CAKE Crumbs Meeting of March 23, 2019

CAKE notes for March 23 2019

No two days are exactly alike at our rendezvous of The Abbey and today it was conspicuously empty. All the usual “heads down in their laptops” were missing, end of final’s apparently. Ron W6WO was joined by Glen KG0T, Fred KJ6OOV, Kerry K3RRY and John N5HPB. At the previous session John amazed us by describing the 3D printer he was building, today it was a laser engraving machine.  This involved constructing a high current DC supply comprising a bank of diodes and power resistors all meticulously designed and constructed as we have come to expect. For hard-to-find parts John spoke highly of Anchor Electronics and Excess Solutions in San Jose. Anyone interested in joining Ron for a field trip??

We had more conversation about PCB layout software including the ability to deal with a variety of components from edge mounted SMA connectors to 0.65 mm parts. Contact Ron if you are interested in such very small capacitors. Fred showed an ARRL book on oscilloscopes which seemed to have most to say about “vintage”analog equipment. However a digital scope from Rigol was described with an attractive price of $350. Fred suspects that with relevant software this scope may become a spectrum analyzer.
A youngish fellow came up and asked if we were Radio Hams (are we so obvious?) then introduced himself as Nick a software engineer involved with geographic data and was familiar with APRS. Nick lives up in the hills so we alerted him to the SLVARC and informed him of their meeting place and time. Fred spent much of our session giving Nick a concentrated tutorial on Amateur Radio and on digital modes in particular. Good work Fred.

Ron posed two mystery items one was the meaning of this string of characters ATC: 100C101JW2500X.  John identified it as an American Technical Ceramics TC100 series 100pF capacitor with a specific tolerance, needless to say this can not fit on a SMD component. It may take some time to realize that either a resistor or capacitor marked as 100 has a value of 10 and one marked as 101 has a value of 100, 102 a value of 1,000  etc. My XYL also has problems with the amount of zeros in a number !
The second mystery was the meaning of the term “Negative Dissipation” which came up in Ron’s  measurement of very small values of the Equivalent Series Resistance of capacitors. One of his measurements had a negative value. Resistors only positively dissipate power, hence the mystery.  Errors introduced in calibration and measurement techniques are known to cause a negative value. This is fully described in an excellent Impedance Measurement Handbook published by Agilent Technologies aka  Keysight. This is available online at section 5-6 . Hint don’t attempt to copy the full 140 pages as many include unprintable labels, at least by my PC/Printer combination.

Here’s wishing you a better information to noise ratio in all you do.

Ron  W6WO

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