From the Trade Mags

I’m on the distribution list for many different electronics trade magazines. Quite often, there are articles of interest to amateur radio operators. Here are four of them—two from electronic design and two from EE Times—that I hope you’ll find interesting.

Radiated efficiency: A true measure of antenna performance
Many engineers tend to think of antennas in terms of gain, but the author argues that we’d be better off if instead we evaluated antennas in terms of efficiency, that is how well it turns the power supplied to the feedpoint into radiated energy.

And You Thought The 555 Timer Was Dead?
Recently, both Advanced Linear Devices and Semtech have redesigned the 555 timer chip, improving it in many ways and extending its usefulness—most likely—for years to come.

Melville Eastham: Workplace Innovator Crafts Early Electronic Products
Eastham was the founder of General Radio. The article points out that Eastham founded the company in 1915 to “serve the rapidly growing ham radio market.” By the late 1920s, that “boom” had subsided, and the company turned its attention to precision measurement instruments. It was very successful doing this for many, many years.

10 Technologies to Watch in 2011
This article predicts that “wireless connects for health care” will be one of the technologies to watch in 2011. Makers of medical electronics equipment, apparently, are planning to integrate their gear using Bluetooth.

You Get What You Pay For

At the Maker Faire on Saturday, I pulled out my $2 Harbor Freight DMM to check the continuity of the light bulb in my “visualize RF” demo. Bad news. The “low battery” indicator was on, and apparently it couldn’t supply enough current to make the measurement. On top of that, as I was fooling around with it, the wire came off one of the probes.

Well, yesterday, I tried to fix things. I re-soldered the probe wire and replaced the 9 V battery, but the meter’s still non-functional. The display comes on, but I’m not able to make any measurements.

I guess the moral of the story is that you get what you pay for. I now have another cheap $2 Harbor Freight DMM in my tool chest. We’ll see how long this one lasts.

Fall Frequency Measuring Test This Week

The W1AW Frequency Measuring Test (FMT) has taken several different formats over the past few years. This year, the ARRL returns to the “classic” FMT — measuring the frequency of an unmodulated carrier. Accurate frequency measurement is required of all hams for both regulatory compliance — “stay in the band!” — and operating convenience, particularly on the new digital modes. The W1AW FMT will run on November 12, 2009 at 0245 UTC (this is Wednesday evening, November 11, 2009 at 9:45 PM EST). It will replace any W1AW bulletin normally scheduled for that time. It is recommended that participants listen to W1AW’s transmissions prior to the event to get an idea of conditions to see which band (or bands) will be best for measurement purposes. Read more here.

Don’t Be a Dummy and Spend Too Much for Oil

Tim, N9PUZ writes to the HamRadioHelpGroup mailing list:

With new HF rigs being 100% solid state these days, the need for a dummy load in some shacks has gone away. However, if you have an amplifier they are very useful as you can do most of your tuning off-air and avoid causing QRM.

Recently, I bought a used Heathkit Cantenna. It is a dummy load similar to the MFJ-250 1kW “wet” dummy load. It did not come filled with oil due to shipping difficulties.

In many places, such as where I live, genuine transformer oil to fill the load is unobtainium. You can buy a gallon from MFJ but it costs $30 plus shipping.

According to the Heathkit documentation, a good substitute is mineral oil. I checked at the local pharmacy and they wanted $4.25 per PINT still making this an expensive proposition. I wouldn’t classify myself as cheap but I am frugal so I kept searching.

An Internet search led to my discovery that mineral oil is often used as a laxative for horses and other farm animals. A quick trip to our local farm store “Farm and Home” got me a gallon jug for just $15. I imagine any store of this type or even the local Vet would have some.

The amplifier tunes up into the Cantenna very nicely now. Life is good.

Tim, N9PUZ

This is a great tip, but I disagree that “the need for a dummy load in some shacks has gone away.” Every shack should have a dummy load. They are immensely useful, especially in situations where you’re not whether your antenna or your transmitter is what’s causing you not to transmit properly.

Cheap Sig Gen Kits

On the qrp-l.org mailing list, someone asked about signal generator/function generator kits. Ken, N9VV, came up with the following list:

As always, there was a lot of back and forth on the topic. One guy noted that none of these were really “good” function generators. My comment was that for such low prices, they might be fun to play with.

A third commented that by looking around at hamfests one could probably purchase something much better for just a little more. He’s right about that. A couple of years ago, I scored a 2 MHz B+K generator for about $120. It even does amplitude modulation.

Of course, another approach is to use your PC’s sound card as a signal generator. This works fine if all you need is audio signals. You could even get fancy and do modulation or other types of arbitrary waveforms. Two software packages that will allow you to do this are Marchand Function Generator Lite (free) and NCH Tone Generator ($20).

Finally, someone suggested using an iPod for audio test waveforms. Using a computer’s sound card, you can generate all kinds of test waveforms, record them on the iPod, then just select the tracks you want when you want them. That’s a neat idea. Someone should prerecord a bunch of commonly used waveforms and make them available on a website somewhere.

How to use an oscilloscope

updated 3/15/12

On the Elecraft mailling list, there was a request for help finding an oscilloscope tutorial. Since this is right up my alley–I’ve written for Test&Measurement World magazine for a zillion years–I thought I’d do a little research.

A Google search turned up a bunch of online tutorials. When I first posted this in 2004, one of the tutorials that I liked was http://www.oscilloscope-tutorials.com. Unfortunately that website is no longer online. Instead, go to YouTube, and have a look at How to use an oscilloscope, a video produced by two young Tektronix engineers that explains the basics of a scope’s vertical and horizontal controls and triggering.

Another tutorial that I liked is an article from the American QRP Club website. Written by Paul Harden, NA5N, this long article explains not only how scopes work, but also how to check and calibrate a scope that you may have purchased at a hamfest. Very useful info.