brainwagon "There is much pleasure in useless knowledge." — Bertrand Russell

9Jan/124

Seeing double on QRSS grabber…

Here is a snapshot from my QRSS grabber earlier today. You might want to click it to see it full size:

I'm curious: what phenomenon is causing the strong line doubling of the signals near the bottom? Note: not all the signals demonstrate this phenomenon, and it's relatively rare, and commonly just fades away. Also note that the signal at the top does not show this line doubling. I suspect all the signals which are line doubled are in New Mexico.

Bonus question: I keep seeing a small wiggle like the one around 10.139975 or so, starting on 10 minute boundaries and lasting for about one minute. Anybody have any idea who that is?

Filed under: Amateur Radio, QRSS 4 Comments
9Jan/121

On junkboxes…

I've recently begun to try to systematically (if somewhat erratically) equip my home office (it aspires to be a lab) with the necessary parts and tools that I need to assemble projects which interest me. The reason for this is simple: if you have the tools, material and space to do a project, you will much more likely do it than if you have to acquire all three specifically. If, for instance, you want to experiment with RF oscillators or amplifiers, if you have toroids, transistors, crystals, caps and resistors floating around, you can tack one together in just a few minutes. If you toss in some diodes, you can make some mixers. Maybe you want to have some ICs around, such as the LM386s. Toss in some speakers, jacks and the like, and voila: you are building radios.

When you are just starting, each additional part or tool that you "need" but don't have is stumbling block: it halts your progress, and keeps you from the projects that you truly want to do. So, how do you get from where you are (presumably with nothing) and get to the point where you can build things than interest you?

Here are some simple, and somewhat obvious guidelines.

  • Take a long view. You might know someone who's garage is stuffed full of cool stuff, and what you envision as highly complex and detailed projects just seem to flow effortlessly off his desk. As far as I know, nobody starts with such collections as they emerge from the womb, so at some point, they were where you are today. Don't suffer any angst over your relative lack of equipment and expertise. Peter Norvig has an excellent essay on learning to program. People have the expectation (fueled by books with titles like Learn to Program in 21 Days) that programming is easy, and they should be able to become experts quickly. But research shows that it takes years to develop expertise. This is good: it means you can invest modestly in acquiring the tools and materials you need, gathering both simultaneously over time.
  • Invest in tools first, consumables second. Since we are taking a long view, it makes sense to invest in tools. After all, if it takes you ten years to acquire skills, chances are you are going to use those tools quite a bit. On the other hand, components and consumables will probably get used up in projects. Acquire them lazily, as you need them, or as you find them.
  • Consider economies of scale. Often ordering a dozen of a particular part is the same cost as just ordering two or three. As an extreme example: consider the lowly 2N3904 NPN transistor. If you buy these one at a time at Radio Shack, you'll pay about $1.19 for one. Digikey will sell them for something like $.43 in quantity one, but are down to $.12 if you buy one hundred of them. If you go to companies like Tayda Electronics you can get them for just $0.01 a piece. Consider adding fairly bulk quantities of common components to stock your junk box.
  • Substitute for hard to find components. Most of the rehashed circuits that the ham radio magazines continue to republish seem to need air spaced variable capacitors, which are frankly getting harder and harder to get, and more expensive when you can. Keep an eye out for those components, but also consider making substitutions. Hans Summers made me aware of using LEDs and other diodes as varactors. Varactors are reasonably difficult to find, but LEDs are everywhere. If you dig around, you can find articles like this excellent one on how to design circuits around this idea.
  • Spend time researching and asking questions. It's easy to spend money, it's hard to save money. But if you spend some time doing research, you can often learn a lot, and therefore save a lot. DIg around. See what others have done. View everything through the lens of what skills and equipment you'd need to reproduce the same kind of projects that you see.

That's the general background: in the next few days I'll try to do a post of what items are making it into my junkbox. Stay tuned.

Filed under: Amateur Radio 1 Comment