Wednesday, December 30, 2009

Bell Ringers Map

Here is a snapshot of a map (updated 2/18/2010) that includes most of the Bell Ringers who appear on 40 or 75 m.  Click on the image to magnify or to download. In this view I've left off the details of cities and roads to provide a less cluttered view of were our members are located.

The placemarks are defined in a KML file that can display in either Google Earth or Google Maps (for viewing in a web browser). Let me know if you'd like to see a different view or if you want to make some yourself using a copy of the KML file.

Monday, December 28, 2009

Radios with Micromachined Resonators

An article in the December 2009 issue of IEEE Spectrum describes how precision micromachined mechanical components, especially resonators, can provide performance superior to that of electronic components for key functions in wireless handsets (e.g. cell phones).  Two valuable characteristics of such components are:
  • zero or very low consumption of battery power
  • very high Q in resonant circuits (e.g. > 10,000 at 1.5 GHz)
 Dr. Nguyen argues that electronic solutions, including software defined radio designs, are not likely to be practical for wireless handsets due to their requirements on battery power. He points to the presence, in today's cell phone designs, of certain electro-mechanical components:
  • thin-film bulk acoustic resonators (FBARs), 
  • surface acoustic-wave (SAW) resonators, and 
  • quartz crystals.
He predicts that future designs will incorporate MEMS components to overcome the challenges of purely electronic approaches to radio front ends. He reports that handset makers and DARPA are funding work in this area. For additional background on this work, with lots of nice illustrations and article links, visit Dr. Nguyen's web site which includes this link to a research summary.

Sunday, December 27, 2009

Saturday Net on 7230 kHz

The signal reports among participants in the Saturday, 26 Dec 2009 net confirmed the continuing lack of propagation at distances of less than about 250 miles. Without a map in front of me that shows the locations of participants, it is hard to visualize the relative distances and directions among stations. Below is a map view showing the participants' locations and a dark shaded area representing the approximate zone of "no copy" (aka donut hole) relative to Birmingham. Click on the image to magnify.

To represent the ability of various stations to hear each other I produced another view with color-coded lines between many (but not all) pairs of stations. Red signifies good copy and blue signifies poor or no copy. In general, stations that are at least 250 miles apart were able to copy each other, although this distance threshold seemed to be growing as time progressed beyond the 0900 CST start of the net. W4BXI reported poor copy of K9JWJ although they are 307 miles apart. I used purple to mark that path.

Hopefully, this picture will improve as sunspot cycle 24 gets going!

Wednesday, December 23, 2009

Museum of Radio & Technology

Visit the Museum of Radio & Technology in Huntington, WV. Their web site includes:
 A local TV news report provides a brief video tour and commentary on some of the exhibits.

Thanks to W8OI and KA4ZCO for sharing the info about this remarkable museum!

Thursday, December 3, 2009

Antenna Wire Candidates

W4BXI recently shared some samples of antenna wire candidates for review and discussion. I've stripped back the tough insulation on the telco wire types to reveal the conductors and check their wire gauge. Below are photos of the samples, with captions. Click on any photo to magnify.

This first photo shows two similar drop wire types, both with copper-clad steel conductors. Telco #1 appears to be 16 ga, based on my adjustable wire stripper. Telco #2 is 19 ga, based on measurement with a telco wire gauge that has calibrated openings for 19, 22, 24, and 26 ga. The insulation is tough, but manageable with a sharp knife. The copper cladding still looked like copper after my scraping with a knife.

This photo shows two identical or very similar drop wire samples. Both have 2 pairs of 24 ga copper wire. Non-metallic (probably Kevlar) strength members are located near the outside edges of the outer jacket. The wires are located between the strength members. The outer jacket insulation is very similar to the that of the first two samples.

This last photo shows two types of single-conductor stranded wire. #4 has 7 strands of 24-ga bare copper, THHN insulation that is resistant to gasoline & oil. #5 has many strands of tinned copper wire.