Few words about me:

From very childhood I loved computers, electronics, lasers, sulfuric acid and liquid nitrogen. I always wanted to be making microchips, UAVs and see nuclear explosion.

Now I am doing software engineering and in the spare time - some microelectronics and physics/chemistry experiments.

I live and work in Russia, Moscow.

Temperature stability of AirSpy SDR receiver

Recently I got AirSpy SDR-receiver : it has 20Mhz/12bit ADC comparing to 2.4Mhz/8-bit one in RTL2832-based devices. Capture bandwidth is 9Mhz. Also, it uses TCXO with 1.5ppm frequency error spec. In this article I focus on it's frequency error vs temperature. More detailed review of AirSpy will follow in the nearest days...

BTW, for the first time in human history we have blueberry-cooled electronics:

Here are frequency errors. I was measuring 35-th harmonic of FE-5680A rubidium frequency standard generating 2^23 Hz, i.e. ideal frequency should have been 8192*1024*35=293'601'280 Hz.

HardwareQuartz (E4000+RTL2832)AirSpy TCXO
After warm-up293'627'555 Hz +89.49ppm293'601'318 Hz +0.129ppm
Tcase ~0C293'626'824 Hz +87.00ppm293'601'185 Hz -0.324ppm
Tcase ~60С293'628'227 Hz +91.78ppm293'601'386 Hz +0.361ppm
January 4, 2015

I didn't make it to amateur astronomy (this time)

Recently I've bought telescope optical tube assembly - Levenhuk 200mm F4 carbon - there was nothing else in this class left in stock in Moscow, all sold out. But, as one could expect, chances to get decent Chinese F4 parabolic mirror are slim...

December 23, 2014

Brief test of DPSS laser parts

Finally got some time to play with neodymium solid state lasers : ordered 2W IR 808nm laser for pumping and few glued crystal assemblies of YVO4:Nd+KTP (size 0.8*1.3*2.5мм). Unfortunately supplier made a mistake and sent 400mW IR laser instead of 2W one and promised to send the replacement. Meanwhile I decided to run few tests on the table with this first laser.

After focusing IR beam on the crystal generation immediately started as well as second harmonic generation - nice green spot appeared on the targer:
November 23, 2014

Globular cluster M15

62 minutes exposure on T24 telescope from iTelescope.net (61cm aperture).
50 minutes for luminosity, and 4 minutes each for RGB with 2x2 binning. Apparently, color shots needed more time to lower noise.

The brightest starts in the cluster have magnitude of 12.6, and that super-bright star at the top-right part of the photo has magnitude 7.6 (which is twice weaker than we can see with our eye in perfect conditions). There are more than 100'000 stars in this cluster.

November 15, 2014

ZnSe lenses for CO2 laser: plano-convex vs convexo-concave

Some time ago I've bought CO2 laser engraver from China. It had lots of issues, including bad lens, which supplier had to replace. I've chosen 102mm replacement lens that time. A month ago I noticed that price of 20mm ZnSe lenses on ebay dropped to 15$, so I ordered more suitable lens for my engraver with 51mm focal length. When it arrived I was pleased with quality of edges and coating, but was surprised to see that it is an convexo-concave lens instead of usual plano-convex type.

On the left - first bad lens, on the right - replacement sent by supplier and in the middle - this new one.

Is there any practical difference between plano-convex and convexo-concave lenses for CO2 laser focusing? Also, which way one should mount it? Let's try to figure it out...
November 15, 2014

445nm laser diode Nichia NDB7875

So much time without new lasers... I had to stop this! Just received Nichia NDB7875 - 445nm laser diode with nominal power of 1.6W:

Through the window one can see laser itself and static discharge protection device (it looks like small cube):
October 28, 2014

Giant sunspot group on the Sun

I've though that last time I've seen big sunspot... But today there was just enormous sunspot group, largest since 1990, it's about 128'000 km wide.

October 24, 2014

Another step to the future - 4G/LTE in Moscow

All major mobile operators in Moscow already got their LTE frequencies in 800 and 2600Mhz bands, and already operating. Year ago I used Yota (they had the first operational LTE-Advanced network in the world) for temporary internet access, and now Beeline decided to put some real stress on the network and offered unmetered and free traffic on LTE till 15th of Jaunary. Ofcourse it was very hard to resist this, given that my phone already supported LTE. The only thing I needed to do was to update SIM card to a 4G-ready one.

Speeds appeared to be a big step forward compared to 3G and (especially) 2G. Apparently, there are still not many LTE-capable clients.

Worst case speeds are 20 mbit/sec (center of the city, in the building).

2 hour after enabling LTE - cable internet provider "2COM" decided to make "feeling of the future" even more palpable - they were cold-calling and promoting their new infrastructure where each client is getting 1 Gbit/s Ethernet cable, with maximum available Internet speeds of 500 Mbit/s (symmetrical, unmetered)... Unfortunately they had my old address, and in my current building they still had no equipment, so I will have to continue suffering with mere 100 Mbit/s Internet... I guess outstanding Internet access is probably one of the best perks of living in Moscow.
October 15, 2014

Finally some nice spots on the Sun to observe

Largest spot is greater than Earth...
September 12, 2014

UNIS tbm de Luxe typewriter

During my childhood in the village I was learning to type on a typewriter. It was some electrical typewriter, "Yatran" if I recall it correctly.
Recently I accidentally got mechanical Yugoslavian UNIS "tbm de Luxe" typewriter in a leather case - it seems they were very popular in USSR back in 1960-80's.

It is quite hard to type on it as it requires to hit keys with much higher force.
So blind 10-finger typing is impossible without lots of extra physical exercises :-)

Also scored 3 last typewriter ribbons from local e-shop. These were made in Belarus in 2013. It's surprising that typewriter ribbon is still in production (BTW manufacturer guarantee that it is good for only 2 years since manufacturing). Probably typewriters are still in use in some government agencies (due to secrecy?)

On this photo it is still with old ink tape:
August 24, 2014