Quiz Question for Knack Victims

Hey Bill,

I know you have the knack . . . so I'm coming to you.
I've got 31 years of ham radio experience, on top of 16 years experience in the Wireless Telecom industry, that said I have a tech question that has really got me stumped. Maybe the answer is just too obvious.

Here it is: About 2 years ago an electrical engineer/ham radio operator/nuclear engineer threw the following question by me (I've yet to get back to him with my answer). Maybe you, or some of your listeners know the answer.

Knack Question: For yagi antennas only one (yes, sometimes two) element is electrically driven/xmit. Instead, why aren't all of the elements (simultaneously) electrically driven/xmit (vs parasitically driven)? Now the stumper - according to the engineer supposedly the answer excludes the following as the answer(s):

• Impact to antenna gain,
• The need to have any type of phasing harness
• Impact to transmit horizontal beam width (directivity).

Any idea what the answer might be? What am I missing?

QRSSing again, AA1TJ's new page

As I mentioned earlier, computer problems have delayed the SolderSmoke podcast (don't worry, parts are on the way).  They have also knocked me off the WSPR system.  So I switched over to QRSS mode and am now pumping out about 20 milliwatts of upside down sloooooooooow FSK on about 10140050 Hz.  (Don't you like how in QRSS you find yourself giving the frequency not in kilos or megas, but in just plain Hertz?   If I get into a retro mode I may start giving them in cycles.) During daylight hours in Europe you should be able to watch my little signal arriving at ON5EX's station in Belgium.  Just look down on the right on this page for a live view of Johan's receive screen.


VA3STL has some good QRSS stuff on his blog:  http://va3stl.wordpress.com/



I noticed this morning that Mike, AA1TJ has moved and updated his very fine site.  Check it out: 
http://www.aa1tj.com/radio.html
Be sure to click on the link that lead to info about Mike mountain-top work site.  Like I said, truly the kind of job that Knack victims dream about.

Rumor has it that Dan's Small Parts is back in operation after a winter break.

More Mars (with olive oil)

No podcast this week. I have two excuses: 1) Computer problems (a long, sad story), and 2) we were once again out in the Sabine Hills. Above is another look at the olive grove QTH. That solar panel thing on the right is an automatic weather reporting station installed by the Region of Lazio. Those trees behind the weather station are olive trees.

We had clear skies this past weekend, and with Mars approaching full opposition, I had the telescope out. We got some better views of Mars than we had last week. When the atmosphere (ours!) would settle down a bit I could make out some of the dark "canali." The Northen polar cap was very visible. The moon was bright (first quarter I think) and so I was wondering if we'd be able to see the M31 galaxy in Andromeda. Even with the moon close in the sky, I had no trouble finding the galaxy using my old Soviet-made 7X50 binoculars. We also looked at the North America nebula in Orion's sword (very appropriate as we had Canadian friends with us).

My telescope (above) has a simple but effective Dobsonian mount. (This system is named for the amateur astronomy guru John Dobson -- interesting guy.) The 'scope basically slide on teflon pads. These pads need a bit of lubrication from time to time. Mine were getting a bit sticky, so I started to look around for something to to grease the teflon. The solution was literally all around me:

Worked like a charm!

Also got on the air with the HW-8 and worked stations on 80, 40, and 20, including two QRP stations.

Does Math Lead to Understanding?

In "SolderSmoke -- The Book" I describe the quest for deep understanding of the circuits that we build and use. There is some discussion in the book of the role of mathematics in this quest. A while back a reader e-mailed me on this subject. In the hope of stimulating a discussion, I'll present the key paragraph from that e-mail here (the author will, for now, remain anonymous):

I appreciate your quotes from Feynman, Asimov, etc. about not
really being able to fully understand everything. As a math teacher
I can say that one of the biggest misunderstandings about math
is that it "explains" the phenomena of physics and engineering.
(Science and math teachers are notorious for saying to a student
who has just asked a "why" question things like, "well the math is
a little bit more complicated than what you can handle right now.
Wait untilyou have had a year or so of calculus.") In reality it's
the exact opposite! The math equations actually hide the answers.
They are very good at accurately describing phenomena, or at
predicting what will happen next, but they can never answer the
question of why one equation works and another does not. We
get very comfortable with allowing the familiar math equations
to hide our inability to really answer the "whys."

This really resonated with me. In my effort to get a better grasp of mixer theoy a lot of people seemed to be simply pointing me to the trig equations, and equating a knowledge of those equations with an understanding of how the mixer circuits really work.

Of course, I don't mean to be anti-math here, but I thought the e-mail on the limits of mathematics was very interesting. In "Empire of the Air" Tom Lewis wrote, "At Columbia, Edwin Howard Armstrong developed another trait that displeased some of the staff and would annoy others later in life: his distrust of mathematical explanations for phenomena of the physical world. All too often he found his professors taking refuge in such abstractions when faced with a difficult and seemingly intractable conundrum... Time and again as an undergraduate at Columbia, Armstrong had refused to seek in mathematics a refuge from physical realities."

My QSO with K4TWJ

Like everyone else I was saddened to hear of the passing of Dave Ingram. We've all been inspired by Dave's magazine articles, columns, and by his books. I'll always remember his QRP transmitter in a pen!
It was my privilege to talk to Dave once, on the air. I was on 30 meter CW with a brand new,scratch-built, HB QRP transceiver. I was in Virginia. I recognized Dave's call, and was thrilled when he came back to mine. I told him I was running homebrew QRP, and that I'd found inspiration in his articles. I know he was happy to hear that.
73 OM!
Dave's wife Sandy put a nice message on his blog: http://k4twj.blogspot.com

Some Real DX: Andromeda Galaxy, M31

I mentioned that Billy and I had spotted the Andromeda galaxy. The photo above (not by us) is sort of close to what we saw. The astronomy books usually show these spectacular images of Andromeda in all its glory. But those pictures come from long exposures through big telescopes. Through our little six inch reflector, Andromeda looks like a cloud, not quite as defined as the one in this picture. This picture is a 4 minute exposure through an ordinary digital camera using a 300mm telephoto lens.
(From: http://www.prairiehillfarmiowa.com/prairiehill/Home.html)

It is a real thrill to look at Andromeda. That little cloud represents 300 billion stars, and they are around 2.5 million light years away. So when you look, you know the photons hitting your retina started their trip LONG before there were homo sapiens. Icing on the cake: A satellite went through the telescope's field of view just as was looking at M31.

Another nice thing about Andromeda galaxy is that you can see it with the naked eye (you have to know where to look!). Because of this, people have been observing it for quite some time. Here is the first known drawing of M31. This is the work of the Persian astronomer Al-Sufi, and was done in year 964. The Persians imagined a constellation in the form of a fish in that part of the sky. Note the little cloud near the mouth of the fish -- that's M31.

Until 1923 astronomers thought M31 and other "nebula" were just clouds within our galaxy. The thought was that the Milky Way was the only galaxy. But then Edwin Hubble got some distance readings (using variable stars) on Andromeda and realized that he was looking at an entirely separate galaxy. That was a BIG discovery.

Homebrew transistors, QRSS Blog, Shep Show, Nose as toubleshooting tool

Some odds and ends today:

Ed, KC2TYP alerted me to this one: Jeff, K7JPD, has a very intriguing blog post about homebrew transistors. I suspect AA1TJ will have a rig made of these things on the air within a week. Check it out:
http://jeff-duntemann.livejournal.com/227856.html

There is a new blog for the Knights of the QRSS:
http://knightsqrss.blogspot.com/

Dave in Ireland sent me a link to the Jean Shepherd show in which he discusses his first soldering iron: http://www.archive.org/download/JeanShepherd1975/1975_07_30_Soldering_Iron_full_show.mp3

Alan, WA9IRS, alerted us to a nice EDN article on using your nose as a trouble-shooting tool:
http://www.edn.com/article/CA6713738.html