CAKE Notes for April 13 2019
Glen KG0T, Peter K6UNO and Ron W6WO met in comfort at the Abbey. The close-knit trio provided an opportunity for some intense discussions.
Glen is now well known for the breadth and depth of his knowledge in the field micro processors . The word “field” seems quite appropriate as they seem to be appearing like mushrooms. Glen brought seven types mounted on a breadboard and proceeded to describe how they compare in terms of speed, languages, ease of development and system software. The one item they had in common was their purchase cost being in single digit dollars. Ron commented that in his case the cost of programming labor would be prohibitive. Glen hinted that he was developing a presentation on uProcs to deliver at a future SLVARC meeting. Stay alert for details
Peter returned to a previous CAKE topic of software for printed circuit board (PCB) layout and fabrication. Peter showed a recent book on KiCAD -pro which is evidently a powerful well documented product. More details can be found on txplore.com and a PCB fabrication firm called OSHPark.
Peter asked how Ron’s VNA exercise was pr proceeding. The best way to respond is to quote Lao-Tzu (a 6th century Chinese philosopher and writer). “The further one pursues knowledge- the less one knows” In this instance all was going well until my home-brew short circuit calibration standard was measured giving the result of 0.0007 Ohms. A value of 0.007 would have been cause for celebration as it indicates a precision needed to make accurate ESR measurements- however one extra zero seems unealistic and suggests all is not well.
Glen posed one of his insightful and deceptively simple questions -”what makes a VNA the instrument of choice for measuring impedance ?”Leaving aside the question of accuracy my best answer is that it combines all the needed elements of a programmable signal source having precise frequency and phase , a vector voltmeter, phase sensitive detection, analog-digital conversion and digital signal processing together with a comprehensive graphical user interface.That said even high-end Rhode and Swartz VNAs have trouble measuring capacitor ESR.
A VNA provides the same degree of dynamic range, precision and upgrade potential which makes a SDR the choice for Amateur communications. The VNA I made was designed by true experts N2PK and G8KBB who have a high regard for entry level users while satisfying the professional demands of others. Our conversation included some terminology relevant to VNA measurements such as reflective loss and dissipation loss .
At his point in time I would like to inform all readers that I am about to leave the area for my annual trek to GA and KY with a possible side trip to the UK ( while it stillhas the U ) with an open ended return date, most likely in August
73 all round Ron W6WO