Thursday, December 30, 2010

Care to process some airborne SAR imagery? GOTCHA VOLUMETRIC SAR DATA SET, available upon request

I found this awesome youtube video of a airborne SAR data set from all aspect angles. Apparently you can download this, the


on request from this page.

Sounds like a great opportunity to process some airborne SAR data.

Tuesday, December 21, 2010

Charvat Florist Making a Christmas Floral Arrangement.m4v

If you like this blog then support my dad's flower shop. This shop has been in the family since 1893 and has supported many of my engineering endeavors and college tuition payments.

In this video my dad shows step-by-stop how to make a floral arrangement for your holiday party. You can get the greens by taking a walk in a local park, but consider getting the flowers from my dad's flower shop, he will deliver anywhere:

Repairing the HP141T based spectrum analyzer

The 8552 IF section of my 10Mc-18Gc spectrum analyzer (HP141T with the 8555A plug-in and 8552 IF) stopped working recently during the fabrication of the MIT IAP course radar. While trouble shooting the problem i took these photos to show the insides.

The 141T/8552/8555A remains my favorite spectrum analyzer. Now that it is working again i hope to get a few more decades of use out of it.

Saturday, December 18, 2010

MIT students sign up now for the winter 2011 IAP course: Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar..

Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar Imaging
Dr. Gregory L. Charvat, Mr. Jonathan H. Williams & Dr. Alan J. Fenn, Dr. Stephen M. Kogon, Dr. Jeffrey S. Herd
Mon Jan 10, Fri Jan 14, 21, Mon Jan 24, Fri Jan 28, 10am-12:00pm, 56-114

Enrollment limited: advance sign up required (see contact below)
Signup by: 07-Jan-2011
Limited to 24 participants.
Participants requested to attend all sessions (non-series)
Prereq: Participants supply their own laptop with MATLAB installed

Are you interested in building and testing your own imaging radar system? MIT Lincoln Laboratory is offering a course in the design, fabrication, and testing of a laptop-based radar sensor capable of measuring Doppler, range, and forming synthetic aperture radar (SAR) images. You do not have to be a radar engineer but it helps if you are interested in any of the following; electronics, amateur radio, physics, or electromagnetics. It is recommended that you have some familiarity with MATLAB. Teams of three will receive a radar kit and will attend a total of 5 sessions spanning topics from the fundamentals of radar to SAR imaging. Experiments will be performed each week as the radar kit is implemented. You will bring your radar kit into the field and perform additional experiments such as measuring the speed of passing cars or plotting the range of moving targets. A final SAR imaging contest will test your ability to form a SAR image of a target scene of your choice from around campus, the most detailed and most creative image wins.
Contact: Dr. Gregory L. Charvat, (781) 981-3122,

Thursday, December 16, 2010

Cable Lacing, the way radios ought to be made

Peter AI4PP/SV0XAW noticed my old-school looking homebrew 20m SSB transceiver on the solder smoke blog. After looking at the photos inside of the radio he suggested i should try cable lacing for my next project.

Cable lacing is a method of dressing a wiring harness before wire ties inside of a piece of equipment. If you open up an old military radio or piece of HP test gear from the 1950's you will see cable lacing. Creating radio equipment is an art form and cable lacing provides a nice finishing touch.

Thank you for the suggestion Peter, I plan to look into this for my next radio project.

(images from

Monday, December 13, 2010

National Semiconductor Web Bench

I'm a big fan of National Semiconductor's Web Bench. Recently i have used it to design a 4th order active low-pass filter that worked well first time i tried it.

Similar results would occur if you were to scale designs from my favorite active filter book, Lancaster's Active Filter Cookbook.

Two resources to keep in mind next time you are required to use an active filter.

Thursday, December 9, 2010

My new grid dip meter, the Heathkit GD-1B

I purchased a new (old) grid dip meter a local hamfest for $10, the Heathkit GD-1B. Built in the 1950's this grid dip meter still works great, no need to restore it and it came with a full set of coils.

I plan to use this for, among other things, finding the AL values of salvaged toroid cores.

Sunday, December 5, 2010

Tubes or Transistors?

I have received many questions asking why I prefer the sound of tubes more than all of the solid state amplifiers i have heard to date. Fortunately, IEEE Spectrum has addressed this tube sound phenomenon and the industry of tube amplifier manufacturing in, 'The Cool Sound of Tubes.' One of the most interesting parts of this article is the comparison of several different solid state AF gain stages to triode and pentode equivalents. It was found that the triode produced the least harmonic distortion and provided greatest dynamic range of all. It is important to note that these test circuits did not use degenerative feedback which would certainly lower the harmonic distortion in all circuits, it would be interesting to perform this test.

Non the less, i think this is a fine article discussing the tube vs. transistor issue and it provides an overview of those who prefer to use tubes and have a the best reasons to do so.