G3ZJO just posted a nice little blog entry about the use of LEDs (which are nearly ubiquitous) as varicaps (which are often harder to find). Lots of people are using these in their QRSS beacons, no doubt in part to the work of Hans Summer which was the first person to bring them to my attention. Someday, I’ll begin to work on electronics again, and I’ll make use of this information.

LED’s as Varicap Diodes – Radio – LF/HF to Microwaves.

I’ve been wanting to put a ham radio into my car for quite some time. The obvious thing would have been to get a nice 2m/70cm dual bander, but I didn’t really want to invest a huge chunk of change into it at this time, so I decided to go with a simple basic 2m rig. My idea is that even if I decide to upgrade later, having an effective 2m rig lying around isn’t a terrible thing: I could use it for a base station radio, APRS, or even an uplink transmitter for the FM satellites.

So, I settled on the Yaesu FT-1900R. It’s inexpensive ($129) and I’ve had pretty good luck with Yaesu equipment. It was also the subject of a review in the May 2010 issue of QST which just arrived. (Incidently, that review is terrible. It is mostly a list of stuff that you can read directly from the product manual that you could just as easily download from Yaesu directly. I expect reviews to include some insightful commentary, not merely a laundry list of features. Additionally, the author chose to power this radio using the cigarette lighter adapter in his car. Everything I’ve read, from radio to car manufacturer guidelines tell you not to do this. It doesn’t lend a whole bunch of faith in the capabilities of the reviewer.)

I’ll probably bench test this radio when I get back home from Portland. Perhaps I can provide a more helpful review.

G4ILO had much better success than me with similar equipment. His mp3’s are way more convincing than mine.

G4ILO’s Blog: Arecibo success.

Or should that be maybe? Arecibo?

In the world of visual astronomy, it is well known that your eye’s peak sensitivity to light doesn’t occur right when you are staring at an object directly. To detect the faintest galaxies, you must stare slightly away from where the object is, and you’ll see it pop into view. This technique is called “averted vision”.

This leads to another phenomenon, which is detection through the use of “averted imagination”. You know a faint fuzzy is there, so you imagine that you see it.

While KP4AO was operating CW from Arecibo, I took my naked FT-817 outside with the cheapie 11 element cheap yagi I made, and aimed it where I determined the moon should be. And I heard… well…. something. I’d normally drag my laptop out with me to record, but I had my little Sony digital recorder, so used that instead. Here’s the audio, transferred back to my laptop (the file is a .WAV file, uncompressed, but the Sony does do some compression, so chances are this is slightly less legible than what I heard at the headphones):

Recording of Arecibo (???) from CM87ux using an FT-817 and a Cheap Yagi

I heard a few characters scattered in there, but maybe it’s my imagination. Tell me what you think!

Sigh. Not hearing anything from the Moon.

Tuning into the live ustream.tv video/chat line it appears that lots of people with much larger/better setups than me are also having difficulty hearing anything, so I am not the only one. Given that under the best of circumstances, my unproven antenna would have barely enough gain, I think this attempt has been somewhat unsurprisingly unsuccessful.

Sarah was nice enough to at least snap a picture of my standing out in front with my antenna, looking goofy.

12dbd (optimistically) ain't cutting it, even with Arecibo on the other end...

Addendum: It appears that they didn’t have their power amplifier up today, so were operating at a lower power level than was originally hoped. With luck, they’ll have that fixed and will be +13db tomorrow by comparison. I suspect that still might not be enough. But I’ll try again tomorrow, just in case.

So, my barely finished antenna got just one basic operational test last night. I monitored the pass of SEEDS II, which was squawking in Digitalker mode on 437.485, which is somewhat higher than the nominal frequency this thing is tuned for (it’s centered for operation around 432). I haven’t really tried SEEDS II in a while, so I can’t compare the relative signal strength, but at times the signals were quite strong, but I seemed to have difficulty tracking and had to keep rotating the antenna (polarization seemed to be shifting alot). I can’t remember its output power, but it must be quite low (well under 1 watt, 100mw wouldn’t be far off). I hadn’t heard it in FM/Digitalker mode before, so I wasn’t ready to record it, but I suspect I would have not had a great recording because of fading.

In about 30 minutes, a fifteen degree pass of AO-51 out over the Pacific will occur, and then in about two hours, Arecibo operations should begin. I’m carting my FT-817, a pocket recorder, some headphones and my antenna (probably toss in the Arrow too) and bringing them to work, and hoping I can hear something during a coffee break. Stay tuned.

Will I hear anything from the moon tomorrow? Your guess is as good as mine.

The business end of a Cheap Yagi

Apparently the Arecibo dish will be streaming video from their location during the Moonbounce event over the next few days. Check out the following link, or the embedded video stream:

KP4AO EME on USTREAM: Earth-Moon-Earth EmE transmissions from the Arecibo Observatory, the worlds largest radio telescope.. Science.

Okay, I’m stretching with this one: it’s a link to archive.org and their movie Le voyage dans la lune (A Trip To the Moon, or maybe A Voyage In the Moon) which is perhaps one of the very first science fiction movies, dating back to 1902. At the start of the 20th century, this was how people imagined a trip to the moon might occur. The same people who saw this film as young children could also have witnessed Apollo 11. Pretty amazing.

If you’d like a less fanciful source about the moon, you could try this NASA documentary on Apollo 11:

Okay, okay. The postings about computer checkers haven’t exactly been all that popular with you guys, so I thought I’d write up something that I am currently working on. Moonbounce Day is coming up April 16, 17, and 18, and I thought it would be a good opportunity to try to hear the station operating from Arecibo, Puerto Rico. I don’t have any equipment that does 70cm SSB/CW except for my trusty FT-817, so my idea is to just listen and record, and to use the minimal antenna that might conceivably work.

I of course continue to have my trust Arrow antenna, but I thought something a bit longer could be better. So, I have designed a DL6WU yagi consisting of a six foot insulated beam with 9 directors tuned for 432 Mhz and matched with a folded dipole/hairpin match. A trip to a local welding supply house netted me enough welding rod to make all the elements for $5, and another $3 netted me a nice six foot length of 3/4″ square hardwood to serve as the base. A few quick experiments last night showed that a miter box and a hacksaw could result in reasonably accurate cuts, but that maybe I should cut them 1mm long, and then trim them using my benchtop belt sander.

I’ll try to nab some pictures as it progresses. With any luck, by the end of the weekend I’ll have this mounted atop an old camera tripod, and I’ll be able to test it out a bit by maybe aiming it at some LEO sats and seeing how well it works. I’ll also have the complete dimensions later.

For now, coffee and breakfast.

Update:

Okay, here is the design that I came up with using VK5DJ’s Yagi Calculator. I specified an insulated boom 0.75″ in diameter, round elements 3.2mm in diameter, and a design frequency of 432 Mhz. One slightly annoying thing is that the design software only produces metric measurements, so I took them, wrote a little program to convert them into properly rounded values expressed in 1/32nds of an inch, and then dumped them all out. Here we go.

 338mm |  13 5/16" | Reflector
 327mm |   12 7/8" | Radiator (single dipole)
 305mm |       12" | Director #1
 302mm |   11 7/8" | Director #2
 299mm | 11 25/32" | Director #3
 296mm | 11 21/32" | Director #4
 294mm |  11 9/16" | Director #5
 291mm | 11 15/32" | Director #6
 289mm |   11 3/8" | Director #7
 287mm |  11 5/16" | Director #8
 285mm |  11 7/32" | Director #9
 686mm |       27" | Total folded dipole length
 343mm |   13 1/2" | Center of the dipole
 154mm |   6 1/16" | Center -> bend of the dipole 
 149mm |    5 7/8" | End -> bend of the dipole 
  25mm |  0 31/32" | Bend Diameter
  30mm |   1 3/16" | Boom position of Reflector
 169mm |  6 21/32" | Boom position of Radiator
 221mm |  8 11/16" | Boom position of Director #1
 346mm |   13 5/8" | Boom position of Director #2
 495mm |   19 1/2" | Boom position of Director #3
 668mm |  26 5/16" | Boom position of Director #4
 863mm | 33 31/32" | Boom position of Director #5
1071mm |  42 5/32" | Boom position of Director #6
1290mm | 50 25/32" | Boom position of Director #7
1519mm | 59 13/16" | Boom position of Director #8
1758mm |  69 7/32" | Boom position of Director #9

I cut the elements by marking the lengths, then putting them into a little plastic miter box and cutting them with a hacksaw. A few are very slightly long, so I’ll go back and fine tune those by a little judicious use of my benchtop belt/disk sander. I then turned to the boom. I must admit that on second glance, I’m not very happy with the hardwood boom: it’s got about 1/4″ of wave/twist in it as you sight down the length. But oh well, this is an experiment anyway. I marked all the positions, and drilled them out with a 1/8″ drill bit. This proved to be too tight of a fit for my elements, so I dug up a 9/64″ bit, which is very slightly too large, and allows some wobble. When I made a cheap yagi before, I secured these with hot glue, which is what I suspect I will do later.

That’s where the antenna stands now. I have to work on the driven element a bit more. Bending this by hand is a bit imprecise.

I’ll have pictures up when there is something to see.

Just a couple of quick notes for future investigation:

1. Milhouse uses a windowed search with a “soft-fail” alpha-beta search routine. If the value returned is outside a fairly narrow search range, milhouse re-searches the high region or the low region. These re-searches turn out to be incredibly slow. Not sure that I understand why that should be.
2. There are still some anomalies in detecting repetitions.

Addendum: Perhaps the first is a failure in move ordering?

The FCC has a notice of proposed rulemaking whose purpose would be to amend Part 97.113 to allow radio amateurs who are participating in government sponsored drills to be compensated by their employers. I am actually not a fan of this idea. While the Part 97 regulations acknowledge the value of radio amateurs to provide voluntary emergency communications, I think it represents a significant shift in the nature of the amateur service to allow a radio amateur to draw pay (even for emergency preparedness) while doing so. I suspect I’m in the minority, but I went ahead and filed my comments anyway:

My comments regarding Docket 10-72

I woke up at 5:30 or so this morning, and couldn’t get back to bed, so I thought some more tinkering with Milhouse was warranted. Musing about yesterday’s reading, I realized that I had a bit more work to really try it out: I’d need to write a code to handle regression learning. That seemed like too much, so I thought I’d play a quick game against Optime software’s Checkers Free for the iPhone. The program is little better than random play on its lowest setting: here’s a pdn file for the first game I played against it:

[Comment "Sparring Match Between Milhouse and iPhone"]
[Black "Milhouse"]
[White "iPhone"]
[Date "Sun Mar 21 09:25:13 PDT 2010"]
[Result "1-0"]
1. 11-16 22-18
2. 10-14 24-20
3. 16-19 23x16
4. 12x19 27-23
5. 8-12 23x16
6. 12x19 26-23
7. 19x26 31x22
8. 14x23 32-27
9. 23x32 30-26
10. 4-8 28-24
11. 6-10 26-23
12.  32-28 21-17
13. 28x26 22-18
14. 9-14 18x9
15. 5x30 20-16
16. 7-11 16x7
17. 2x11 29-25
18. 30x21

Milhouse brutalized it. Checkers Free goes off the rails at this rather elementary position at move 7…

White to move, with one move possibly equalizing, the other, to direct disaster.

The iPhone played 31×22, which is hideous: yes, you are exchanging down, but white’s position becomes horribly pinned, and you can’t help but give up material. Milhouse sees this easily in just 5 ply search.

Addendum: Cranking the iPhone’s settings up to maximum yielded a slightly better game, although still with a fairly lop sided outcome. I didn’t bother playing this one out to the end, while White has two kings, it basically can’t prevent red from marching down and getting a truly overwhelming advantage:

[Comment "Sparring Match Between Milhouse and iPhone on Highest Level"]
[Black "Milhouse"]
[White "iPhone"]
[Date "Sun Mar 21 10:30:56 PDT 2010"]
[Result "1-0"]
1. 11-16 23-18 2. 7-11 26-23 3. 16-20 24-19 4. 11-16 22-17 5. 9-14
18x9 6. 5x14 25-22 7. 8-11 29-25 8. 11-15 28-24 9. 3-8 31-26 10. 8-11
17-13 11. 6-9 13x6 12. 2x9 22-17 13. 9-13 25-22 14. 4-8 23-18 15. 14x23
27x18 16. 16x23 26x19 17. 20x27 32x23 18. 15x24 18-14 19. 10-15 14-10
20. 24-27 10-7 21. 27-31 23-18 22. 31-27 7-2 23. 15-19 30-26 24. 27-31
18-14 25. 31-27 14-10 26. 11-16 10-7 27. 27-23 7-3 28. 23x30 17-14
29. 30-25 22-18 30. 25-22 3-7 31. 22x15 14-10 32. 15x6 2x9

A fairly interesting position occurs for white on move 10. With white to play:

White to move: the iPhone played 31-26, but a better move exists...

Milhouse prefers 17-13, but only narrowly until the search depth approaches 20 ply, then it realizes that it might actually be a drawing move. I haven’t worked this out too much with Cake, but checking briefly, it seems that after 31 ply search, it sees the position as essentially drawn. Milhouse would take probably the better part of an hour to reach that search depth.