I was looking for some information on how to compute the resonant frequencies that are attainable from small loop antennas, especially for VLF. This appears to be precisely what I’m looking for.
This article describes how to build a loop antenna for low frequency (LF) and medium wave (MW) reception with remote-controlled tuning. The antenna is extremely sensitive and can be built mostly from parts from old radios and tape recorders. Like all loop antennas, it is highly directional, which allows you to null out unwanted noise sources.
AK6L was installing an attic dipole, and idly wondered what the maximum inductance and capacitance the LDG Z11 Pro could swap in. He sent LDG an email, and got a quick response, and since I have the same tuner, I thought I’d write down what they said for future reference. Apparently, it can use 15uH of inductance, and 3000pf of capacitance.
More early reading on vacuum tubes. To be honest, I never really understood (or frankly studied) the physics of semiconductors, which always seemed a bit abstract to me. Having read some of these early texts on how vacuum tubes work, they seem fairly straightforward by comparison. I wonder if I go back and read some introductory semiconductor texts, whether they will seem more straightforward now?
Anyway, another nifty classic text on Google Books:
I believe that it was the Amateur Radio newsline podcast which mentioned the following:
A Miami based Radio Station – The Disco Palace – has started broadcasting a DRM SW channel of ‘best of Disco music’ for listeners in Europe and North America.
So, today I tuned in and recorded some of it using the SDR-IQ, and then processed it with GNU DREAM, the GPL’ed DRM decoder. The signal was very strong, no drop outs, and well, it’s disco. Here’s a couple minutes of the decode.
As part of my delvings into things vacuum tubes, I of course found that many others have been down this road, including this rather interesting receiver built by Alan Yates. Being a novice at this, I was intrigued by the fact that his circuit used the 12DZ6 tube, which could apparently be powered by ordinary 12 volt supplies. Its application was in automobile radio circuits, where high voltages were inconvenient (when needed, they were often generated by “vibrators”, which created an AC voltage from a DC battery voltage, which could then be stepped-up by a transformer). When I mentioned this to Tom, he thought (as I did) that it was odd, and that he didn’t understand how tubes could operate with such low plate voltages. But of course, if you search, you shall find, so I uncovered this terrific page that describes some theory and circuits that use these low voltage (and presumably safer) tubes in radio circuits. Nifty.
For the last week, I’ve been embarking on a ham radio “trip down memory lane”. Well, it would be memory lane if I had any real memories of the tube-based equipment that were staples of the ham shack until probably the 1970’s or so. But if I have a personal philosophy of my little projects, it’s that one has to look back to gain perspective about our current technology. Or something like that. Perhaps that’s just a rationalization for spending time reading old books about vacuum tube design. Or perhaps this is all motivated by the idea of building a radio that glows from scratch. Or, perhaps to demonstrate that I understand the similarities between tubes and FETs.
Whatever the motivation, I’ve been looking around at projects that people have done. A popular project seems to be “twinplex” radio, which uses a single dual triode tube in a regenerative receiver. Staring at circuits and reading Basic Theory and Application of Electron Tubes, I’m beginning to understand the functioning of these circuits. And, it turns out youtube has a lot of nice inspirational videos of people’s projects, such as the following:
Now that the winter is over, our local flea markets at Livermore and De Anza should be starting up again soon. Perhaps I’ll keep an eye out for the components.
It’s not an ideal book from the homebrewer/QRP viewpoint: it includes a bit too much operating/equipment reviews for my taste. Still, it has a number of interesting construction articles, including the “One Transistor Marvel” from Dave Ingram, K4TWJ (SK, sorely missed) which I hadn’t seen elsewhere, but obviously inspired things like G3XBM’s XBM80-2 transciever. It also includes KK7B’s articles on designing and building linear transistor amplifiers that appeared in QST recently. I’d say that’s a waste, but the articles are so good, I’d like to see them in book form (I always seem to lose magazines). It also includes details on some simple minimal rigs that I hadn’t seen before, such as G3MY’s Pippin, and some novel variations on the Pixie.
Overall, I give it an 8/10. Worth having, but not as good as DeMaw’s QRP Design Notebook.
My trip to Powell’s also netted me Erroll A. Smith’s The American Checker Player’s Handbook, a nice little tome published in 1944. It mostly is an introduction to the famous two-move openings, systematically organizing the forty-seven two-move openings into 7 so-called “Master” openings, and then the Major Variations. There are two principle areas that I’d like to see Milhouse, one is the openings, so I think it might be useful once I get going on that project. But in the mean time, it also has some nice positions that are good tests for either its general play, or its play with the endgame database. Witness the so-called Fifth Position:
Fifth Position: White to Play and Draw
Without an endgame database, it takes milhouse a 21 ply search to find the right variation that avoids a loss for white.
The play listed in this line differs a bit after the capture 18×9, but the Cake endgame database lists the move as drawn after that capture, and it appears that milhouse is able to hold a drawing line. Smith lists 27-31 as a drawing variation, but suggests 10-14 as the drawing move. Using the Cake database, it also appears that 12-16 and 27-32 can draw as well.
Using the endgame database, milhouse asserts that the game is drawn with a 7 ply search, after searching less that 1000 nodes, about a 450 fold increase in speed.
In addition to the checkers books that I got the other day, I also picked up a couple of radio books. One was an old book on electric circuits (perhaps the subject of a post some time in the future) and the other was this book from Lindsay books on constructing tube-based regenerative receivers.
It’s a reasonable question as to why you might be interested in trying to build such a thing, but frankly, I don’t have a reasoned answer. I just think it would be cool to experience this technology by actually creating a working example of this kind of art. And it’s kind of cool to build a radio that glows.
One of the chaps that I talk to occasionally on IRC has built an IOio satellite antenna, and was nice enough to post a recording he did with it while tracking AO-51. A nice little recording, and proof that the IOio has plenty of gain for the receive side.
A visit to Powell’s books today netted me three new (well, new to me, but used, and in two cases, quite old) books on checkers. It’s been a while since I mentioned my checkers program milhouse, but it’s still in the back of my mind, and these old books provide excellent insight into the game, and are rich in test cases that can be used to evaluate checkers play. For instance, in Spayth’s American Draught Player, he lists a number of nice positions, like this position, labelled Payne’s #1:
Either side to play, white to win...
Milhouse has no difficulty finding the winning line on simple positions like this, but there are definitely some more subtle positions, and Spayth’s book provides some insight into many common openings. I’ll probably type in some of these problems, and eventually produce a downloadable version of milhouse for all to enjoy.
Addendum: Here’s the most interesting book: a copy of Spayth’s The American Draughts Player, which was written circa 1860. I’m not sure when this edition was printed, but it’s obviously quite old, and yet in pretty good condition.
Spayth's American Draught Player
For those of you who weren’t lucky enough to find a copy of this book, you can nevertheless find it on Google Books:
Addendum2: My copy is a sixth edition, which means that it probably dates to the mid 1890s.
Roger, G3XBM once again turned me on to an interesting link, this one on a group of hams who are experimenting with communication over optical frequencies. This is a topic that has interested me greatly in the past (I seem to be interested in the extremes of amateur radio, both in terms of long wavelengths and short) and seems to be a rich area for experimentation. Check it out:
I'm Mark VandeWettering, husband, proud father of a U.S. Airman, technical director at Pixar Animation Studios, telescope maker, computer science and math afficianado, an Extra class radio amateur licensed as K6HX, and all around geek. I hope you enjoy my website.
I've recently bought a WiFi enabled scale as a motivational tool for my own weight loss. Below, you see the automatic twitter updates from it, along with some notes to myself about my efforts at weight loss. Feel free to follow the twitter user marks_mass and comment and/or encourage.
