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September 2009 Archive

 

24 September 2009

A tale of two kits ... I ship Z10000 kits and assembled boards by mail. First class mail domestically and to Canada and Air Mail internationally, usually in a size 000 padded mailing envelope. If to the US or Canada, I add a couple of red "First Class Mail" stickers and if international, I use a red "Air Mail" inked stamp on the envelope's front and back.

Early in September, I sent a Z10000 kit to a VE3 ham in Ontario, perhaps 500 miles airline from Northern Virginia. The transit time for this "First Class" envelope was 15 days, representing about 30 miles a day travel. (About the speed before railroads were introduced in the 1840's.) Not long afterwards, I posted a Z10000 kit to a VK ham in Australia, via Air Mail. It arrived in six days after going half-way around the world.

US shipments run between two to four days, depending on distance, although some areas, such as New York and New Jersey are slower than others at the same distance.

The US and Canada are major trading partners´┐Żhistorically Canada is the US's largest export market and vice versa. One would think that mail service between  the US and Canada would reflect that importance. I should add that this is not the first time I've had reports of very slow mail service to Canada, with as long as three weeks delivery time not being unknown. Where the source of delay resides is unknown to me, but delay there is.

 

18 September 2009

I've expanded the conclusions section of my Measuring Distributed Capacitance page to include the caution expressed in Terman's Electronic Measurements over direct SRF determination.

 

11 September 2009

I've added a new page describing six methods of measuring the distributed capacitance of an inductor. The page is Measuring Distributed Capacitance.

 

05 September 2009

I've started collecting measured data on the performance of various capacitor types, a sample appearing below.

The plots below show how a polyester dielectric capacitor behaves with frequency and bias voltage. Polyester is perhaps best known by DuPont's trade name "Mylar." Polyester is popular as a capacitor dielectric, and as the bottom plot shows it has a  very small sensitivity to DC bias, with roughly 2 parts per million change per volt of DC bias, based on my single sample measurement. The capacitance versus voltage measurement presses my HP 4192A's resolution and accuracy, as the change in capacitance for a 70 volt bias swing (from -35V to +35V) is only 0.01%. For almost any practical purposes, we can regard this as a negligible change.

What is not so good with polyester is the rather poor loss (dissipation factor) and the change in capacitance with  frequency. And, neither capacitance nor dissipation factor are stable with temperature.

Other dielectrics, such as polystyrene, are much better in these regards.

 

 
03 September 2009

I've added a new page with impedance (R+jX) measurements of three communications type loudspeakers, including the one used in Elecraft's K2 transceiver. The page may be viewed by clicking here.

 

03 September 2009

As usual, I've moved the August 2009 Updates to an archive page, reachable by the menu at the top of this page or by clicking here.