Monthly Archives: February 2010

New DRM channel of Disco Music

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.

via New DRM channel of Disco Music  :: DRM.

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.

The Disco Palace broadcast using Digital Radio Mondiale on 17.755Mhz

Low Voltage Vacuum Tubes

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.

Low Voltage Tubes

Tubes? Who uses tubes anymore?

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:


httpv://www.youtube.com/watch?v=PYeB7nGwGv0

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.

Addendum: Here’s another link for inspiration.

K6FIB again…

This morning, I see K6FIB back, this time in all caps as he said he would be, along with perennials KC7VHS and WA5DJJ. Good clean signal.

Still no trace of him on WA0UWH’s grabber, but KK7CC has no trouble getting him:

New Book: International QRP Collection

While over at Ham Radio Outlet the other day, I noticed a new QRP/homebrewing book on the shelf published by the RSGB:

International QRP Collection, edited by Rev. George Dobbs and Steve Telenius-Lowe.

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.

Fifth Position, a test for milhouse

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

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.

      +1 : [-5] 0.00s
         : 27-24
      +3 : [3] 0.00s
         : 27-24 11-15 20-16
... researching after failing low (-122)
      +5 : [-124] 0.00s
         : 27-24 11-15 20-16 14-18 21-17
... researching after failing high (-9)
      +7 : [-9] 0.00s
         : 20-16 11x20 27-23 12-16 19x12 20-24 12-8
... researching after failing low (-34)
      +9 : [-37] 0.00s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  27-32 23-18
     +11 : [-35] 0.01s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  27-32 23-18
         : 10-14 18-15
     +13 : [-40] 0.02s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  10-14 19-15
         : 27-32 23-19 32-27 15-10
... researching after failing low (-78)
     +15 : [-116] 0.08s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  10-14 19-15
         : 12-16  9-6  27-32  6-1  32-27 23-18
     +17 : [-119] 0.23s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  10-14  9-6
         : 27-32 19-15 12-16 23-18 14x23  6-1  32-27  1-5
     +19 : [-114] 0.72s
         : 27-23 11-15 20-16 15x24 16-11 10-15 23-19 14-18 19x10
         : 18x25 11-8  24-27 10-6  27-32  6-1  25-30
... researching after failing high (-89)
     +21 : [-11] 2.65s
         : 20-16 11x20 27-23 20-24 22-18 13-17 18x9  10-14  9-6
         : 24-27  6-1  27-31  1-5  31-27  5-9  27x18 19-15 18x11
         : 9x18
     +23 : [-16] 5.54s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  27-32 23-18
         : 10-14 18-15 13-17  9-6  17-22  6-1  22-26 15-10
     +25 : [-17] 13.83s
         : 20-16 11x20 27-23 20-24 22-18 24-27 18x9  27-32 23-18
         : 10-14 18-15 13-17  9-6  32-27  6-1  17-22 15-10

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.

Build Your 1st Vacuum Tube Regenerative Receiver

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.

Lindsay: Build Your 1st Vacuum Tube Regenerative Receiver

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.

We’ll see how far this project goes.

Some new additions to my checkers library…

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...

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 <em>American Draught Player</em>

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.

The Carolina Flashers Photonics Group

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:

The Carolina Flashers Photonics Group – Welcome.

Addendum: They link to a fascinating demonstration of a German WW2 light-based transceiver system. Very cool.


httpv://www.youtube.com/watch?v=vR4N6MTx_vw

Rob Pike on Quantum Computing

Rob Pike is a Google researcher, and has written a bunch of stuff in the past that I’ve enjoyed reading.  He’s also a telescope maker, which scores big points with me.   I recently discovered that he also write an introduction to quantum computing that I had not previously read.   This is an area of computer research that I quite franly know othing about, so I’m bookmarking it for my later consmption.

XBM80-2 An Experimental 80m CW Transceiver G3XBM

I’ve been a little too busy to fire up the soldering iron and build anything, but I’ve been pondering putting together one of Roger’s G3XBM radios. I ordered a couple of high impedance crystal earphones just to be ready, but in the mean time, I’m studying the circuit diagrams fairly closely:

XBM80-2 An Experimental 80m CW Transceiver G3XBM.

80_2revEexport

The radio is simple enough that I should be able to understand it completely, but I must admit that I don’t understand the principle of regeneration very well, so staring at radio, it’s not particularly obvious to me how T1 serves as both mixer and oscillator. I also am not certain I see how the oscillator doesn’t radiate when the radio is in receive mode. I’ll ponder it some more, and maybe fire up LTSpice over the weekend to test my understanding.

Gruenberger’s prime path

Here’s an interesting little mathematical morsel from the pages of the bit-player blog having to do with two topics I’ve found interesting in the past: prime numbers and random walks.

Let’s consider the sequence of prime numbers > 3. All such primes are congruent to -1 or to 1 modulo 6. So, let’s use that as the “random” variable controlling a random walk. If you consider all odd integers, you can generate a walk as follows. Take a step in the current direction. If the number is composite, you are finished. Otherwise it is a prime. If it is congruent to -1 modulo six, then turn left, otherwise turn right. You end up with a “random” walk, with several interesting questions about whether it shares properties with real “random” walks. Check the blog entry for more discussion:

bit-player » Gruenberger’s prime path.

I can visualize an interesting program written to draw these which is a modification to the segmented sieve algorithm that I’ve coded up previously. Each “segment” generates a segment of the overall path, and as long as you know the coordinates of the starting position, you can overlay and merge these points with reasonable efficiency. I might have to give that a go some time.

Addendum: In searching for more material by Gruenberger, I discovered that he was an early proponent of the educational uses of computing, and that some of his papers are available for download from the RAND corporation.

Real-Time Rendering Blog

Back around 1984 or so, I first became interested in computer graphics. I was going to college at the University of Oregon, and we didn’t really have any graphics courses or any computers that you would think would be good at displaying graphics. Eventually they got a Tektronix 4115 terminal (which was huge, and cost about $20K in the day if memory serves), which I got hooked to our VAX 11/750, and I had my platform. I started to read and experiment with raytracing. Some early enthusiasm and guidance was provided over USENET by Eric Haines, who I must thank for helping inspire and inform me in those early years. Eric’s patience has shifted from being measured in Blinns to milli-Blinns now, and he’s authored a book called “Real-Time Rendering” and also maintains a very useful blog on the subject. Every once in a while, I glance over and realize that the world is changing, and I’m not keeping up. But if you want to keep up with developments, Eric’s blog will be a good place to start.

Real-Time Rendering · Tracking the latest developments in interactive rendering techniques.