number 2

CAKE Notes for March 9 2019

The heavy rain did not deter Peter K6UNO or Glen KG0T from joining Ron W6WO at The Abbey.

We discussed the way methods for designing and fabricating Printed Circuit Boards have evolved from crude techniques involving tape and chemicals . Peter spoke highly of KICAD 5.0.2 which is open source software that automates component placement, routing and ordering of components. There are several choices for board fabrication PCB Express being just one of many. Expert help is an advantage to becoming familiar with such powerful software, Peter has found folk at APCircuits very helpful.

We discussed how to handle Surface Mounted Devices (tip: order a few extra as they tend to take wings). Soldering them to a PCB is not as onerous as may be thought. It was generally agreed that working in a good light was important as was using a very fine tip to a temperature controlled iron. A wooden toothpick is popular for holding a component in place. Ron believes that it is of utmost importance to have surfaces clean and preferably those that have been “tinned” in advance. Using a microscope seems to be a personal preference . Even now the simple use of VeroBoard and Dremmel tools is expedient.

Problem solving has also evolved over time and Glen recalls the days of using a “bed of nails” to access test points. Finding problems in software without detailed documentation has probably become more difficult over time. In contrast fixing the loss of network access was simply a matter of locating an obscure on-off switch.

Ron has progressed in gaining knowledge of his Vector Network Analyzer and showed some results from making measurements of capacitors. For those with a VNA here is a simple exercise. After instrument calibration make reflection-mode measurements of resistance and the reactances inherent to your Open-Source-Load standards. My standards are home-brew, so it would be helpful to compare results. Glen asked how can measurements avoid errors due to the resistance incurred by test probes making contact with the device under test. The solution comes from using a technique invented by Lord Kelvin in the 1800s known as the Kelvin 4-point method. This is possible using a two port VNA to measure S21 parameters. Ron will post an image of the technique to Short Skip and provide measurement data in due course.

Better Kelvin picture

On March 6th George Badger W3AB and Ron attended a full day seminar on RF measurements put on by Keysight technologies in Santa Clara, analog and digital topics were presented . Rosenfell detection was mentioned in the context of noise reduction. I note this topic is mentioned in a recent software update for the Anan SDR radio, it (Warren ts) finding out more.about it. Both George and Ron have reasons to make a follow up visit to Keysight. Incidentally the ride in George’s Tesla model 3 was quite intriguing. Imagine driving over the hill in rush hour without having to manually apply the brake.

That’s all for now BCNU March 23 , assume at the Abbey unless other arrangements are selected.

Following the advice of Bob Marley I wish you Positive Vibrations Ron W6WO

 


CAKE  Notes for Feb 23 2019

Our regular “small group” participants  Reed N1WC, Gary K6PDL,  John N5HPB, Kerry K3RRY , Peter K6UNO and Glen KG0T joined Ron W6WO. It was a cool morning which prompted us to sit in comfortable armchairs – comfort at some expense of easy listening.

Gary mentioned the challenge of training VE (Volunteer Examiners) due to turnover of participants. Some of us have a modicum of teaching experience so it could be useful to show  some of the material used in the VE sessions. The demise of Yahoo groups  seems to have encouraged migration to “groupsio”  QRPlabs  is one example.

John never ceases to amaze us with his multifaceted interests and talents- today he described what it takes to find tiny neon bulbs from the 1950s. He found some but only a few were in working order. The group suggested the glass seal had failed releasing the neon gas. Ron related a similar situation where the fluid in a VHS tape-head cleaning product had failed.. Use of a Q-tip to manually clean the heads was recommended. John astounded us once again by his ability to design useful items with 3D printing. Not content with his printer John is now building one of his own design.

Glen is making good progress with his knee surgery and we much appreciate his  effort to take part in our sessions. Glen’s micro-processor Dejour is called Blue Pill (nothing to do with blue-tooth). Glen likes this item as the on-board cost was <$2 shipped, supports Linux and includes a debugger. How about a presentation at a Club meeting Glen? There was some conversation about the history of computer memory and once again the evolution is simply incredible. Adding a 30m element to a 40/80m Butternut vertical came up but we decided to defer discussion. Kerry showed a very cool push button switch with internal colored lights.

Peter is well known as an audiophile and has loaned Ron a copy of an excellent book entitled  “Linear Audio”. It goes to great length to show how audio quality can deteriorate due to power dissipated  in capacitors. At DC and AF these losses are mainly due to the dielectric  material, Polyethylene derivatives are popular dielectric materials. The concerns at audio for power output, efficiency and quality are similar to those at RF but the choices of component technologies can be quite different. Quiz  What typical insulation resistance should be expected in a quality AF/DC capacitor 1, 10, 100, 1,000, 10,000  MOhms ?  What typical Equivalent Series Resistance ESR should be expected in a quality RF capacitor 1,10,100,1000,10,000 mOhms ?

Ron reported some progress in measuring ESR which wastes power in battery- powered devices such as RF beacons and  medical implants. The expected growth of all manner of IOT devices will emphasize the importance of ESR in determining battery life. Incidentally the typical battery in a pacemaker is expected to last about 8 years. How many ampere hours would that be ?   

We discussed a question Don K6GHA had sent in. This concerned the ability to remotely control a relay to switch a single AC power supply between his water pump and crank up tower motor. The group were sure this would be possible but.wanted  more details on what Don was trying to  avoid.

Our next session is on March 9th. which coincides with the Flea-market so we can look forward to some interesting items. 73 BCNU  March 9th   

PS Ron is still looking to share a ride to SJC on March 6th to attend a Foresight seminar on RF,


 

Frank Carrol Jr K6BDK SK,  Bob Perry K6GDI SK

Sadly, two prominent local HAM radio operators have passed away recently.

Frank Carroll, Jr. (K6BDK) passed away in Bend, Oregon on January 26, 2019.  His service will be held Saturday, April 13 at 2pm at the Santa Cruz Memorial Park on Ocean Street Extension in Santa Cruz.  A reception will follow at the Santa Cruz Elks Club on Jewell Street.  Donations in Frank’s memory may be made to the Partner’s in Care Hospice House, Bend, Oregon.  Here is the link to the website: https://www.partnersbend.org/get-involved/donate-to-bend-hospice/

Bob Perry (K6GDI) was a regular voice on the K6RMW repeater, and an active member of the South County ARES and other emergency communications efforts.  He passed away on February 14, 2019, according to his long-time friend Bob Wiser (K6RMW).  No further information is available at this time.

Both will be greatly missed.

73,
Becky
KI6TKB