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.

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

sparky73dx's avatar

roteno's avatar
Victor Laynez @roteno

July Call for Projects! Send links/pictures of your cool projects. One of mine: @eevblog uCurrent for my bench pic.twitter.com/ps9giFTB7x

 

w0sun's avatar
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.

Integrated RF analog, multi-standard, software-defined radio receivers
The scaling of CMOS technologies typically has a great impact on analog design. The most severe consequence is the reduction of the voltage supply. Imec and Renesas have managed to put a complete, high-performance SDR (Software Defined Radio) receiver into a 28nm CMOS process with a 0.9V power supply. The IC has everything except a PLL on a single monolithic chip. (See Figure 1.) This is an impressive integration of analog functionality.

From my Twitter feed: lighting safety, 40m Moxon, diy lead bender

KI4OZG's avatarTracy A Stephens@KI4OZG
Lightning Safety Week: June 23-29, 2013 “When Thunder Roars, Go Indoors!” lightningsafety.noaa.gov/index.htm #hamradio #fieldday

This is a little late, but better late than never…….Dan

 

stahlbrandt's avatarBo G. Stahlbrandt @stahlbrandt
This looks interesting, a 40m Mini-MOXON Beam Antenna by W7XA via @dxzone bit.ly/10EI1T6 #hamr #hamradio

 

DIYEngineering's avatarDIY Engineering @DIYEngineering<
Electronic Component Lead Bending Tool – When assembling a circuit it is pretty common to hook up a resistor or ot… ow.ly/2xBzM7

I still have a lead bender I got from making a Heathkit many moons ago…..Dan

More on the new Heathkit

Heathkit_TM-logo_smallThere’s now a FAQ page on the new Heathkit site. Whoever they are, the new owners sure know how to build up the hype.

Here are a few interesting excerpts:

Big changes, big plans

Q. Is Heathkit back?
A. Yes. We’re back.
Q. So are you really going to make Heathkit® kits?
A. Yes.
Q. Wow! That simple? “Yes?”
A. Yes.
Q. Will Heathkit products include entirely new designs?
A. Yes.
Q. Will you revive any old kit designs?
A. Very likely. Tell us what you’d like – take our survey.
Q. When can I start ordering Heathkit® kits?
A. They’re coming. But it’s a long road, and we need every product we offer to be Heathkit® quality. We will communicate with you, here and elsewhere, as we make progress. Thanks for being patient while we rebuild this great company.
Q. I have great ideas—about products I wish you’d make, and past kits I’d buy if Heathkit brings them back. What should I do?
A. You are our favorite customer. We want to hear from you. Of course, don’t tell us anything proprietary unless you have a non-disclosure agreement signed with us. But if you want to tell us about yourself, your favorite past or future Heathkit product, and what you most hope to see and buy from us: Please—take our survey.

———————————————

Questions about the company

Q. So who are you guys?

A. More on this later. Notwithstanding this FAQ, we’re presently in stealth. But here’s what we want you to know right now: We have enormous respect for the Heathkit® name, and we know you do too. We consider ourselves this decade’s caretakers of the most respected name in do-it-yourself and educational electronics and related products over the past century. It’s a terrific opportunity and a historical responsibility we take seriously, and we want to preserve and grow this opportunity, together with you. We know we need to earn and keep your trust every day. Meanwhile, to whet your appetite: Our new CEO/President, and every member of Heath Company’s Board of Directors, are avid kit-builders and DIYers.  We own and use Heathkit® products ourselves. For those with this interest, it happens we all are licensed amateur radio operators. (Also happy with our team will be: car buffs, pilots, musicians & artists, sports/outdoors enthusiasts, parents, educators, and people who value community service.) Our management team have substantial experience as high-tech executives, in startups and public companies, and in technology and finance. We are carefully growing a team of highly experienced industry advisors. Most importantly, we want you to help and advise us too. Ultimately, it is you, with your excitement and enthusiasm and interest in doing great things with great products, who will make Heathkit a success.

From the trade magazines: spectrum sharing, active filters, real capacitors

Passive components aren’t really so passive (Part 1): Capacitors. Transistors and ICs are considered active components because they change signals using energy from the power supply. Capacitors, resistors, inductors, connectors, and even the printed-circuit board (PCB) are called passive because they don’t seem to consume power. But these apparently passive components can, and do, change the signal in unexpected ways because they all contain parasitic portions. So, many supposedly passive components, like the capacitor shown below, aren’t so passive.

The model above shows that a capacitor adds more than just capacitance when you use it in a circuit.

Peaceful coexistence on the radio spectrum. How two engineers (shown at right) tried to get the military to share some spectrum with their small company.

Signal-chain basics #43: Active filters. While low-frequency filters can be designed with inductors and capacitors, they often require physically large and often expensive inductors. This is where active filters, which combine an operational amplifier (op amp) with some resistors and capacitors, become attractive. Active filters can provide an LCR-like performance at low frequencies