Friday, May 27, 2011

Model 4686 Silvertone 1937 Console radio restoration

Re-wired the line voltage and power switch circuitry, adding a grounded power cord, fuse, new safety caps, and cable clamp.

Re-caped all electrolytics.

Re-caped about 1/3 of the paper capacitors.

Oiled the tuning mechanism, which is a unique 'dial a tune' thing that functions much like a rotary telephone, where you dial in the station you want to hear.

More later...

Thursday, May 26, 2011

NTIA Seminar Series on Spectrum Measurement Theory and Techniques

Check out this video series online on how to measure radio transmitters, mostly for radar. Not an easy thing to do for sure.

ITS Educational and Training Videos

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SP-09-460: NTIA Seminar Series on Spectrum Measurement Theory and Techniques

Have you ever wondered how a spectrum analyzer works, how to properly adjust all of the analyzer's parameters, or why a stair-step pattern initially appears on a spectrum analyzer screen when you turn it on? Do you know how to precisely calculate the analyzer's sensitivity in your head, merely by glancing at the screen display without any signal present? Are you uncertain about how much gain, and how low a noise figure, you ought to specify when you are ordering a low–noise amplifier (LNA) for a radio receiver? Do you want to know the difference between noise figure and noise factor? Do you wonder how to diagnose and solve radio interference problems?

If you have questions about how to make good radio spectrum measurements or how to diagnose interference problems, you will find the answers in the NTIA Seminar Series on Spectrum Measurement Theory and Techniques. In this series of talks, an NTIA engineer at the Institute for Telecommunication Sciences (ITS) laboratory in Boulder, CO, discusses the fundamentals of radio spectrum measurements. The speaker, Frank Sanders, who has nearly thirty years of experience in this field, recognizes that even for many engineers who routinely use spectrum analyzers, the fundamentals of how they work and how to use them may be a bit murky; even in university lab classes the instructors do not always understand these machines very well themselves.

Most of the talks, which are 80–100 minutes long, are divided into two parts. In the first portion of each video, Sanders explores a particular aspect of radio spectrum measurement technique or theory with a whiteboard lecture. In the second part, the lessons of the whiteboard discussion are implemented with actual measurement hardware and radio signals. A few of the talks, which for example involve large numbers of photographs of radar systems, are videos of his Microsoft Powerpoint presentations.

In this series, Sanders explains spectrum analyzer functionality in terms of convolution bandwidth and shows how, when convolution is understood along with the mechanics of analyzer design, spectrum analyzer operations and outputs become easy to understand and use. Other topics include (1) what you need to know to use spectrum analyzers to examine all types of radio signals, including mobile radios, radars, and digital data links; (2) the use of low noise amplifiers and how to specify the right gain and noise figure for your receiver and measurement applications; (3) how radar systems work, and how to understand and interpret the signals that you see coming from radars; (4) the ways that radio interference can occur; (5) a methodical approach for diagnosing and solving radio interference problems; (6) the math needed to convert spectrum analyzer measurements into field strengths of radio signals; and (7) the proper conversions for radiation hazard calculations.

Monday, May 23, 2011

5/24 @ 4pm: The MIT IAP 2011 Radar Course: Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar (SAR) Imaging

For those of you who are interested in the build a radar course I am presenting a talk on this at the IEEE Life Affinity Members, AP-S, AES, and GRSS joint meeting at 4pm on May 24 at Lincoln Laboratory.

All are welcome but you must pre-register by following the directions at the bottom of the talk summary here:

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Summary of talk:

Recently MIT Lincoln Laboratory sponsored a short radar course at MIT main campus during the January 2011 Independent Activities Period (IAP). The objective of this course was to generate student interest in applied electromagnetics, antennas, RF, analog, signal processing, and other engineering topics by building a capable short-range radar sensor and using it in a series of field tests. The underlying philosophy being that students have a vested interest in making their own radar work properly, causing them to dig deeper into these subjects on their own volition thereby providing a self-motivated learning experience. A series of lectures on the basics of radar, modular RF design, antennas, pulse compression and SAR imaging were presented. Teams of three students received a radar kit. Nine teams participated in the course.

The radar kit was an S-band coherent frequency modulated continuous wave (FMCW) radar centered at 2.4 GHz with less than 20 mW of transmit power developed by the authors. To reduce cost, the antennas (transmit and receive) were made from coffee cans in an open-ended circular waveguide configuration. To clearly show the RF and analog signal chain, all components were mounted on a block of wood similar to an early 1920’s radio set. The microwave signal chain was made from six Mini-Circuits coaxial components. The analog signal chain was implemented on a solderless breadboard for quick fabrication and easy modification. The video output and transmit synchronization pulses were fed into the right and left audio inputs of any laptop computer. To make the kit portable it runs on eight AA batteries. The total cost of each kit was $360.

The radar operates in three modes; doppler vs. time, range vs. time, and Synthetic Aperture Radar (SAR) imaging. To record data a student uses the .wav recorder program in the laptop. MATLAB scripts read the .wav data and form the appropriate plots.

Of the nine student groups all succeeded in building their radar, acquiring doppler vs. time and range vs. time plots. Seven of the nine groups succeeded in acquiring at least one SAR image. Some groups improved their radar sets by improving the signal processing algorithms, developing real-time radar graphics user interfaces (GUI’s), and by making a more robust chassis.

Most students were from MIT but a small contingent were from Northeastern University and one student built this radar as an independent study at Michigan State University. Great enthusiasm was generated after each field test. Students were engaged throughout the course and they continue to ask questions about how to improve the performance of their radar sets and how to make more sophisticated systems. Many students discussed scattering theory at length when trying to interpret their SAR imagery.

In summary, it is difficult to introduce the current generation of students to the field of applied electromagnetics, RF, analog, and signal processing because of the numerous challenging prerequisites needed before the rewards can be realized. By presenting these difficult topics at a high level while at the same time making a radar kit and performing field experiments, students became self motivated to explore these topics. In the long term, courses using this continuous engagement philosophy could help fill the gap as the current generation of radar engineers continues to retire.

More info about this course can be found:

MIT Lincoln Laboratory: MIT Lincoln Laboratory researchers introduce students to radar engineering

A Modern Approach to Radar | CSAIL

Links to student results and blog entries here.

Wednesday, May 18, 2011

Model 4686 Silvertone 1937 Console radio restoration

Starting the restoration of my Silvertone model 4686 console radio. This radio was built in 1937. It works on the standard broadcast AM band and 3 short wave bands.

This radio features a magic eye tuning indicator and a really big speaker with a massive baffle.

The chassis is in excellent condition.

To my surprise, the seller actual plugged it in and it works. Although, it needs alot of work. I found some of the repairs inside to be sub-standard and quite dangerous.

More later as restoration proceeds.

Friday, May 13, 2011

Free Video Courses in Radar Systems Engineering, by Dr. Robert M. O'Donnell

Sponsored by IEEE Aerospace and Electronic Systems Society and the IEEE New Hampshire Section, for all lectures please goto:

From the intro slide:

This Free Radar Systems Engineering Course (video, audio and screen captured ppt slides) and separate pdf slides) has been developed as a first course in Radar Systems for first year graduate students, advanced senior undergraduates, or professionals new to radar (In the first 17 lectures there are over 1150 slides!)

The video course will contain the screen captured audio and video along with the screen capture of each viewgraph. The textbook for the course will be "Introduction to Radar Systems" 3rd Edition McGraw Hill 2001. Homework problems are taken mostly from that textbook. s Although Skolnik's text is the "text book" over fifty textbooks, (including the recently published text, "Principles of Modern Radar" by M. Richards et al ) and scores of journal articles were read to develop the material in this course. In addition, each lecture has a significant number of references at its end. Each lecture will vary in length from 30 minutes to up to 2 hours. Most will be somewhat over an hour. The video stream of each topic will be broken up into "easily digestible" pieces of approximately 20 to 30 minutes."

Wednesday, May 11, 2011

phased array radar imaging a 12 oz soda can moving in free-space in near...

Nearly a real-time image of a moving soda can from a near-field phased array radar that i built in my garage as part of my dissertation.

Other videos show this radar imaging the same moving soda can through a 4" concrete slab.

Sunday, May 8, 2011

my ARRL Homebrew Challenge 3 entry, RX/TX audio, keying circuits, and microphone installed

Update on the HB3 radio for 10m/6m SSB/CW, in the breadboard stage.

Added a plate for all of the front panel controls.

RX audio signal chain works. TX audio signal chain works. Microphone installed. Microphone keying circuit works, radio will transmit -10 dBm PEP.

Next step:
Moving on to the side tone oscillator and CW keying circuit.

After that:
Will make the pre-driver board to get up to 1 watt or so TX.

Stay tuned for the latest updates.....

Wednesday, May 4, 2011

my entry in to the ARRL Homebrew challenge 3, 10m/6m SSB and CW transceiver

Shown here is my entry into the ARRL Homebrew Challenge 3. This is a 10m and 6m SSB transceiver, currently in the breadboard prototype stage.

Receiver works well so far and I have already tuned in some DX on 10m.

Next step will be to consider filtering the first LO further and to order the proper BFO crystal for USB.

Once these steps are complete i will move on to the audio and keying board, which will first be implemented using a solderless prototyping board.

Sunday, May 1, 2011

phased array radar imaging a cylinder moving in free-space in near real-...

Posted more results from my dissertation to youtube.

Here we are imaging a cylinder moving in free-space (outdoors) in near-real time.