney also have slideshow images on DAB+ Digital Radio. Of course, how this feature is used varies by network. Some stations only have logos or promotional images, while others have song info, news & weather information, etc.

  2. John says:

    Hi, great blog post! I’m embarassed to say you have explored the spectrum here many times better than I have and I live in Hong Kong!
    I am currently feeding liveatc.net with audio and sites like flightaware/flightradar24 with adsb and aprs.fi as well. ADSB site: bobsaget.mooo.com:8080

    Also about to start feeding marinetraffic.com with AIS data as soon as their hardware arrives.

    If you make it back here, please let me know.

    • lui_gough says:

      Nice to hear from you John! Don’t worry, you have all the time to go and explore :). It’s always interesting to look at the airwaves “away from home” – admittedly, I haven’t done such a good job with Sydney either, mainly because it’s “everyday” for me, just like Hong Kong would be “everyday” for you. The time-limited factor gives a good incentive to explore as much as possible, because I don’t know when I would be back next.

      Good to hear that you are contributing – I used to use GlobalTuner’s Hong Kong site to do a few quick tunes here and there, but time is always very limited. Being involved in full time study, travel opportunities are limited, but I’ll be sure to let you know if I do return :).

      – Gough

  3. Pingback: Project: Scanning Sydney’s DAB+ & FM Broadcasts | Gough's Tech Zone

  4. Pingback: Analyzing the Radio Spectrum in Hong Kong with an RTL-SDR - rtl-sdr.com

  5. 李耀宗 says:

    There are (actually, were) two types of First Ferry Boats, one for local service and the other is international service (specifically, going to Macau.) The local boats doesn’t carry AIS (as Star Ferry), only international boats did.

    FYI, the Macau ferry business was sold to TurboJET now.

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