Focusing guides for telescopes

Today I was cleaning out my office. I’m a clutterbug: I have tons of treasures, but also, let’s face it, an even larger amount of crap. When I first moved to California 19 years ago, everything I owned fit in 13 banker’s boxes. Now, I don’t even think my power adapters would fit in 19 bankers boxes. So, I was ruthlessly going through boxes and tossing stuff out. Along with endless old cds, and papers that I printed out, I found a bunch of stuff from one of my previous obsessions: telescope making. I even found a 6″ mirror, aluminized, carefully wrapped in optical tissue. I’ve pretty much abandoned telescopes in recent years, but I really should get back into it again.

Anyway, tonight I was strolling down memory lane, and encountered a link to something I hadn’t seen before: the Bahtinov Mask. It’s a gadget that you can place in front of a telescope to help you focus precisely. It uses a very clever arrangement of masks to produce a diffraction pattern which can be adjusted to a precise focus.

If you dig around, you can find all sorts of testimonials about how terrific they are. I’ll have to make one of these and give it a try. Perhaps if I can find someone who will loan me a laser cutter, I’ll even cut a really precise one.

Addendum: Here’s a link to a nice mask generating program that will output an SVG file for any scope you need.

Where are the visionaries in ham radio?

I was reading amateur radio blogs and for the third time or so in a month, I was treated to what amounted to a diatribe against software defined radio. When I read these, I can’t help but sigh in frustration.

I understand nostalgia. We all like the cars we wish we could have had when we were teenagers. We like the music that we learned to like as young people. Heck, I still have the first computer that I bought at age 14. In moderation, nostalgia can be a good thing. It reminds us where we came from. It gives us context. It gives us history.

But I think we always have to temper a sense of nostalgia with perspective and vision. Our first cars were our loves, but they were (let’s face it) often gas guzzling, unreliable death traps. Some of our music was probably brilliant, but a lot of it was (let’s face it) crap. And my first computer, while enabling me to explore a world of computation, which eventually led a rich and rewarding career, was by any modern standards less powerful than an alarm clock.

Which brings me to software-defined radio.

I’ve seen lots of people write negatively about software defined radio. Often it’s just pure nostalgia. “Real radios glow.” “Real radios have KNOBS.” “Real radios don’t require your laptop.” “My old radios just sound better.”

I think we as hams should be more visionary than these statements. Software-defined radio is enabled by the remarkable evolution of computing hardware. The speed of computation has in the time that I’ve owned computers increased by a factor of about 200,000. The cycle time of most desktop computers is now low enough that an inexpensive computer can execute dozens of instructions for every cycle of an HF signal. This enables the traditional features of radios like mixing and filtering to be done in software, instead of being cast in hardware. This means that we can have unprecedented control over these processes. And, potentially we can even change many aspects of operation even after the soldering of our radio is complete. Software isn’t a panacea, but it is the source of such great power it can’t and should not be ignored.

Most of the criticisms I see about radio interface seem curiously misplaced. I agree that using your laptop as an interface is often sub-optimal. But if you’ve played with any radios at all, I bet you had some criticism about the conventional radios that you had as well. Modern radios are complex, and this complexity is not often controlled by careful user interface design, whether in software or in conventional hardware front panels. Even if you thought that some radio you had in the past was perfect, I would submit that it would still be beneficial to use software defined radio technology inside.

But even beyond that, I have been playing with an SDR-IQ for the last couple of months. Its ability to monitor all signals on an HF band is enormously compelling. Using digital displays, we can give the user a perspective on the entire band which is undeniably useful. Technology like CW Skimmer can track dozens of Morse signals in real time. Programs like HRD and fldigi can do the same with multiple PSK signals.

I’ve seen a few people abandon the idea of software-defined radio simply because they aren’t adept at software design or have no knowledge of the mathematics and algorithms that underly software-defined radio. They fatalistically claim that they will never or can never understand or learn how software-defined radios work. I am kind of flabbergasted by this attitude. It’s not that it is easy: far from it. Studies show that to become expert in a subject takes the better part of a decade. But as hams, we are supposed to be about self-training and experimentation. Sure, there is no mandate for you to do so, but let’s not be so fatalistic and condemn it merely because it doesn’t coincide with our own abilities or interests.

There is no reason to forget the past, but let’s not worship it either. Let’s look at the best of what was, the best of what we have now, and the best that we can imagine, and experiment, design, build and use the radios that we have yet to invent.

Back transmitting on WSPR…

Well, yesterday I was out shopping at HRO, and couldn’t resist the allure of a new Signalink USB sound interface for my FT-817. This is a sound interface that looks just like a USB sound card when you plug it in, and has rx and tx volume controls on the front.

So, of course, I hauled my FT-817 out of the box it has been in since before the holidays, and had to test it out. The first impressions are a bit mixed. I didn’t have any difficulty at all getting it to work with fldigi or Mixw or Spectran, but for some reason WSPR required a bit of tweaking. It would sometimes just act as if it wasn’t getting any receive audio: the RX level would stay at -30. I suspected that it might have something to do with applications which open the sound card exclusively, so I made sure those were all turned off, and eventually ended up running it in Windows Vista compatibility mode (I have a Windows 7 laptop) and then all was well.

And.. since all was well, I decided to do a bit of WSPR transmitting for the first time in months.

I was heard by VK6DI from his new VK2 location, which was nice to see. David was one of my most distant spots, and his old grabber was the funnest thing for me to check out while testing my QRSS/MEPT beacon stuff before. He’s a few thousand km closer now, but still, Australia is nice. ZL2TLD and I managed to exchange packets. But most interesting was a new station I hadn’t seen before: 4Z4TI. That wasn’t a DXCC prefix which I had seen before in my WSPR spots, so I had to look it up. Yep, Israel. Very nice. Toss in EA4BUL and Japanese stations JA2GRC and friendly face JQ2WDO, and that rounds out my list of DX for the night.