Saturation and Class C Amplfier Efficiency

Originally posted on Gadgeteer News: 10 December 2006

FIRST LTSPICE VIDEOCAST

I made a 5 minute video using a video screen-capture program and the circuit simulator LTSpice. In addition to showing how LTSpice can
be used, the video looks at how saturation affects the efficiency of Class C amplifiers. I put the file on YouTube, but the video quality is poor when viewed through that service (it is difficult to see the graph lines in the YouTube version). So I have also uploaded the 26 meg file (.wmv)
to the http://www.gadgeteer.us web site.

Click here for the direct download of the .wmv file

Click here for the YouTube (lower quality) version

Thoughts on Minimalist Radio

I had a lot of good articles on the old web-page version of this blog. I want to get them into the index, and the only way I can think of to do this is by posting them again. I don't think this is a problem: many readers will have never seen them, and even for those who have, many of these are so good they deserve a second look. This 2006 piece by KK7B is a good example (The picture is from Roger, KA7EXM's FDIM 2007 photo collection and shows KK7B winning a toroid winding contest):

A FEW THOUGHTS ON MINIMALIST RADIO FROM KK7B
(Originally posted on the EMRFD Yahoo group)

If you really want to do minimalist radio, you may want to step way
back and take a look at some very early history. The Pixie circuit
has many more components than an early CW station from the era
immediately after spark.

Rather than starting with the Pixie and trying to figure out what to
eliminate, maybe a better approach is to start from zero and decide
what you need. Combining transmit and receive functions is the last
thing to think about.

Starting with the receiver.... The first thing you need is wire up
in the air. The more, the better. If you have the real estate for a
full sized dipole on 80 meters, you can collect enough signal energy
to hear on a crystal set when conditions are good. I've copied CW
signals on 40 meters with just a dipole, transmatch, a 1N34 diode, a
good pair of headphones, and a one transistor Pierce oscillator
running on the bench. The leakage from the crystal oscillator picked
up by the antenna beats against the incoming signals. I didn't power
the oscillator with lemon juice, but I could have (see Bob Culter and
Wes Hayward, "Lemonized QSO" in March 1992 QST.)

Then for the transmitter, just heat-sink the Pierce oscillator and
key the connection to the load. The shift in load impedance will
offset the crystal oscillator frequency.

A dual pi-net transmatch configuration would take care of the
harmonics and allow maximum energy transfer between the antenna and
diode--but I'd analyze it to make sure the harmonic suppression is
more than legal.

So far I count 5 components for the dual Pi-Net transmatch, a 1N34
diode, 6 components for the one-transistor Pierce oscillator. A
dozen parts, plus headphones, a key, and battery--or some electrodes
to push into a lemon.

That would make contacts, but Wes and I have discussed a basic rule
for radios, which is that a station should be able to work an
identical station over a distance of a few miles. It could probably
be done with the above station, but a single transistor audio
amplifier running at maximum gain between the 1N34 and headphones
would make it possible to extract many more signals from the 80 meter
dipole. That's another 5 or 6 parts. So now I'm up to about 20.

For a more serious station, I'd probably add two more transistors and
a diode, so I could have a separate PA, a balanced mixer, and two
audio stages. The receiver would end up looking a bit like EMRFD
figure 8.7 with a PA tacked on. That would have about 35 parts, but
it would be able to work DX off the ionosphere...about the same
complexity and performance as many other variations on the theme. A
previous version of the Pixie from the 1970s was called "The
Optimist."

Unlike Muntz--instead of starting with someone else's circuit and
trying to eliminate parts until I had something that just barely
works, I'd start from scratch, study EMRFD (and other references too--
but in EMRFD all the circuits have been designed and tested) for
circuit ideas, and then start experimenting on the bench, one stage
and one component at a time. Since one of the joys of minimalist
radios is that they can be understood all the way down to the device
physics, I avoid ICs. (I particularly avoid cell-phone ICs, which I
designed for a number of years. It's like working in a sausage
factory--you are much happier if you don't know what's inside.)

Minimalist radio is one of the more interesting design games that we
play using the methods of EMRFD. It's cheap, it's interesting...and
as we dig in, we discover that the details can be every bit as
challenging for a radio project with 30 parts as one with 30,000.

Have fun.

Best Regards,

Rick kk7b

In Rotterdam

I'm up here with Billy on a violin gig. Beautiful place! Will descrbe
on next podcast. 73

Radio Signals from Jupiter and Io on 17 Meters

Jupiter and Io montage captured by the New horizons spacecraft.
The Jupiter image is false-color near IR data obtained with the LEISA instrument, built at GSFC.

I try to always read the QRP-L postings of NA5N -- Paul always has something interesting in his messages. Today I found this:
Jupiter emissions peak around 18-22MHz; they are a function of when the moon Io crosses certain longitudes of the relatively fast spinning Jupiter. There used to be a couple of calculators online (haven't checked lately) as to when the L-bursts should occur. The timing is quite predictable; detecting them on every predicted occurrence is not. You have to have an antenna with a little bit of gain. The signals are generally weaker (that is, near the atmospheric noise level) than can be detected with a dipole. With a fairly decent setup, the Jovian L-bursts sounds like ocean waves crashing on a distant beach, just barely above the noise level. The S-bursts sounds like random pulse type static in short bursts. These are harder to detect than the L-bursts.

I had known about the Jovian radio emissions, but I didn't know that the moon Io was involved. For me, Io's involvement somehow makes this even more interesting. Jupiter and its moons (including Io) are some of the few celestial objects I can regularly see from central Rome.

Here is a good description of Jupiter's radio signals, and Io's role in transmitting them:
http://radiojove.gsfc.nasa.gov/library/sci_briefs/decametric.htm

And here is an interesting article about the discovery (50 years ago) of these signals:
http://radiojove.gsfc.nasa.gov/library/sci_briefs/discovery.html

SolderSmoke Podcast #108

http://www.soldersmoke.com

In SolderSmoke 108:

May 24, 2009
Hubble Space Telescope Repair Mission
WSPR: W3PM sees my sigs, back to visual (briefly), on to Slow Hell.
Ubuntu ham radio software
Time nuts
Jean Shepherd gets his Class A license
"SolderSmoke -- The Book" Good for summer vacation reading.
SPECIAL REPORT FROM DAYTON - FDIM BY BOB W8SX
MAILBAG

CHECK OUT THE BOOK: (First chapter preview available)

http://www.lulu.com/content/paperback-book/soldersmoke/6743576



73 from Rome

Tech Details on ET's "Phone Home" Beacon Rig

Mark "MOJ" Johnson, W8MOJ, sent me a really amazing 73 Magazine article. It is from the APRIL 1983 issue. (The month of publication set off my April-fool alert alarm, but this is for real.) When Steven Spielberg was making ET, the producers contacted Bell Labs and asked for help in designing the rig that ET would use to phone home. A ham, Henry Feinberg, K2SSQ, got the job. In the article, Henry wrote: "What Spielberg wanted was a beacon transmitter, something to say, 'Here I am, Come and get me!' I reasoned that three main parts wee needed for a basic beacon: a means of producing a message, a programmer to repeat the message, and a way of transmitting the signal into outer space."

Later, in describing the keying device, Henry wrote: " The surface of the saw blade was coated with several layers of spray paint, which served as insulation, preventing the bobby pins from contacting the metal blade. The message was programmed on the blade by carefully etching through the paint. "

OK, that does it. Time for me to go back to the Trastevere flea market to pick up some more cheap clock drives... and maybe some circular saw blades. I need to get going on my mechanical QRSS one-transistor becaon project.

REAL Hams Make Their Own Crystals....

Bill: You say you buy your crystals from the electronics store? Real homebrewers grind their own crystals. See attachments. Russ

After reading this I was feeling like a complete APPLIANCE OPERATOR. But wait a second Russ -- that's a KIT! Real homebrewers don't need KITS to make their own crystals! And remember, you are talking to a guy who has used iron pyrite and a phosphor bronze to detect radio waves. That means I have homebrewed my own DIODES! ;-)

Thanks for the cool pictures Russ. Those were the days...

Seeing my WSPR signal

Graham, G3ZOD, sent me this WSPR screen-shot. He writes:

Hi Bill. Thought you might be interested in a screen grab of yourself. You're the near continuous signal along the centre of the waterfall just below 200 on the vertical axis.Not DX from Italy to England, but I'm using an indoor wire antenna and I usually receive you for short periods only - never seen such a consistent signal before. By the way: I think your computer clock may be a couple of seconds off according to the DT values; I have mine resync every 6 hours and my clock is generally within 150 milliseconds.
73 de Graham G3ZOD

Thanks Graham! The consistency of my signal is no doubt due to the fact that I have no receive system here yet, so on the WSPR software, in the "T/R Cycle" box I had "TX" checked. So I was "key down" most of the time. Your screen shot made me realize that this might not be the most neighborly thing to do -- someone else on the same freq might be QRMd by my 20 mW DSB sig. So I think I'll ratchet down the T/R cycle here.
My computer clock is erratic. I have to tweak it each day. I know there is a program out there that automates this -- haven't gotten to that yet. 73 From Rome

Shep's Class A License, Part II

I didn't mean to leave you guys in suspense. Here is the exciting conclusion.
EXCELSIOR!

Jean Shepherd Gets His Class A License

I was drifting off into Linux-land, but an e-mail from OM Gene, K8EE, brought me back. I'd thought that we had already unearthed all of the best ham radio episodes of the Jean Shepherd shows. WRONG! K8EE sent me YouTube recordings of the January 7, 1964 show on WOR New York. Gents, all I can say is that you should stop what you are doing, and listen to this. (And don't miss the exciting conclusion in part 2!)

"Mr. Rupp, what do you know about the Mu of an '807?" Indeed.

Ubuntu

As SolderSmoke listeners know, I'm not really a software guy. In fact, I'm only a marginally competent user of software. But I've taken a liking to Ubuntu Linux. It works, it is user friendly, and it seems to have developed a very cool African cultural thing around it. Check out the names of the various versions and you will see what I mean:

4.10 Warty Warthog
5.04 Hoary Hedgehog
5.10 Breezy Badger
6.06 Dapper Drake
6.10 Edgy Eft
7.04 Feisty Fawn
7.10 Gutsy Gibbon
8.04 Hardy Heron
8.10 Intrepid Ibex
9.04 Jaunty Jackalope
9.10 Karmic Koala (NEXT ONE) October 2009

OK, now back to the radios...

KO7M Suddenly Goes Manhattan

Perhaps he picked up the vibrations from Dayton and FDIM where they were conducting a Sudden Receiver build-a-thon... Jeff, KO7M, (aka the lucky guy with the Piper Cub) recently tried out Mahanttan-style construction -- he built an NE602-LM386 Sudden Receiver... and liked it.

Jeff writes:

Believe it or not, I have never built anything Manhattan style… So, I decided to give it a go and built a little 40m DC receiver designed by Rev. George Dobbs G3RJV consisting of a NE612 and LM386. I have included a shot of it below. I was very pleased with this building style and think I may adopt it going forward. In particular I like how easy it is to make changes. I just used tin snips to make the pads. For the 8 pin IC pads, I cut them 2 cm square and used a hacksaw to saw between the IC pins and up the middle to separate the pin pads electrically by removing the copper. Make sense? Very simple to then bend the IC pins 90 degrees and solder them down. Preaching to choir, I know… But it takes some us a little longer to get on board, eh? J I was very pleased with the outcome.

I like Jeff's technique for the IC pads. I will have to try that.

SolderSmoke 108 will feature an interview with George Dobbs in which he talks about the Sudden Build-a-thon.

W3PM Hears the WSPR Rig he Inspired

I got a nice e-mail from Gene, W3PM. Gene's simple homebrew SSB rig for WSPR provided the inspiration that got me into the WSPR mode. We'd been exchanging e-mails a while back, then he mentioned that he would be away... Turns out, he ended up within range of my 20mW WSPR sig. (The picture shows Gene doing some maritime mobile satellite operating from the QEII in 2002.)

Hi Bill, I just wanted to let you know that I hear your 20 mW WSPR signal each morning around 0500 to 0700 UTC. Your signal strength varies between -21 and -26 dBm.

I am currently on vacation in Fettercairn (GM4YRE, IO86ru), Scotland which is located about 30 miles SW of Aberdeen in the northeastern part of Scotland. I have very limited internet access; therefore, I cannot report WSPR spots in real time. My WSPR transmitter is active most days on 30 meters until we leave Scotland... I run one watt to a low doublet antenna.

73/72 Gene W3PM GM4YRE

Atlantis, HST in Front of the Sun

Check out the little black marks in the lower left of old Sol. That's Shuttle Atlantis and the Hubble Space Telescope (you can see it in more detail below). The picture was taken from Florida by Thierry Legault. He calculated when the spacecraft would be aligned with the sun from his Florida location and took the shot. Well done. More innovative astrophotography at his site: http://www.astrophoto.fr/ Note: Too bad we don't see any REAL sunspots!

Scary Stuck Bolt on Hubble Space Telescope

They had a scary moment during yesterday's space walk. They were trying to get the old camera out. One of the bolts wouldn't turn. It has been in space for 16 years They kept adding more torque, and they knew they were approaching the point at which the bolt would break, preventing -- forever -- the replacement of the camera. In what looked like their last attempt, the got it turning. Bravo! The live coverage via NASA's online TV is really superb. They are using helmet-cams, and you get to see just what they see.

NASA put together a video on the personal stories of the crew members. I think it is a good thing to show kids (Billy has already seen it, Maria is next):

Fixing the Hubble Space Telescope

Gentlemen, NASA TV is the place to be this week. They have the Hubble Space Telescope in the payload bay of the Shuttle and soon they will be going outside to do the kinds of repairs that Knack victms can relate to. (Update: I'm watching a space walk live through the helmet-cam of Astronaut Grunsfeld. They are now lubricating some bolts on the doors of the telescope.)

Here is the NASA description of the repairs.

Two of Hubble's instruments are in need of repair. ACS, which partially stopped working in 2007 due to an electrical short, is the "workhorse camera" responsible for some of Hubble's most spectacular images. STIS is a spectrograph that sees ultraviolet, visible and near-infrared light, and is known for its ability to hunt black holes. While COS works best with small sources of light, such as stars or quasars, STIS can map out larger objects like galaxies. STIS suffered a power failure in 2004 and was put into hibernation to preserve the possibility of its repair.

Astronauts plan to fix both – a challenging prospect since these repairs are beyond the scope of Hubble’s serviceable design. Hubble’s creators envisioned astronauts swapping out components, not performing delicate surgeries during spacewalks.

An interior electronics box of ACS that supplies power for ACS detectors, contains equipment affected by an electrical short. However, its location makes it inaccessible to astronauts. So instead of trying to reach the problem area, astronauts will attempt to bypass those power-shorted components entirely.

The failed power supply is connected by cables to a series of electronics boards, which are within reach but have no power because of the damaged box. Astronauts will install a new power supply to a handrail on the ACS outer enclosure, remove the electronics boards and install different ones that are compatible with the new power supply, and connect them to the new supply with exterior cables. The arrangement simply cuts the damaged box out of the equation.

Innovative tools for the repairs are designed and developed by Goddard engineers and tested by the astronauts for refinements. STIS needs a new power supply circuit board. The repair would be relatively easy but for the electronics access panel, which was never meant to be opened and is attached to STIS by 111 small screws. The screws are hard to grasp with the astronauts' gloved hands, and could create problems if they were to escape and float around the electronics. So engineers have created a "fastener capture plate" that fits over the top of the panel. When the astronauts remove the screws, they will be trapped in the plate. Astronauts will then switch out the power supply circuit board and close off the open electronics with a new, simpler panel that attaches easily with two levers.

3 Kids, 3 Cesium Clocks, Mt. Rainier, Time Dilation

He may not know it, but this dude has a bad case of The Knack. From his web sites:

In September 2005 the kids and I took several very accurate cesium atomic clocks from home and parked 5400 feet up Mt Rainier (the volcano near Seattle) for a full two days. The goal was to see if the clocks actually gained time, even if billionths of a second, as predicted by Einstein's general theory of relativity. Does gravity really alter time and can this weird phenomenon be detected with a family road trip experiment?

Ten years ago I wanted to build a LED digital analog clock that would be accurate to better than one second per year -- so I would have the fun of adjusting it when a leap second occurred. This simple goal resulted in a most interesting journey into electronics, horology, astronomy, test equipment, quartz oscillators, rubidium and cesium atomic clocks, hydrogen masers, frequency counters and phase comparators, GPS, Loran C, GOES, and WWV / WWVB radio receivers. That makes me one of the Time-Nuts. By now I've exceeded that goal by a factor of a million: the best clocks in my collection (active hydrogen masers) are accurate to better than one microsecond per year. Excluding national government laboratories, my home time lab now has the most accurate clock in the world.

For info on the Rainier Time Dilation Road Trip: http://www.leapsecond.com/great2005/tour/
For a more general discussion of this madness: http://www.leapsecond.com/

Hey, but who are we to talk, right?

SolderSmoke Podcast #107

http://www.soldersmoke.com

On SolderSmoke 107:

SolderSmoke -- The Book!  ON SALE NOW!
Get it here: SolderSmoke: A Global Adventure in Radio Electronics

Orbits II reborn via a VK6 junkbox
NA5N's Amazing Atlanticon 2002 article
WSPR madness:
20 mw across the Atlantic.
K1JT picks up my sigs
WSPR generates interest on Hack-A-Day
Linux: Ubuntu gets SolderSmoke Thumbs-up
Somerset Supper Report
Diode Ring Mixers
Solar conditions
AA1TJ, Chloroform, and HB transistors
ET's rig
Have fun at FDIM!
MAILBAG

SolderSmoke -- The Book! On Sale Now!

SolderSmoke is the story of a secret, after-hours life in
electronics. Bill Meara started out as a normal kid, from a normal
American town. But around the age of 12, he got interested in
electronics, and he has never been the same.
To make matters worse, when he got older he became a diplomat. His
work has taken him to Panama, Honduras, El Salvador, the Spanish Basque
Country, the Dominican Republic, the Azores islands of Portugal,
London, and, most recently, Rome. In almost all of these places his
addiction to electronics caused him to seek out like-minded radio
fiends, to stay up late into the night working on strange projects, and
to build embarrassingly large antennas above innocent foreign
neighborhoods. SolderSmoke takes you into the basement workshops and
electronics parts stores of these exotic foreign places, and lets you
experience the life of an expatriate geek. If you are looking for
restaurant or hotel recommendations, look elsewhere. But if you need to
know where to get an RF choke re-wound in Santo Domingo, SolderSmoke is the book for you.
SolderSmoke is no ordinary memoir. It is a technical memoir. Each
chapter contains descriptions of Bill’s struggles to understand (really
understand) radio-electronic theory. Why does P=IE? Do holes really
flow through transistors? What is a radio wave? How does a frequency
mixer produce sum and difference frequencies? If these are the kinds
of questions that keep you up at night, this book is for you.
Finally, SolderSmoke is about brotherhood. International,
cross-border brotherhood. Through the SolderSmoke podcast we have
discovered that all around the world, in countries as different as
Sudan and Switzerland, there are geeks just like us, guys with
essentially the same story, guys who got interested in radio and
electronics as teenagers, and who have stuck with it ever since. Our
technical addiction gives us something in common, something that
transcends national differences. And our electronics gives us the means
to communicate. United by a common interest in radio, and drawn closer
together by means of the internet, we form an “International
Brotherhood of Electronic Wizards.”

http://www.lulu.com/content/paperback-book/soldersmoke/6743576

Homebrew Transistors? Careful with the Chloroform!

I suppose it was inevitable. After years of pushing the envelope with the tunnel diode, it seems like Michael, AA1TJ, is moving toward homebrewing his own transistors. Michael writes:

Hey, I found a Yahoo Group of kindred spirits late last night, 2N1150_Down; where the interest is centered on early Germanium semiconductor devices. I downloaded a book from their files that, until now, I'd only heard about. Practical Transistors and Transistor Circuits, by J.S. Kendall, first appeared in the U.K. in 1954. Believe it or not, the subject of the book is how to make the "practical" transistors referred to in his title! Of course, these are point-contact devices built from a pair of cat's whiskers on a slab of "P-type" Germanium salvaged from diodes. I especially like where he writes, "Great care should be exercised owning to the anesthetic properties of the chloroform vapour...the constructor may not be aware of the danger until he is almost on the point of collapse." Oh brother!

Better yet, I found an article in the group's files taken from the March and April, 1954 issues of The Short Wave Magazine, by G3HMO. This fellow not only made his own transistor, he used it to build a one-transistor, 160m, transmitter and then went on to make contacts with it up to a distance of 30miles! He writes, "There is nothing impractical about making a point-contact transistor at home." Oh baby, crack me open a bottle of chloroform and let's get to it!

The photo above is, of course, the original point contact transistor from 1947. It looks do-able.
In searching for the picture I came across this interesting article from the author of the wonderful book on this subject "Crystal Fire" : "How Europe missed the Transistor"