Learn about ISM radio

November 27, 2012 by Leave a Comment

Found this in my inbox this morning. We share some frequencies with the ISM service, including about 1.5 MHz in the 440 MHz band. That being the case, it might be  good idea to learn something about ISM.

Design News continues with the Digi-Key Continuing Education Center Track, “ISM Band Radio.”

Register for this track!

Each day the first 25 people who attend will receive a $5 Starbucks Gift Card.*

ISM Band Radio
December 3 – 7, 2012
11 am PST / 2 pm EST

ISM Band Radio features guest lecturer Paul Nickelsberg, President and Chief Technical Officer of Orchid Technologies Engineering & Consulting Inc. Mr. Nickelsberg has over 30 years’ experience as a technical innovator and problem solver.

  • Dec. 3: Radio Communications Range & Regulatory Matters
  • Dec. 4: 802.15.4 Radio Link Modulation
  • Dec. 5: 802.15.4 Radio Protocols & Topology
  • Dec. 6: 802.15.4 Radio Power Requirements
  • Dec. 7: 802.15.4 Transceivers in Commercial Components – Fall 2012

Register Now for all five courses and share this opportunity with your network. Check out the schedule for other tracks of interest.

Filed Under: Gear/Gadgets

DMM tips, anyone?

November 25, 2012 by 8 Comments

Now that I’ve published the No-Nonsense Extra Class License Study Guide, I’ve been thinking about what my next book should be. At this point I’m leaning towards The No-Nonsense Guide to Digital Multimeters. I have even started outlining the book:

  • What is a digital multimeter?
    • Compare to analog multimeter
  • Digital multimeter basics
    • Measurement types
    • Inputs
    • Range
    • Zero
    • Safety
  • Making measurements with a DMM
    • Simple DC circuit
      • voltage
      • current
    • AC measurements
      • true RMS
    • Resistance
  • Tips for Choosing a DMM
  • Hints and Kinks

I’d love to get your feedback on this.

What else should I add to this outline?

What would you like to know about DMMs?

Do you have any tips for using DMMs that you’d like to share with others? (If I use your tip in the book, I’ll send you a free copy when it’s finished.)

Filed Under: Books and Magazines, Test Equipment

REVIEW: Wouxoun KG-UVD1P 2m/440 HT

November 23, 2012 by 4 Comments
Wouxoun KG-UVD1P

Is this radio worth $93? Read the review.

Normally, I hate spam, and when I find it in my inbox, I mark it as such, and attempt to unsubscribe, if there’s a link to do so. Even so, sometimes, when the spam is amateur radio related, I’ll take a peek. So, even though I hate to admit it, I did succumb to some spam last week.

The spam was an e-mail from Amateur Radio Supplies offering me 7.3% off my next purchase. I had never heard of Amateur Radio Supplies before, so I decided to click over to their website and see what they had for sale.

Most of the stuff they sell is pretty unremarkable. There’s a lot of MFJ stuff and some Alinco radios. What caught my eye, though, is that they were selling the Wouxoun KG-UVD1P HT for $100. With the 7.3% discount, that price would be $92.70. I Googled around a bit, and the lowest price that I could find elsewhere was $112, so I decided to buy one for myself and play around with it for a bit.

The radio arrived within a week, and I eagerly unpacked the radio. I hadn’t bought a new, in-the-box radio in years. It was all very nicely packaged, and came with a wrist strap, desk charger, and rubber ducky antenna.

I clipped the battery pack onto the radio and turned it on right away, even though the battery really needed charging. The first thing I noticed was how bright and easy-to-read the display was. I also got a chuckle from the voice that came out of the radio announcing that it was in frequency mode. The voice is female, and while the announcement was in English, it had a very distinctive Chinese accent.

At that point, I turned off the radio and set up the charger. I came back that evening, to find the battery fully charged. I’m not sure how long it took, but it definitely charges pretty quickly.

The next step was to set up some frequencies. I had heard this was very difficult to do, but I didn’t find it to be so tough, especially once you get the hang of how to work the menus. Without too much futzing, I was able to program the two repeaters that I use most. I was aided in this by the relatively decent user manual and the quick reference card. The second time I picked up the radio, I was able to figure out how to delete the two pre-programmed channels and how to get it to scan the programmed memories.

In addition to ordering the radio, I also purchased the programming cable, but it’s on back order. After programming several of the local repeaters into the HT, and seeing how easy it is to do, I’m considering canceling that order. I’m not a big VHF/UHF user, and I don’t continually update the programming of my radios, so I’m not really sure that I need that programming cable.

So, how does it work? Well, to be honest, I’ve only been able to make one contact with it so far, and that was a really short one because the other guy was driving away from the repeater and quickly was out of range. I don’t fault the radio for this, though. Like many places, the repeaters are around here are dead. I had the radio turned on all day Wednesday and only heard a couple of “kerchunks.” I don’t recall hearing an entire conversation.

I don’t really have the equipment to properly test the performance of the radio, but I will say that the receiver doesn’t seem to be as sensitive as the other HTs that I own. That’s not a big problem, though, as they’re still solid copy.

All things considered, it seems to be a decent purchase. It would be nice if there were more people to talk to, though.

Filed Under: Gear/Gadgets, VHF/FM/Repeaters

Ads of Note from the December 2012 QST

November 18, 2012 by 3 Comments

When I was a kid, I used to religiously pore over the ads in the Electronics Illustrated, Popular Electronics, and later on, QST issues that I received. I don’t do that every month nowadays, but I think it is a worthwhile exercise to do every two-three months. New products are always being introduced, and some of them can be quite useful and fun.

This month, I went through the ads in QST. Here are some that I highlighted.

  • Using Your Meter. This is a new book from The W5YI Group. It’s notable to me because I’ve been thinking that a simliar book might be my next publication. The No-Nonsense Guide to Using Your DMM—my working title—would be a lot cheaper than the $24.95 that W5YI is asking for this book, though.

    Got any tips for using a DMM? If so, e-mail me and I’ll include it in the book.

  • Bonito RadioJet 1102S. This is a software-defined receiver made in Germany and imported by a small company, Computer International, in Michigan. Unfortunately, the company’s website is a real disaster. I spent about ten minutes looking for a price for this radio without any luck.  So many small companies’ websites are so poor that I think it actually hurts, rather than helps their business.
  • MastrAnt. This company sells synthetic guy ropes. We’re going to need some of this down at the museum. I think the metal guy wires are detuning our 40m inverted Vee.

Do you peruse the ads in QST and other ham radio magazines? Which ones have you found interesting lately?

Filed Under: antennas, Books and Magazines, Software-Defined Radio (SDR)

On the Internet: $100 supercomputer, 13 yo reviews his HT, HackRF covers 100 MHz – 6 GHz

October 25, 2012 by Leave a Comment

Here are  a couple more interesting tidbits gleaned from the Internet over the past week or so:

  • Personal supercomputer for only $100! This blog post describes reports on a company called Adapteva, which sounds like it’s still basically a basement operation, that’s developed a low-power, high-Gflops processor chip. Their current project is to develop a very low-cost supercomputer using this chip. One of the possible applications they’re targeting is software-defined radio.
  • 13-year-old reviews the Quansheng dual-band HT. A new ham reviews his dual-band HT. Bottom line: he likes it!
  • HackSDR to rule the airwaves. HackRF is a software-defined radio (SDR) that will potentially receive and transmit any radio frequency from 100 MHz to 6 GHz. HackRF is intended to hit the sweet spot between versatility and cost – around the size of a USB hard drive and with a $300 price tag,
Filed Under: Gear/Gadgets, Software-Defined Radio (SDR), VHF/FM/Repeaters

25, 50, and 75 Years Ago in QST

October 14, 2012 by 2 Comments

QST publishes a column every month towards the back of the magazine that highlights from issues 25, 50, and 75 years ago. Now that the QST archive is online, it’s really worth taking a look at these articles. Here are a few that were interesting to me this month:

  • October 1937
    • Modernizing the Simple Regenerative Receiver by Vernon Chambers, W1JEQ. This a nicely-designed and built regen using two tubes, a 6K5 pentode and 6C5 triode. I’m going to keep this design in mind if I ever get around to playing with all the tubes I have. As an aside, W1JEQ wrote 87 articles for QST from 1936 through February 1958. This was his third article.
    • Concentrated Directional Antennas for Transmission and Reception by John L. Reinartz, W1QP, and Burton T. Simpson, W8CPC. This article describes two different antennas. The first is a  half-wave loop antenna that the author says works on 2-1/2, 5, 10, and 20m. The second is a square loop antenna called a “signal squirter” for 14 Mc.
  • October 1962
    • In the “New Apparatus” item on page 27, a key made by J. A. Hills, W8FYO, of Dayton, OH is shown under the heading, “New Key Mechanism for Electronic Keyers.” The photo clearly shows a key whose design was adopted by whoever designed the Bencher BY-1 paddle.
    • The Towering Problem by Jay Kay Klein, WA2LII clearly shows that putting up towers have always been a problem for amateur radio operators. This is a humorous take on the problem. What’s notable is that this type of humorous article almost never appears in QST anymore. Amateur radio seems to have lost its sense of humor.
  • October 1987
    • Stalking Those Fugitive Components by Doug DeMaw, W1FB. We often complain about the demise of local parts suppliers, but this article shows that this was a problem 25 years ago as well. W1FB gives some advice that I gave not long ago–stock up on parts, especially when you find a good deal on them, and you won’t have to scrounge around for them when you want them.
Filed Under: antennas, Building/Homebrew, CW, Receivers

From the trade magazines – 092612

September 26, 2012 by Leave a Comment

Three more articles from recent editions of the electronics trade magazines.

HeathkitHeathkit: A right-time, right-place business. Heathkit was a popular electronics company for decades before its demise earlier this year. Former employees Lou Frenzel and Chas Gilmore share some memories and discuss the factors that led to its closing. Lou Frenzel is W5LEF.

In the article, he notes how he was instrumental in developing the Heath/Zenith line of computer kits. At that time, I was a fledgling test engineer working for Memorex (remember them?) making the 8-in. floppy drives that were an option for those computers.

Real-world testing of wi-fi hotspots. This article talks about both the RF testing and data communications testing needed to ensure a good wi-fi hotspot.

How to simulate cable in SPICE. This article covers the two main loss effects related to cables (the skin effect and dielectric losses) and presents a simple cable modeling method for use in standard SPICE simulators.

Filed Under: Circuit Simulation, Digital Communications, Everything Else, Kits

Extra Class question of the day: Frequency counters and markers

September 20, 2012 by 2 Comments

To measure the frequency of a signal, you use an instrument called a frequency counter. The purpose of a frequency counter is to provide a digital representation of the frequency of a signal.(E7F09) A frequency counter counts the number of input pulses occurring within a specific period of time. (E7F08)

To accurately measure high-frequency signals digitally, you need a highly stable and accurate frequency source, called the time base. The time base provides an accurate and repeatable time period, over which you count the number of pulses of the test signal. The accuracy of the time base determines the accuracy of a frequency counter. (E7F07)

An alternate method of determining frequency, other than by directly counting input pulses, that is used by some counters is period measurement plus mathematical computation. (E7F10) An advantage of a period-measuring frequency counter over a direct-count type is that it provides improved resolution of low-frequency signals within a comparable time period. (E7F11)

You also need an accurate and stable time base to generate and receive microwave signals. All of these choices are correct when talking about techniques for providing high stability oscillators needed for microwave transmission and reception: (E7F05)

  • Use a GPS signal reference
  • Use a rubidium stabilized reference oscillator
  • Use a temperature-controlled high Q dielectric resonator

If you want to measure a signal whose frequency is higher than the maximum frequency of your counter, you might use a prescaler. The purpose of a prescaler circuit is to divide a higher frequency signal so a low-frequency counter can display the input frequency. (E7F01) A prescaler would, for example, be used to reduce a signal’s frequency by a factor of ten. (E7F02)

You might use a decade counter digital IC in a prescaler circuit. The function of a decade counter digital IC is to produce one output pulse for every ten input pulses. (E7F03)

In some cases, you might use a flip-flop. Two flip-flops must be added to a 100-kHz crystal-controlled marker generator so as to provide markers at 50 and 25 kHz. (E7F04) The purpose of a marker generator is to provide a means of calibrating a receiver’s frequency settings. (E7F06) You mostly find marker generators in older, analog receivers.

Filed Under: Digital Logic, Extra Class Question of the Day, Test Equipment

Extra Class question of the day: Modulation and demodulation

September 12, 2012 by Leave a Comment

Modulation is the process of adding some kind of information, including voice and digital information, to a carrier signal. The most common types of modulation that we use in amateur radio are amplitude modulation (AM) and frequency modulation (FM). Single-sideband, or SSB, is a form of amplitude modulation.

To frequency modulate a carrier, a transmitter will sometimes us a modulator that varies the phase of the signal. This is sometimes called phase modulation (PM). One way to generate FM phone emissions is to use a reactance modulator on the oscillator. (E7E01) The function of a reactance modulator is to produce PM signals by using an electrically variable inductance or capacitance. (E7E02) An analog phase modulator functions by varying the tuning of an amplifier tank circuit to produce PM signals. (E7E03)

To boost the higher audio frequencies, a pre-emphasis network is often added to an FM transmitter. (E7E05) For compatibility with transmitters using phase modulation, de-emphasis is commonly used in FM communications receivers. (E7E06)

Amplitude modulation and single-sideband signals are produced using mixer circuits. The carrier frequency and the baseband signals are input to the mixer circuit which produces an amplitude modulated output. The term baseband in radio communications refers to the frequency components present in the modulating signal. (E7E07) The principal frequencies that appear at the output of a mixer circuit are the two input frequencies along with their sum and difference frequencies. (E7E08)

When using a mixer, you must take care not to use too high of a signal at the inputs. Spurious mixer products are generated when an excessive amount of signal energy reaches a mixer circuit. (E7E09)

Single sideband is most often used for phone transmission on the HF bands and for weak-signal operation on the VHF and UHF bands. One way a single-sideband phone signal can be generated is by using a balanced modulator followed by a filter.  (E7E04) A balanced modulator is a type of mixer.  The output of a balanced modulator, however, does not contain the carrier frequency, only the two sidebands.

Modern transceivers use digital signal processing to generate SSB signals. The quadrature method describes a common means of generating an SSB signal when using digital signal processing. (E7E13)

At the receiving station, a modulated signal has to be demodulated. Amplitude modulated signals are often demodulated using a diode detector circuit. A diode detector functions by rectification and filtering of RF signals. (E7E10)

For demodulating SSB signals, you want something a little more sophisticated. A product detector is a type of detector that is well suited for demodulating SSB signals. (E7E11) A product detector is actually a frequency mixer. It takes the product of the modulated signal and a local oscillator, hence the name. In an FM receiver, the circuit for detecting FM signals is a frequency discriminator. (E7E12)

Some modern receivers demodulate a signal entirely in software. These receivers are called software-defined receivers. When referring to a software defined receiver, direct conversion means incoming RF is mixed to “baseband” for analog-to-digital conversion and subsequent processing. (E7E14)

Filed Under: Circuit Design, Extra Class Question of the Day, Receivers, Transmitters

Extra Class question of the day: Receiver performance characteristics

September 9, 2012 by Leave a Comment

One of the most commonly mentioned HF receiver specifications is blocking dynamic range. The blocking dynamic range of a receiver is the difference in dB between the noise floor and the level of an incoming signal which will cause 1 dB of gain compression. (E4D01) Cross-modulation of the desired signal and desensitization from strong adjacent signals are two problems caused by poor dynamic range in a communications receiver. (E4D02)

Another specification commonly bandied about is third-order intercept level. A third-order intercept level of 40 dBm with respect to receiver performance means a pair of 40 dBm signals will theoretically generate a third-order intermodulation product with the same level as the input signals. (E4D10) Compared to other products, third-order intermodulation products created within a receiver are of particular interest because the third-order product of two signals which are in the band of interest is also likely to be within the band. (E4D11)

The term for the reduction in receiver sensitivity caused by a strong signal near the received frequency is desensitization. (E4D12) Strong adjacent-channel signals can cause receiver desensitization. (E4D13) One way to reduce the likelihood of receiver desensitization is to decrease the RF bandwidth of the receiver. (E4D14)

A preselector might help in some cases. The purpose of the preselector in a communications receiver is to increase rejection of unwanted signals. (E4D09)

When operating a repeater, one thing that can occur is intermodulation interference, or simply intermod. Intermodulation interference is the term for unwanted signals generated by the mixing of two or more signals. (E4D06) Nonlinear circuits or devices cause intermodulation in an electronic circuit. (E4D08)

Intermodulation interference between two repeaters occurs when the repeaters are in close proximity and the signals mix in the final amplifier of one or both transmitters. (E4D03) The transmitter frequencies would cause an intermodulation-product signal in a receiver tuned to 146.70 MHz when a nearby station transmits on 146.52 MHz are 146.34 MHz and 146.61 MHz. (E4D05) We get this in the following way:

2 x 146.52 MHz – 146.34 MHz = 146.70 MHz and

2 x 146.61 MHz – 146.52 MHz = 146.70 MHz

A properly terminated circulator at the output of the transmitter may reduce or eliminate intermodulation interference in a repeater caused by another transmitter operating in close proximity. (E4D04) The circulator reduces intermodulation distortion because it helps to reduce the amount of energy from nearby transmitters that might get into a repeater’s final amplifier.

Cross modulation is a form of intermodulation. Cross modulation occurs when a very strong signal combines with a weaker signal and actually modulates the weaker signal. The most significant effect of an off-frequency signal when it is causing cross-modulation interference to a desired signal is that the off-frequency unwanted signal is heard in addition to the desired signal. (E4D07)

Filed Under: Extra Class Question of the Day, Receivers
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