## From my Twitter feed: dB, SW, SSTV

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

Jeff Davis @ke9v

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.

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

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.

QSL 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.

## From the trade magazines: satellite tracking, online circuit design, open-source test board

More cool stuff from the electronics engineering trade magazines….Dan

LEO satellite tracking in your backyard. Learn how one guy built his own satellite tracking system in his backyard.

The rise of the online circuit-design collective. Though still in the infancy stage, design and simulation tools that run entirely in the browser are pushing their way onto the EDA landscape. The ultimate goal is that they become essential players within the realm of professional design.

Test and measurement  turns to open source, Kickstarter. The field of test and measurement is set to benefit from open-source software applications if a Kickstarter fundraising project is successful. The Red Pitaya is a credit card-sized, reconfigurable measurement board with 60MHz of input bandwidth and an onboard Xilinx Zinq FPGA to perform signal processing.

## Are you isolated?

There are many times in amateur radio where you want to “isolate” two pieces of equipment or avoid “ground loops.” For example, when connecting a computer to a rig to do digital modes, you should isolate the signals so that there’s no direct connection between the rig and the radio.

What does it really mean to be isolated, though? And, for that matter, what is “ground”?

You can learn what these  terms actually mean and when and why you need isolation if you view the webinar Fundamentals of Signal and Power Isolation. Here’s how they describe the webinar:

This Fundamentals course will briefly look at power isolation (often required in conjunction with signal isolation) and then focus on signal isolation techniques. It will look why it is needed, where it is needed, the relative attributes of techniques for implementing it, and other considerations.

## From my Twitter feed: SDR rx, cool projects, JT-65

Victor Laynez @roteno

Bill WØSUN ? @w0sun

“JT65 – Easy as Pie!” feedly.com/k/1e6pEHI #hamr #Hamradio

## How to build a WWVB receiver?

A recent news story about the 50th anniversary of WWVB got me to thinking about building my own WWVB receiver. I Googled “wwvb kits” and came up with the following:

Unfortunately, all of these kits use a little PC board made by a company called C-MAX, and the company has either discontinued making the IC that powers this module or simply quit selling this module in the U.S. As recently as a couple of years ago, Digikey actually sold this module for about seven bucks.

There are several Web pages that show how to interface the CMMR-6 module to an Arduino or a PIC processor. Here are two:

A couple of companies in the UK seem to still have the modules in stock. The price from a company called Earthshine is only six pounds, but that doesn’t include shipping, of course.

There are some plans that don’t  use the C-MAX chip, but, of course, they’re much more complex. One guy designed his own receiver, but it’s quite a bit more complex than simply using a single chip. There are also several commercial receivers available, but the cheapest one I found is \$220.

There are several Web pages that describe how to use the WWVB receiver modules from “atomic clocks.” One of the projects scavenges the WWVB module from a Sony clock. The second uses the module from an Atomix 13131. The Atomix 13131 costs as little as \$13.

So, I’m still unsure which way I’m going to go here, but it looks as though hacking an existing clock might be the way to go, especially if I can find one at a thrift shop or garage sale.

## From the trade magazines: litz wire, vector network analyzers, SDR

Another selection of amateur radio related items appearing recently in the electronic engineering trade publications.

Litz wire and other component cleverness
If you’re not familiar with it, litz wire is not named after a person or a place. It’s short for Litzendraht, the German term for braided, stranded, or woven wire. It’s a very clever solution to the problems and inefficiencies caused by the skin effect — as the frequency of the current that a wire carries increases, the current tends to go to the outside of the wire.

Vector network analyzers support versatile testing
Among the most valuable of RF/microwave test tools is the vector network analyzer (VNA), which can measure amplitude and phase with frequency. VNAs have long become associated with the measurements of complex impedance parameters—such as scattering (S) parameters—using the test data to design efficient impedance matching networks for the optimum transmission of high-frequency signals through active and passive devices and networks. At present, VNAs are available from both well-known and not-so-well-known instrument manufacturers, in both bench top and portable configurations for making measurements on high-frequency (HF) through millimeter-wave-frequency signals.