Skip to main content


Showing posts from March, 2011

Easy HR607 Letter Creation

The ARRL is encouraging all amateur radio operators to write the congressional representatives about a bill before congress that would reduce frequency privleges on the 70 cm band, HR 607. KD4PYR has created an FB web application that creates a letter for you based on the ARRL's sample letter. Just input your call sign and a letter will be created with your name and address. The application even uses your call sign address to automatically fill in information about your specific representative!

HR607 in the news

HR607, the bill proposed by Representative Peter King, received some interesting coverage regarding it's effect on amateur radio in USA Today yesterday. It seems the letter writing campaign suggested by the ARRL may be working. The following excerpt is taken from the USA Today article:
"America's first responders, including law enforcement officers and firefighters, these front-line heroes still do not have a national interoperable public safety wireless broadband network," King said.
He added that efforts are underway to address concerns of ham radio operators and others.
Rep. Billy Long, R-Mo., a co-sponsor of the bill, said he will work "to ensure that we are not cutting any vital emergency services and not adversely affecting ham radio operations."

Find out how you can help.

Amateur Radio and HR 607

The ARRL and AMSAT have recently pointed out that a bill before the House of Representatives would adversely affect frequencies used by amateur radio. The video below describes the ARRL's stance and what you can do. Scroll down for links to a template letter for your representative and the address to send it to.

A sample letter can be downloaded from:
ARRL Sample Letter

For those without Microsoft Word, the letter is copied below.

You can send your letter to the ARRL's Washington Representative:

John Chwat
Chwat & Co.
625 Slaters Lane
Suite 103
Alexandria, VA 22314

who will expedite its delivery to your representative.

=========================Copy of sample letter===============================

The Honorable ____________________
United States House of Representatives
______________ House Office Building
Washington, DC 20515

Dear Representative ________:

As a voter in your district and as one of the nearly 700,000 federally licensed Amateur Radio operators across the nation, I ask tha…

Beach Hinges: What are They?

Anyone know what these are for? Found on a beach in NY.

Notes on Emmy Noether and Group Theory

Just a few quick notes on historical trails I'm finding as I study group theory and Emmy Noether's theorem. The people involved are a bit of a group themselves. The first person I found is Lagrange. He introduced the Langrangian, one of the key concepts of analytical mechanics. It's used today, well, everywhere, from plain old mechanics to quantum mechanics, to quantum field theory. He also laid some of the foundations of group theory working on permutation groups and their use in solving polynomials.

That brings us to Évariste Galois. Galois read Lagrange's papers at the age of 15. He later went on to develop Galois theory. Galois theory relates permutation groups of the roots of polynomials to their solvability.

Sophus Lie developed Lie groups, provide a framework that is similar to Galois theory for studying the symmetries of differential equations.

And that brings us to Emmy Noether. Her paper on "Invariant Variation Problems" applied Lie's wo…

Emmy Noether and Women's History Month

Coincidentally, during Women's History Month, I'm studying Emmy Noether's work on symmetric groups and conservation laws in physics. There's a great Wikipedia entry on her life and work. I found links to her conservation paper in both English and German at UCLA's Women in Physics site. There are a few books about her life and her theorem that look interesting. I'll be reading "Emmy Noether's Wonderful Theorem" later this month.

She spent her last few years at Bryn Mawr College a few miles from Philadelphia. Her ashes are scattered below the cloisters there. If you'd like to travel to the college, a map and transit information is included below. It turns out that it's pretty simple via SEPTA once you get to Philadelphia.

View Emmy Neother in a larger map

New Mexico Sunset

6th and 7th Grade Math Champs Build Ham Radios... You Can Help!

The following announcement about an awesome program for 6th and 7th graders came through on the RockMite mailing list this morning. Read on to find out how you can help out!

Thirty two "Math Champs" honor students from the 6th and 7th grades at Blaine Middle School in the state of Washington will be building and operating Small Wonder Labs Rock-Mites. The Math Champs represent their school in the Washington State Math Championships. They have finished the first week of their amateur radio program, which is a regular part of their schoolwork – not just an optional after-school activity.

The 32 students each belong to a work group of four students representing a DX country, and they have corresponding mock callsigns which are not currently assigned to any real hams:

Joseph: 3A2JSA, Gavin: 3A2GM, Monika: 3A2MK, Lauren: 3A2LKO, Candace: 9N7CO, Delaney 9N7DN, Kaylee 9N7KM, Darien 9N7DJ, Logan: ET3LN, Chase: ET3CL, Sawyere: ET3SH, Allan: ET3AL, Sarah: HH6SD, Holly: HH6HJ, Andy: HH…

Groups Made Easy: Group Definition

Just recording my notes on learning group theory into a series of short highlight videos.

Around the Lab: Diamagnetic Levitation and the levitating pan

What you're watching below is an example of diamagnetic levitation. The little bench that the coil is sitting on top of is solid aluminum. The coil is about three inches in diameter and contains a few hundred turns of magnet wire. A variac is used to drive the coil with AC current.

When the coil is energized, the alternating current creates an alternating magnetic flux. This flux sets up a counter-emf, (electromotive force) in the space occupied by the aluminum plate. This counter-emf creates a current in the aluminum plate that in turn creates a magnetic field opposing the one created by the coil. The two magnetic fields repel and the coil is levitated. Check out the videos and then check out the newspaper article from the '60s describing the levitational stove.

NEW YORK HERALD-TRIBUNE: Monday, November 21, 1951, pp. 1 & 6


In it seven coils of wire on laminated iron cores are contained inside a plywood cabinet of blond mahogany. The magnetic field f…

Superconductor Meissner Effect Levitation

I came across this video illustrating the Meissner effect with a high temperature superconductor from one of my labs today. Pretty fun! Magnetic fields cannot penetrate a superconductor. In order to prevent the magnetic field of the suspended magnet from entering, the superconductor sets up and opposite magnetic field that suspends the magnet.

Groups Made Easy

If you’re taking quantum mechanics, QCD, quantum field theory, electricity and magnetism, or any of the other physics courses where group theory is often used, but rarely explained, then Groups and Their Graphs by Israel Grossman and Wilhelm Magnus is the book for you. It lays out the basics of group theory in simple easy to understand language. For the more esoteric minded, it even covers quaternions.

I just found this book a few weeks ago and finally picked up my own copy. It’s from a seemingly brilliant series of books called the New Mathematical Library that was started in the ‘60s. The series takes advanced or less than common mathematical concepts and explains them in a manner that is targeted at an audience with high school level math skills. Here’s a quote from the book:

"This book is one of a series written by professional mathematicians in order to make some important mathematical ideas interesting and understandable to a large audience of high school students and l…

Understanding Spherical Gradients

Previously we looked at where the 1/r term comes from in the gradient in cylindrical coordinates. This time, we're looking at the gradient for spherical coordinates.

The spherical coordinate values are shown in the figure below. The new theta coordinate is another angular coordinate similar to the phi coordinate introduced in the cylindrical system. It's angle sweeps down from the positive z axis of the Cartesian coordinate system to the negative z axis. Theres a another change. Instead of being anchored on the z axis and moving up and down, the r coordinate is anchored permanently at the coordinate origin.

In this coordinate system, the the angle theta and the radial direction sweep out circles in vertical planes similar to the horizontal plane circles discussed in the cylindrical case. Because of this, the theta coordinate has the same 1/r multiplier discussed in the cylindrical case.

phi and r sweep out circles in horizontal planes exactly as in the cylindrical system.…

Understanding Cylindrical Gradients

We’ve previously looked at how to derive divergence for cylindrical coordinates. If you’re like me though, knowing the rather lengthy derivation won’t help you understand or memorize the resulting formula. So, let’s take a look at why the result makes sense.

The formula for the gradient of a function in cylindrical coordinates is:

Why is the factor of 1/r in the phi term? Remember what question the divergence is asking. We want to find out the amount the function changes vs. a small change in distance along each coordinate’s direction. For coordinates that actually correspond to distances, like x, y, and z of Cartesian coordinates, or r and z of cylindrical coordinates, this is straightforward. The change in the coordinate corresponds to the change in distance along the coordinate.

For coordinates that correspond to angles in the cylindrical coordinate system, there’s an extra twist. The direction of phi always points tangent to a circle centered on the z axis. The small change i…