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?"