The Amateur Amateur: Putting It All Together (A Kitbuilding Saga)

By Gary Hoffman, KB0H
Contributing Editor
April 21, 2002

Kit-building frustration is at the core of this month's adventure. A kit that I'd hoped would nurture my wife's fledgling interest in the mechanics of radio turned out to have just the opposite effect.

Did you have an Erector Set when you were young? Perhaps you had a box of Tinker Toys or Lincoln Logs. You may have moved on to building models when you got older. Regardless of your sex, you probably had some toy or toys that required that you put something together. When you put these toys together, you undoubtedly learned something about how they worked.

That is the idea behind kits. You put the kit together and learn something about how the finished product works. At least, that's the theory.

Nancy, my wife, is actually the kit builder at our house. She feels that she can learn more about radios when she can actually put one together. This was one of her goals when she first got into Amateur Radio--to learn how a radio works.

Not long after we got our tickets, I bought Nancy three kits. I figured the first kit would be easy, the second a bit more challenging and the third somewhat difficult. Of course, I was subconsciously thinking how difficult they would be for me. Now, I didn't really get into electronics until I got my amateur license, but my father ran a radio and television shop for many years, so I had some exposure to it. Nancy, on the other hand, was unfamiliar with the tools and the terminology. Her only exposure to the fundamentals of electronics and radio was when she studied for her ham license.

The kits were somewhat daunting, but she is a very determined person. I gave her a tour of the workbench and a crash course in soldering. She opened kit number one and started reading the instructions.

I must say that Nancy had far fewer problems with the kit than I had expected. She did ask me a few questions, and my answers tended to be along the lines of, "Well, it's pretty obvious that . . . hmmmm! I guess it's not all that obvious after all." If you've never handled a diode, for example, it's not obvious which end is which (I'm still not sure). The diagram that came with the kit showed where to place the components on the board and marked which end was positive. The actual components, however, were only marked at the negative end. Well, sure. Intuition told us that the unmarked end of the component was positive (likewise the unmarked end on the diagram was negative), but why the heck weren't the diagram and components marked the same way? I mean, give us a break!

We were new at this and still full of insecurities. Instead of reassuring us, the kit was making us doubt each decision.

diagram showing component value ranges

Once you fudge the fudge factor, you end up way outside the margin of error.

Nancy finished her kit in a few days. It did not work. It was supposed to pick up shortwave broadcasts. All we got by tuning across the band was a lot of silence interspersed with an occasional Snap! Spit! Blaaatt! That was enough for Nancy. She tossed the radio on the workbench and left in frustration.

Not wanting to see her first kit-building experience end on such a sour note, I decided to check over her work. I spent about half an hour looking at the radio and determined that Nancy had put the kit together correctly. So why were we picking up Snap! Spit! Blaaatt! instead of the BBC?

Well, this bugged me. The kit that I'd hoped would nurture Nancy's fledgling interest in the mechanics of radio instead had the opposite effect. I just had to know why the radio didn't work (picking up Snap! Spit! Blaaatt! didn't count).

I underwent a transformation. Exit Gary, mild mannered programmer and husband, and enter Compulsive Man! Lock the doors. Hide the children. The Insane Avenger is here.

I read the kit's instruction manual carefully. I didn't miss a single comma, period, or hyphen. I compared each component with the parts list. I examined each component and its placement on the circuit board. I checked every solder joint. I squinted at everything through a magnifying glass. I used a meter to check every part of the circuit. And eventually, using my Amazing Compuls-o-Vision, I found out what was wrong. The kit's manufacturer had supplied the cheapest, most inferior components available.

SR1 kit

No BBC, just Snap! Spit! Blaaatt!

Here is what happened. Electronic components (resistors, capacitors, diodes and so forth) are marked with the appropriate value. For example, a resistor may tell you (in color code-ese, of course) "Hi there. I am a 100-ohm resistor."

But wait! There is often another little color band (or no band at all) on the component that indicates the tolerance, which might be 1, 5, 10, or even 20 percent. Good components will have a low tolerance. So, let us assume that our sample resistor was marked to show that it had a 10% tolerance. Its translated color code would tell you, "Hi there. I am a 100-ohm resistor. But my tolerance is 10%, so I might be a 90-ohm resistor, or I might be a 110-ohm resistor, or anything in between. Ha-ha!"

Okay, store this away while I move on to the next part of the explanation.

The kit's instructions explained where to put each component ("Place a 250-ohm resistor here"). Even better, the instructions gave the range of component value that could be used in a particular spot. That is, for a particular place in the circuit, you didn't have to use a 250-ohm resistor. You could use anything from a 240 to a 260-ohm resistor, and the radio should still work. Nice, eh?

Right. Now, here is why the radio didn't work. First, many of the supplied components had values that were not in the middle of the range of values that could be used. They were on the edge of the values that could be used. Second, virtually every component had an immensely wide tolerance. So most of the components may have had values well outside the useful range. For example, the instructions called for 100-ohm resistor but said anything from 90 to 110 ohms would suffice. The kit supplied a 110-ohm resistor, however--right on the edge of the useful tolerance range.

Kit components

What are the real values of these components?

Worse than that, it had a 15% tolerance, which meant it might have a value as high as 126.5 ohms, well outside of the useful range. No wonder the blasted radio didn't work!

I went to an electronics store and bought new components, all with much tighter tolerances. I removed the kit-supplied components, put in the new components, and sure enough, the radio started receiving shortwave signals.

Let me reiterate the purpose of kits. They are supposed to help you learn. Nancy wanted to learn how radios work. What she learned instead was why some radios don't work. Well, it was a lesson, but hardly a satisfying one.

What I learned is never to buy another kit from that particular manufacturer.

Editor's note: ARRL member Gary Hoffman, KB0H, lives in Florissant, Missouri. He's been a ham since 1995. Hoffman says his column's name-- "The Amateur Amateur"--suggests the explorations of a rank amateur, not those of an experienced or knowledgeable ham. His wife, Nancy, is N0NJ. Hoffman has a ham-related Web page. Readers are invited to contact the author via email.

© 2002 American Radio Relay League


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