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Showing posts from November, 2008

Experimental Forest Yagi

This is the three element Yagi I'll be trying out in this week! The guy wires are suspended from trees at each corner. The first set of 'elevation pulleys' allows the ends of the parasitic elements to be raised and lowered independently so that they can be leveled.

The second set of 'tension' pulleys allow the parasitic elements to be removed altogether by lowering them to the ground so that various metrics of the antenna, (gain, impedance, etc...), can be measured with and without them.

Each pulley set is suspended from the guy wires in such a manner that the element can be slid along the guy wire to adjust element spacing.

Plastic and glass string levels are attached to each of the elements and on the cross element level string. The levels are used to make adjustments to ensure that all the elements of the antenna lie in the same plane. The levels are read with a pair of binoculars.

Rockmite 20: Dipoles Really are Bi-Directional

I was back up on Sourdough Trail with the Rockmite 20 on Wednesday. The weather was gorgeous and as long as the sun was out it was warm enough to shed a few layers. I ran into a few dove as I hiked up out to the end of the ridge, but the resident moose must have been hiding out.

I hung the dipole between two trees at the point of a ridge line that points off to the East at an altitude of 10,200 feet. The antenna was oriented just a little bit to the northeast due to the positioning and availability of suitable trees for antenna supports.


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KD0FNR station location and antenna orientation Antenna support























After CQing for awhile, I was rewarded with a callback from KB8AP in Central Point, OR who provided me with an RST report of 439 while I could read him at 239, RST reports being rather subjective things with the Rockmite since it has no S meter. After we chatted for a bit, I CQ'ed again and immediately heard back from KC8ITC in the opposite direction, Saline, Michigan w…

Ham Radio University 2009 at Briarcliffe College, Bethpage, NY

I just heard about a very cool event today, Ham Radio University. If you're going to be near Bethpage,NY on January 11, 2009, then you should stop and check it out! This event is all about learning, seeing, and doing. The event announcement says:

There will be forums about everything from satellite communications, low power operating using radios as small as a tuna tin and the latest in emergency communications. There will also be a VE session for those who would like to take an FCC exam and Special Event Station W2V set up and operational on HF. Go check it out! It sounds like a lot of fun!

Google Gadgets from Copasetic Flow: Scientific Caclulator

It occurred to me while developing the ham radio practice exams, (Technician, General, Extra, Canadian Basic), that it would be handy to have a scientific calculator available on the same web page as the exam. Google provides a framework that allows applications, (called Google Gadgets), to be deployed on any web page. I looked into available Google Gadgets that fit the bill, but none of them provided the features and the form factor required for the practice exams. So, the Copasetic Flow scientific calculator was created:



If you'd like to install the calculator on your own web pages, just pick up the code on the Google Gadgets Catalog.

The Rockmite Breaks 2000 Miles Per Watt!

Yesterday, I hiked South along Sourdough Trail, near Ward, CO, to a little clearing that looked out from the Eastern slopes of the Rockies. The altitude is about 10,000 feet and the view of the foothills and plains below is striking! With the half-wave dipole antenna up between two trees, (about 11 feet high on one side and 7 feet high on the other), I began to call CQ. Before long, N8JIW called back with a QTH of Cleveland, OH and an RST report of 229! Cleveland is over 1200 miles from my little clearing! The 20m Rockmite outputs 500 milliwatts. That works out to more than 2400 miles per watt on a CW QRP QSO!

The trails up around Brainard Lake and the Red Rock Trailhead are beautiful and very accessible right now! There's just a little bit of snow since we haven't really got our first big storm up here yet this year. I ran across two hearty folks that were camping overnight along the same ridge with their dog. As nice as it is right now, the wind can still come up une…

The Rockmite 20 at 10k

The Rockmite is back up and running! After replacing the 2N2222 that amplifies the transmitted signal I hadn't made a contact in a week or so, and I was starting to think I'd smoked yet another component. I decided maybe a better antenna location would help. The weather was exceptionally warm in Boulder today, so it seemed like the perfect time for a hike. I packed up the rig, my fishing pole, and my antenna and headed for Lefthand Reservoir in the Roosevelt National Forest outside Ward, CO.



The temperature was quite a bit colder at altitude, (Lefthand lies at about 10,700 ft.), but the hike was pleasant and pretty easy. There's not a whole lot of snow yet and the trail to Lefthand lies entirely on a Forest Service Road that's closed for the winter. The reservoir was completely frozen over, so fishing was out, and I set up the Rockmite and its antenna right away.


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I hung the half-wave dipole about six feet up to start, turned on the Rockmite, and heard…

Industry Canada Basic Qualification Amateur Radio Practice Exam

Subelement Focus Added to Amateur Radio Practice Exams

Go take a practice test now using the links below!
Technician
General
Extra

Read the review of the Copasetic Flow Ham Radio Practice Tests at kb6nu.com

The next time you practice a ham radio licensing exam here, you'll notice that the interface has changed a little bit to add a few new features.

Focused Practice on Subelements
Taking practice exams that simulate the randomly selected exams used for license tests is one of the best ways to study. But, sometimes, there's just one section of the test that is giving you the most trouble. Now, when you click the 'Practice Subelements' button, a control panel will appear that allows you to restrict your study to a single test subelement.


When you click on the button for a subelement you will only be presented questions from that subelement. The button for the subelement you've selected will be highlighted with a different colored background.

After you've studied the subelements you wanted to focus on, just click 'Prac…

The Brachistochrone Expanded and A Few Qeustions

This installment of “It’s Obvious. Not!” looks at:

Book: “Classical Dynamics of Particles and Systems”

Edition: third

Authors: Jerry B. Marion and Stephen T. Thornton

Publisher: Harcourt Brace Jovanovich

Pages: 176-178 (Chapter 5, Example 5.2)

Reading physics books, it often occurs to me that the authors must be aware of some patterns or 'rules of thumb' that the reader may not be privy to. Today's post expands a very truncated example from Marion and Thornton and hopefully clarifies it. This post also poses several questions in search of those patterns and rules mentioned above.

After explaining the calculus of variations and the importance of Euler's equation
Marion and Thornton follow up with a concrete example: the brachistochrone. The problem of the brachistochrone is to determine the path for a particle to move from point A to B under the influence of a constant force, (gravity for example), in the least amount of time. The 'least amount of time' phrase shou…

Casing Up the RockMite

My RockMite 20 is safely ensconced in its Leatherman box today. I know the typical enclosure is an Altoids tin, but I've had the Leatherman tin sitting in a closet since last Christmas just waiting to be used for something. It saved me the cost of a box of Altoids and gave me plenty of room to work with. The extra room was nice since this is my first enclosure project in about fifteen years.

The extra space in the box also gave me plenty of room to install my KD0FNR/Panasonic iambic keyer, and the large lid makes for a nice hand rest while keying, more on that later. If you remember from last time, rather than going out and purchasing a keyer, I went with the quick fix of snapping a few switches off an old TV I recently took apart. One of my favorite sayings is 'I'd rather be lucky than smart.' When I tried to snap two switches off the TV's control panel, I came up with three instead. As usual I lucked out! I hadn't been thinking about the mode switch fo…

The Calculus of Variations and Hamilton's Principle from the Top Down

This installment of “It’s Obvious. Not!” looks at:

Book: “Classical Dynamics of Particles and Systems”

Edition: third

Authors: Jerry B. Marion and Stephen T. Thornton

Publisher: Harcourt Brace Jovanovich

Page: 172-177

Chapter Five in the third edition is titled "The Calculus of Variations" The book does a great job of giving a very detailed bottom-up derivation of Euler's equation and a second form of Euler's equation. I had a much easier time with the material once I figured out that Euler's equation was actually the goal of the derivation and how Euler's equation is used. Since the top-down view made things simple for me, I decided to post it here for other top-down thinkers.

Chapter five is simply building a set of tools to be used in chapter six with regard to Hamilton's Principle and Lagrangian mechanics. So, maybe the first question should be, 'Why are Hamilton's Principle and Langrangian mechanics important?'

Newtonian Mechanics essentially…

RockMite Up and Running! Hello Oak Harbor Washington!!!

I finished populating the RockMite board. Construction of the entire kit was amazingly easy, even the little bit about grounding the crystal cases which I expected to be a pain.

Fully Populated RockMite

Crystal Case Grounding

I added the connectors from the connector kit, set the radio up on its smoke bench and took a listen. Last night, here in Boulder, I couldn't hear a thing so I tried again this morning. As the sun got up over the horizon, there were first a few and then plenty of CW signals coming in!!!

Smoke Bench


Once I realized their were hams on the air, I started casting about for a makeshift Iambic keyer. I gave away my straight key along with my radio about five years ago. I recently gutted an old TV and had pulled out a strip of front panel buttons. I broke off three of them, (I was trying for two, but three came out), and tacked them onto the key plug for the RockMite to create the KD0FNR/Panasonic Iambic Keyer:












I listened for a bit and heard W9FFU calling CQ. I ban…