From my Twitter feed: SDR, spider coils, smart scope

vielmetti's avatarEdward Vielmetti @vielmetti
decoding radio digital modes without a radio, using WebSDR and fldigi /cc @kb6nu #hamr bit.ly/1o678qG

mike_n8wc's avatarMike Comer @mike_n8wc
@kb6nu great info! Back to radio after several years. Enjoy how the internet has enhanced enjoyment of a great radio hobby.

AK6L's avatarRobert Liesenfeld @AK6L
Taught myself PostScript and wrote a template generator for making spider-wound coils. Inspired in part by .@vk2zay. github.com/xunil/spider_c…

DH1TW's avatarTobias @DH1TW
“SmartScope – Kickstarter campaign for an open source 100MS portable oscilloscope #hamradio #diy feedly.com/k/1gr8jQm

LC100 LC meter seems like a good deal

I recently bought an LC100A LC meter from eBay, like the one shown below. If you search eBay, you’ll find them on sale anywhere from $20 to $40. Yesterday, I finally got around to playing with it a little.

lc100

To power the device, you need to supply +5V. It comes with a cable that has a USB connector on one side and a power connector on the other. Obviously, it’s meant to be powered by a USB port. I used a power adapter that I purchased to charge an iPod. It worked great.

As a quick test, I measured the capacitance of ten 0.33 uF caps that I purchased for a project. I first measured the capacitance with the LC100A and then with the fancy-schmancy Keithley 2110 that I purchased about a year ago. Below are the results:

LC100 2110
1  .35 .339
2  .33 .326
3  .33 .318
4  .33 .322
5  .33 .324
6  .34 .328
7  .34 .330
8  .34 .329
9  .34 .330
10  .33 .316

Now, this wasn’t a very scientific test, but I am pleased with the results. I also measured the value of some 330 uH chokes that  I had. They all measured between 315 and 320 uH.

So, all in all, I think this is a good deal for the money. I’m looking forward to using it on some of my projects. The next step is to find a box to put this in. I’m surprised that no one seems to have found one yet.

2014 Tech study guide: Basic repair and testing

The addition of T7D12 is the only change to this section…Dan

The most common test instrument in an amateur radio shack is the multimeter. Multimeters combine into a single instrument the functions of a voltmeter, ohmmeter, and ammeter. Voltage and resistance are two measurements commonly made using a multimeter. (T7D07)

You use a voltmeter to measure electric potential or electromotive force. (T7D01) The correct way to connect a voltmeter to a circuit is in parallel with the circuit. (T7D02) When measuring high voltages with a voltmeter, one precaution you should take is to ensure that the voltmeter and leads are rated for use at the voltages to be measured. (T7D12)

An ohmmeter is the instrument used to measure resistance. (T7D05) When measuring circuit resistance with an ohmmeter ensure that the circuit is not powered. (T7D11) Attempting to measure voltage when using the resistance setting might damage a multimeter. (T7D06) What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time is that the circuit contains a large capacitor. (T7D10)

An ammeter is the instrument used to measure electric current. (T7D04) An ammeter is usually connected to a circuit in series with the circuit. (T7D03)

In addition to knowing how to make electrical measurements, knowing how to solder is an essential skill for amateur radio operators. Rosin-core solder is best for radio and electronic use. (T7D08) A grainy or dull surface is the characteristic appearance of a “cold” solder joint. (T7D09)

2014 Tech study guide: SWR and antenna measurements

In the 2010 study guide, this section was part of the section on feedlines and connectors. I think it makes more sense to separate it like I have here. There is one added question in this section T7C13 asks what a dummy load consists of…Dan

Standing wave ratio is a term you’ll often hear when talking about antennas and feedlines. In general terms, standing wave ratio (SWR) is a measure of how well a load is matched to a transmission line. (T7C03) In this context, the “load” is the antenna. When we say that an antenna is matched to a transmission line, we mean that the impedance of the transmission line is equal to the impedance of the antenna.

The reason it is important to have a low SWR in an antenna system that uses coaxial cable feedline is to allow the efficient transfer of power and reduce losses. (T9B01) The bigger the mismatch is between the feedline and the load, the higher the SWR will be, and the more power you will lose in the feedline. Power lost in a feedline is converted into heat. (T7C07) Power converted into heat is not radiated by the antenna, meaning your radiated signal will be weaker.

You can measure the SWR of your antenna system with an SWR meter. You usually connect the SWR meter near the output of your transmitter because it is important to have a low SWR at that point. A directional wattmeter is an instrument other than an SWR meter that you could use to determine if a feedline and antenna are properly matched. (T7C08)

1 to 1 is the reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline. (T7C04) 2 to 1 is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power. (T7C05) An SWR reading of 4:1 means that there is an impedance mismatch. (T7C06)

One way to ensure that the impedance of the antenna system matches the output impedance of transmitter is to use an antenna tuner. An antenna tuner matches the antenna system impedance to the transceiver’s output impedance. (T9B04)

In addition to the SWR meter and the directional wattmeter, there are a couple of other types of test instruments commonly found in an amateur’s “shack.” One instrument that every shack should have is the dummy load. A dummy load consists of a non-inductive resistor and a heat sink. (T7C13) The primary purpose of a dummy load is to prevent the radiation of signals when making tests. (T7C01)

Another common test instrument is the antenna analyzer. An antenna analyzer is an instrument that can be used to determine if an antenna is resonant at the desired operating frequency. (T7C02) You can also make a number of other measurements that will help you set up an antenna system, such as SWR, capacitance, and inductance.

From my Twitter feed: radio gifts,

RadioSurvivor's avatarRadio Survivor @RadioSurvivor
There’s got to be someone on your list who wants a radio purse radiosurvivor.com/2013/12/02/hol…

Check out the radio tower tie….Dan

HamRadioSupply's avatarAmateurRadioSupplies @HamRadioSupply
New post: What the heck is a grid dip meter? goo.gl/C9BTnR

I wrote this yesterday for the AmateurRadioSupplies.Com blog…Dan

ARRL_PR's avatar

ARRL Media & PR @ARRL_PR
Get tips on #HamRadio PR & promotion! The December issue of #ARRL‘s CONTACT! has been posted! bit.ly/bRzdks

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.

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: no code test, Contest U, iPhone sig gen

Jeff K1NSSJeff K1NSS @K1NSS
NO CODE TEST! If that don’t grab ‘em, I argue MIGHT AS WELL! Outreach according to http://www.dashtoons.com  #hamr #qrp pic.twitter.com/vAngtDNmmu

Matt MaszczakMatt Maszczak @rocknrollriter
For the new or newer op looking into contesting: http://www.arrl.org/news/view/dayton-contest-university-videos-available-on-youtube?utm_source=twitterfeed&utm_medium=facebook …

Jacob BeningoJacob Beningo @Jacob_Beningo
Turn a Smart Phone into a Signal Generator | EDN http://www.edn.com/electrical-engineer-community/industry-blog/4416138/1/Turn-a-Smart-Phone-into-a-Signal-Generator … via @edncom

From the trade magazines: capacitors, inductors, radio architectures

Temperature and voltage variation of ceramic capacitors. Read the data sheet! This tutorial explains how ceramic capacitor type designations, such as X7R and Y5V, imply nothing about voltage coefficients. You must check the data sheet to really know, how a specific capacitor will perform under temperature and voltage.

Circuit measures capacitance or inductance. You don’t need a fancy LC meter to measure capacitance or inductance. This short article show you how to do it with a function generator, multimeter, frequency counter, and an oscilloscope. Hmmmmm. By the time you get that all lashed up, it might have been quicker to just buy one of these LC meters from China.

Understand Radio Architectures. This is the first in a series of excerpts from the book RF Circuit Design, 2e by Christopher Bowick. Even though this appears in an engineering trade magazine, some of this is pretty basic stuff. You even get a schematic for a crystal radio!