Tokyo Open Source Conference 2015 (Autumn)

A few weeks ago I went to Tokyo's Open Source Conference and tried to learn as much as I could. As always, it took place at Meisai (明星大学) University. You can find here some of the presentation slides and videos. Explaining everything would be too much of a burden so I will just write down a list of things I learned about:

ESP8266, Cloudstack (docker demo), GUST, fluentd, kinesis, storm, Diameter, OpenStack, Snappy, hacking Linux devices, Hatohol, GrowthForecast, mongodb, zabbix, hinemos, Symfony2, Snap, Optaplanner, Spark, Kuromoji, mecab, Kafka, hadoop, yarn,, moebuntu, Timeglider, Ubuntu JUJU, LTSP, TWRP, kibana, elasticsearch, PostGIS, OpenLayers.js, MapServer, TinyOWS, QGIS, Wikipedia word analyzer, aozorahack, plamo.

I also gave a short presentation during the lightning talks time about how to access your home's computer through a browser using the software shellinabox.

Hiking near Tokyo: Mt. Jinba

Since I moved to the Kantou region (Tokyo and surrounding prefectures), I have only hiked Mt. Nokogiri and Mt. Takao. This post reports on my third hike around Kantou: Mt. Jinba (陣馬山).

First, take a train to Fujino station (藤野駅). From Fujino station, get on the bus no.8, and get off at the last stop (和田, Wada). You are 355m high now. The bus ride is 247yen (as of Sept/2015) and takes 14min. You can pay either with an IC card (e.g. suica or pasmo) or in cash. You can check the timetable on google maps by specifying 神奈川県陣馬自然公園センター (Kanagawaken Jinba Shizen Kouen sentaa) as your destination. My bus departed at 9:50 and the next one was leaving at 13:10. Make sure that you check the departure times in advance.

Walk on the same direction as the bus. After 3-4 minutes you will find the entrance to Mt. Jinba on your right. Then, walk up until the top of Mt. Jinba (855m) which will take you about an hour and a half. At the top of the mountain there is this phallic sculpture of a horse. Notice that the name of the mountain is composed of two Kanjis: 陣 (Camp) and 馬 (horse). If you are lucky, Mt. Fuji will be visible from the top. But don't count on it during Summer or Autumn. From the top, I could also listen to quite a few amateur radio stations.

Walk down the mountain using a different trail (栃谷尾根, Tochiya One). There are several trails and it's a bit confusing. Make sure you follow the one indicated by the sign in the picture above.

Whereas the walk-up is mostly inside the forest where you can't see much, the walk-down has much better views. After approximately 50 minutes of walking, you will see a sign with the letters 陣馬の湯 (Jinba-no-yu) or 陣渓園 (jinkeien) written on it. You can have a hot bath and some tea there for 1000 yen (Sept/2015).

After a refreshing stop, continue walking down. For some reason, I found many dead snakes on the road. Fortunately, I also saw many insects alive. After 30 minutes, get on bus no. 8 back to Fujino station (陣馬登山口バス停) or just walk your way to Fujino station. It's not that far.

Conclusions: this is a nice super-easy hike perfect for a 1-day trip from Tokyo and surroundings. With only 580m of ascend and 740m of descend, you can complete this course in less than 3 hours. Most importantly, it's not crowded like Mt. Takao.

First experiences with Software Defined Radio (SDR)

Software defined radio (SDR) consists of implementing most of the components in a radio transmitter or receiver (filters, modulators, mixers and the like) using software. The only parts that remain analogue (the RF front end) are a high frequency low-noise amplifier connected to the antenna, switchable band-pass filters, and a variable-frequency oscillator that moves the received signal down in frequency for it to be sampled with a high-speed analogue-to-digital (A/D) converter. I would say that the advance of A/D converters, with increasing conversion speeds, is the key enabler for this technology.

For beginners, I suggest to buy a DVB-T dongle based on the Realtek RTL2832U chip. These dongles, originally made for watching TV on your computer, are very cheap (I got mine for 1000 yen) and well-supported by the rtl-sdr project. If you have the money you can try other boards specifically made for SDR such as osmoSDR, FUNcube, USRP, bladeRF, HackRF or VNWA3 (as my friend Paco suggests) for example. As I explain in my SDR notes, you can test your DVB-T dongle on Linux using the following command (82.5MHz is the NHK radio frequency in Tokyo):

$ rtl_fm -f 82.5e6 -M wbfm -s 200000 -r 48000 - | aplay -r 48k -f S16_LE

Other radio frequencies I could listen from my home were:
  • NHK: 82.5MHz (Tokyo)
  • Tokyo FM: 80.0MHz (Tokyo)
  • FM yokohama: 84.7MHz (Yokohama)
  • Inter FM: 76.1MHz/89.7MHz (Tokyo) / 76.5MHz (Yokohama)
  • 放送大学: 77.1MHz (Tokyo)
  • J-WAVE: 81.3MHz (Tokyo)
  • Bay FM: 78.0 (Chiba)
  • Nack 5: 79.5 (Saitama)
  • Radio city: 84.0 MHz (Tokyo)
  • FM844: 84.4MHz (Tokyo)

Apart from being able to listen to a wide range of frequency bands, the fun part of SDR is that since the signal is all handled by software you can do whatever you want with it. For example, one of the most expensive equipment for an amateur radio fan is a spectrum analyzer. Thanks to SDR and an awesome software called 'gqrx' (powered by the amazing GNUradio project) you can turn your cheap DVB-T dongle into a spectrum analyzer.

Watching the spectrum was useful for understanding why my FM microphone wasn't behaving as expected. In fact, I found out that the center frequency of my FM transmitter was moving around quite a bit and that was the reason it was rather hard to tune.

An not only that, you can also easily create your own receiver designs by using a software called 'gnuradio-companion' that already has a lot of blocks ready for you to use. I shared my gnuradio-companion designs on my github account.

Conclusions: SDR is really fun and will give you insights on how signals are sent, received and processed. I wish I had had the chance to use SDR when I studied electrical engineering (telecommunications) at University. Make sure you check my notes and gnuradio-companion designs on github.

Ham Fair 2015 (Tokyo)

Last August I attended Tokyo's ham fair 2015.

Actually it was my second time attending this event, and I was very excited because this time I had my own amateur operator license (see my previous post here). The picture shows my call sign (JI1OJQ) painted with ketchup onto an omurice at a maid bar in Akihabara.

This year was also special because a friend of mine had his own booth. My friend sells retro stuff (vacuum valves and the like) at Ikenoya radio in Akihabara's electronic town. Apart from that, I found an interesting radio amateur group of people called yama-to-musen (mountains and radio). Climbing two separate mountains and trying to communicate from the top sounds like fun.