TECHNICAL TOPICS AND INFORMATION[i]

 

Imagine a CW "dit" that lasts for just a femtosecond! And it's not even the start of the NA Sprint! No contests are yet scheduled in the wide swath of Terahertz spectrum between millimeter-wave and infra-red, but researchers are begin to explore applications for those signals. This story <http://www.physorg.com/news147361232.html> from Physorg.com discusses how THz waves interact with matter and how they are likely to be used initially. We're already using radio at frequencies that were "science fiction" not long ago, so stay tuned for interesting developments at 300 GHz...and beyond!

 

Pat W7TMT directs us to the Web site of K7MEM <http://www.k7mem.com/> that offers a variety of on-line calculators. Amongst them is a calculator that allows you to calculate the required inductance and dimensions for each side of a loaded dipole based on coil position. It also includes several ways to generate details for winding the coil itself based on diameter, L/D ratio etc.

 

One ham-radio spinoff of the surging development of electric cars is the improvement in the energy storage capability of batteries. This Technology Review article <http://www.technologyreview.com/energy/21750/?a=f> discusses one such improvement, increasing the surface area of battery electrodes by using "nanoporous silicon". Field Day and hilltopping can only benefit!

 

Paul WY7I's Colorado QTH is featured on the cover of the RSGB's December RadCom. Just the thing for the holiday season! (Photo WY7I)

 

Here's a problem we should all have - a too-tall tower! Actually, these can be a problem to use as 160 meter verticals, but you might be able to feed the tower using elevated, sloping radials. This arrangement is described in Tom N4KG's article in the June 1994 /QST/. The article also lists some good references. (Thanks, Chas N5UL)

 

When adding equipment to the shack (does anyone ever REMOVE equipment?) it's often necessary to also add a shelf or stand. If you go to the office supply store, you can find itmes designed specifically for electronics and computer equipment, but they tend to carry premium prices. A less expensive source may be your local department store's "Housewares" aisle. For example, the local Wal-Mart had plastic 6"x6" "mini-crates" for $1 that could be easily glued together into a very nice platform with storage. Nearby were plastic sets of drawers - good for adaptors and stuff - for a few dollars more. Craft stores are also great sources of volume-priced stuff that does just fine in the shack.

 

A short "gift" item in the November IEEE Spectrum <http://www.spectrum.ieee.org/nov08/6916/6> caught my eye - the observation that within each 9 V battery are six 1.5 V AAAA cells. These cells are a little shorter than AAA's and those inside the 9 V package aren't labeled for polarity, but in the time-honored tradition of ham frugality, these cells can be put to work in various low-power applications.

 

Bob W6TR recommends the Web site of Matthew KK5DR <http://www.kk5dr.com/> for information on amplifiers - building them, testing them, designing them. And the site is definitely packed full! I found myself browsing quite a few of the site's articles and thinking, "You know, I should build an amplifier..."

 

Another resource for amplifier builders can be found in past issues of Ham Radio. Bill Orr W6SAI-SK wrote a series of articles entitled, "Design Considerations For Linear Amplifiers," in the June, July, and August 1979 issues. The basics in these articles still applies and would come in handy to amplifier builders. It was also published as Eimac's Amateur Service Bulletin AS53. (Thanks, Eddy VE3CUI/VE3XZ and Peter G3RZP)

 

Paul K5AF sends this method for making a cheap lightweight mast, "Use the thinnest schedule PVC pipe you can find, buy a can of "Great Stuff", make a telescoping mast about 28' long with three diameters of PVC, drill a small hole every foot and shoot the Great Stuff in, let it harden and you have a very rigid mast for Inverted-Vees and other wire antennas. If you wish, you can even embed ladder line in the mast before you shoot the foam inside, from what I can tell, Great Stuff has pretty decent dielectric properties."

 

When rebuilding or refilling an oil-cooled dummy load, such as a Heath Cantenna or MFJ-250, be sure to use the manufacturer's recommended type of oil. Mineral oil can be obtained from feed stores or aircraft maintenance facilities. Transformer oil is a little less common, but can be ordered by the gallon from MFJ Enterprises <http://www.mfjenterprises.com/Catergories.php?sec=25>. (Thanks, Bob N7XY and Roger K8RI)

 

Ed W2RF is developing a CW Skimmer application called RigSync <http://www.ehr.net/w2rf/download/rigsync0100.msi> that integrates output from the automated decoder with the WriteLog logging software. RigSync works with both Windows XP and Vista.

 

Besser Associates has published a neat on-line Smith Chart applet <http://www.bessernet.com/jobAids/jSmith/jSmith.html>. You can build a circuit, including stubs, and see impedance transformations take place on the chart. Fun for practice!

 

If you have AM broadcast stations anywhere in your vicinity, tuning low-band antennas can be a real pain as the AM energy can be strong enough to upset the measurement circuitry of many SWR analyzers. This is discussed in the article "Tips for Tuning a Full-Size 160 Meter Vertical" by Jay WX0B in the Nov/Dec issue of National Contest Journal <http://www.ncjweb.com/> magazine. Jay recommends a W3NQN broadcast band reject filter - the schematic for this filter can be found in the /ARRL Handbook/. Jay also notes that external filters add phase and amplitude effects to signals passing through them and these effects must be accounted for in the measurements.

 

*Technical Web Site of the Week* - Gee, how can you go wrong with a company named United Nuclear <http://www.unitednuclear.com/>? Through the Make magazine <http://makezine.com/> newsletter, I found out about this cool company that has a little bit of everything for the scientific hobbyist, teacher, or bright young person. The lab supplies section is an endless browse - I want a cork boring machine! And you'll love the animated graphic that asks, "Looking for some Uranium?"

 



[i] items from the ARRL Contest Newsletter 12/9/2008