From my Twitter feed: bad soldering, tequila,

hackaday's avatarhackaday @hackaday
New post: Impersonating FBI Agents And People Who Can Solder bit.ly/JQRKil

2e0sql's avatarPeter Goodhall @2e0sql
Interesting talk on using NodeJS and websockets within Amateur Radio specially when using hardware.- youtu.be/r0svcHERWrM #hamr

NS0D's avatarPete NSØD @NS0D
The #Arrl Centennial QSO party starts 1-Jan-2014 – should be a real marathon with a few different awards available arrl.org/centennial-qso…

This isn’t related to ham radio, but I do like a nip of tequila from time time….Dan

Gizmodo's avatarGizmodo @Gizmodo
How tequila geniuses made the best-tasting spirit I’ve ever had: gizmo.do/qo176k0 pic.twitter.com/XAoQTSrcCz

From my Twitter feed: bypass caps, VHF propagation, SMD rework

dangerousproto's avatarDangerous Prototypes @dangerousproto
app note: properties and application of bypass capacitors goo.gl/YFpqLx

georgesmartuk's avatarGeorge Smart @georgesmartuk
Not sure if everyone has seen @ng0e‘s fantastic VHF Propagation Map from #APRS data. How genius! aprs.mountainlake.k12.mn.us #hamr #hamradio #vhf

DIYEngineering's avatarDIY Engineering @DIYEngineering
app note: Rework method for surface mount MLCCs – Things you might need to know about doing SMT rework on Multi La… ow.ly/2C95Qu

From my Twitter feed: learn electronics, visualize cellphones, NTS newsletter

 

imabug's avatarimabug @imabug
LearnAbout – Electronics learnabout-electronics.org/index.php

 

TheZerocool's avatarDenis S @TheZerocool
If your in the school of thought that mobile phone mast RF will cook your mind… check this out and begin to worry: goo.gl/XcrkAN

 

VA3QV's avatarBob Sharp @VA3QV
A link to a NTS Themed Newsletter : ve3gna.wordpress.com/2013/12/07/lat…

Transforming impedances: Question G5C07

In the last two weeks, I’ve received e-mails from two readers of The No-Nonsense General-Class License Study Guide. Both questioned my explanation of how transformers transform impedance. I wrote:

Transformers are also used to transform impedances. The impedance ratio is also related to the turns ratio, but the transformation is equal to the square of the turns ratio. The turns ratio of a transformer used to match an audio amplifier having a 600-ohm output impedance to a speaker having a 4-ohm impedance is 12.2 to 1. (G5C07)

Doug wrote, “The only way I can reproduce the calculation is by taking the square root of the turns ratio.” His comment made me see where my explanation could be a bit misleading. I wrote back:

Think about it this way. An impedance transformation can go either way. When transforming from a higher impedance to a lower impedance, you divide by the square root of the turns ratio. When transforming a lower impedance to a higher impedance, you multiply by the square of the turns ratio. In either case, the impedance ratio is “related” to the square of the turns ratio.

I love getting feedback from my readers. Feedback like this helps me improve my study guides. If you have used one of my study guides, and have a comment or question about any of the material, please feel free to contact me.

EE Times on PCB design

Are you interested in designing your own printed circuit boards (PCBs)? Then EE Times has a couple of things that you’ll be interested in:

  • Webinar: Fundamentals of PCB Design. This free, introductory overview of printed-circuit design treats the main difficulties you will likely meet when planning, designing, and manufacturing printed circuit boards for digital applications. From this lecture you will take away many nuggets of wisdom concerning manufacturing technology, signal integrity, EMI, power quality, thermal analysis, and project management.
  • A Guide to Low-Cost PCB Tools. This short blog post, written by Adam Carlson, Senior Mechanical Design Engineer, Eagle Technologies, lists eight different PCB design tools that are available for free or are low cost.

If you’re already doing your own PCB design, what tools are you using?

From my Twitter feed: dB, SW, SSTV

EDNcom's avatarEDN.com @EDNcom
Engineers refer to measurements in dB all the time. Here’s a refresher on decibel basics. edn.com/design/test-an…

 

ke9v's avatar

Jeff Davis @ke9v
Radio World: Shortwave Efficacy to Be Pondered at BBG radioworld.com/article/shortw…

 

AMSAT_UK's avatar

AMSAT-UK @AMSAT_UK
ISS Amateur Radio Slow Scan TV Active wp.me/p2Mn4x-4Yk #amsat #hamr #iss #sstv

From my inbox: silent Sun, hacker’s paradise, NY Maker Faire

The sun that did not roar. This is the height of the 11-year solar cycle, the so-called solar maximum. The face of the Sun should be pockmarked with sunspots, and cataclysmic explosions of X-rays and particles should be whizzing off every which way. Instead, the Sun has been tranquil, almost spotless.

Guest Rant: Ham Radio — Hackers’ Paradise. Bill Meara of SolderSmoke on why ham radio is a hacker’s paradise.

Maker Faire: When will we make cars and phones at home? The BBC covers the recent New York Maker Faire.

 

 

 

Video: Radio & TV careers, regen radio, WWV

Your life work series: radio and television (1940). If this was 1940, this video would show you how to get into the radio and television business.

One-transisitor regen receiver. This video shows you how to make a simple one-transistor AM radio.

WWV: All the time, all the time. What more is there to say? (Courtesy Brad, AA1IP and the Glowbugs mailing list)

A new way to teach Ohm’s Law?

I’ve been trying to come up with some short videos that I could post on YouTube that would go over the same material that I do in my one-day Tech classes. In my classes, I basically teach the answers to the questions, but I also try to give a little bit of context, so that they get some idea anyway of the bigger picture.

I start out with the day with electrical principles. That means talking about questions in section T5. Obviously, Ohm’s Law is a big part of section T5. So, I searched YouTube to see what other videos are already out there that explain Ohm’s Law.

In doing this, I ran across a video by a guy named Daniel Sullivan. Apparently, he teaches classes for electricians and industrial technicians. Here’s his video, “Teaching Ohm’s Law to Techs – Part 1″:

One of his main points is that we shouldn’t use the notation E, I, and R when talking about Ohm’s Law. Instead, he says, we should use the notation V, A, and ?. These are, after all, the symbols that we use to denote the units of voltage, resistance, and current, and the symbols that  you see on a meter. If you buy that logic, then the answer to question T5D01 which reads:

What formula is used to calculate current in a circuit?

should be:

Current (A) equals voltage (V) divided by resistance (?).

The more I think about this, the more I like it, and I’ve just e-mailed the Question Pool Committee to see what they think about this. I’d like to know what you think, too.

CQ’s “ham shop”

I like to look through the ads and classified ads in the back of ham radio magazines and find items that I haven’t seen before. Since I just re-subscribed to CQ Magazine, I thought I’d scan the ads there. They call their classified ad section “ham shop.”

Breadboard Radio. Breadboard Radio sells a couple of small kits including the Splinter QRPp Receiver/Transmitter ($55), the Toothpick Audio CW Filter/Amp ($25), and the Sawdust Regen Receiver ($25). One cool thing about these kits is that you get a base onto which the PC board mounts. The audio filter or the regen receiver might make a good first kit.

MaineStore.Com. Name tags, belt buckles, coffee mugs, Christmas ornaments, and more, all personalized with your callsign are available from MaineStore.Com.

w8die_50QSL Cards From the Past. W8JYZ has built a collection of more than 43,000 QSL cards dating back to the 1920s, and he’s scanned many of them and put them online. As far as I can tell, he’s doing this just to preserve our ham radio history. This is a great website. There are a lot of QSLs from stations whose callsigns spell words, like the one at right.

One thing that I found kind of odd is that a couple of the ads there contained links that no longer worked, including www.hamradioprints.com and www.vintagehamshack.com. I guess the proprietors of these websites paid for their ads in advance, but have since gone out of business.