Wednesday, March 28, 2012

Join us for Science on Saturday at MIT Lincoln Laboratory: Radar


If you have kids consider joining us for a Science on Saturday interactive demo & presentation on Radar, Saturday March 31, 2012.  For more details and to sign up:


We will show doppler radar, ranging, radio propagation, traveling waves, and numerous other fascinating live physics experiments.

Hope to see you there!

Sunday, March 25, 2012

Repairs to Frankenstein, a vacuum tube home theater system



The quad amplifier on my tube home theater system failed about a month ago.  It was burning through fuses.  I suspected a shorted output pentode because half of the pentodes are over 10 years old and had many hours on them.

I removed all of the tubes, but when i threw the power supply switch the fuse continued to blow.  I suspected a bad capacitor but the amplifier is not old enough yet.  I was surprised to find a bad rectifier diode.  After replacing this and replacing all of the old pentodes for good measure i re-biased the amplifier to 25 mA for each of the 8 tubes for class B operation.

I will see how things go with the new pentodes at this bias current then increase later if i think it is necessary.

I'm happy to report that everything sounds great and is working reliably.



Thursday, March 22, 2012

Low-cost new microwave test equipment

QM-AR2010-4400

138 MHz - 4.4 GHz, .5 dBm output steps, up to 10 dBm output power.  A microwave signal generator on a USB stick for $500:
http://www.quonsetmicrowave.com/QM-AR2010-4400-p/qm-ar2010-4400.html

More equipment along these lines can be found here:
http://www.quonsetmicrowave.com/category-s/52.htm

This is a very interesting development in low-cost microwave test equipment.  The price point for this gear is so low that accessibility to test gear will be greatly increased and time saved from hunting for test gear at hamfests, which usually takes years to find the right piece.

Tuesday, March 13, 2012

ARRL Homebrew Challenge 3, the results are in

I'm very excited to report that my HBC3 challenge radio will be in QST!  It was an very difficult challenge to be sure and an amazing life experience.

For a complete build video:
('http://www.youtube.com/p/0B78D8A3B74F467E?version=3&hl=en_US',)



And on the ARRL.org website, this article:
http://www.arrl.org/news/view/the-arrl-homebrew-challenge-iii-and-the-winner-is

For complete documentation and more info:
http://www.glcharvat.com/Dr._Gregory_L._Charvat_Projects/6_%26_10m_SSB_CW_Transceiver.html

Saturday, March 10, 2012

6.002x Mongolia




A friend of mine, Tony Kim, will bring MIT's 6.002 curriculum to Mongolia!  He will do this by starting a https://6002x.mitx.mit.edu/ program in country.

So far he has made large orders of electronic components, test gear, and will even bring the coffee can radar along.

Be sure to follow the exciting progress here:
http://6002x.blogspot.com/
(I will add a link to my blog list on the right side)

Saturday, March 3, 2012

Learn about radar by doing it, sign up now for MIT Prof. Ed. radar courses









Learn about Synthetic Aperture radar by making your own:
MIT Professional Education is offering a course in the design, fabrication, and test of a laptop-based radar sensor capable of measuring Doppler and range and forming synthetic aperture radar (SAR) imagery. Lectures will be presented on the topics of applied electromagnetics, antennas, RF design, analog circuits, and digital signal processing while at the same time you build your own radar system and perform field experiments. Each student will receive a radar kit, designed by MIT Lincoln Laboratory staff, and a course pack.
http://web.mit.edu/professional/short-programs/courses/radar_systems.html

Learn about phased array radar systems by making your own:
MIT Professional Education is offering a unique course in the design, fabrication, and test of a laptop-based digital phased array radar sensor capable of ground moving target imaging (GMTI). Lectures will be presented on the topics of applied electromagnetics, antennas, RF design, analog circuits, radar system modeling, and digital signal processing while at the same time you build your own phased array radar system and perform field experiments. Each student will receive a radar kit, designed by MIT Lincoln Laboratory staff, and a course pack.
http://web.mit.edu/professional/short-programs/courses/phased_array_radar_sensor.html