SolderSmoke Podcast #109

http://www.soldersmoke.com

June 7, 2009

Violin gig in Rotterdam
June 2 Parade in Rome
Why do we use Rl=Vcc^2/2Po for Class C amps?
     NA5N article, EMRFD, SSDRA, LTSpice
Radio Signals from Jupiter and Io (on 17 meters)
VK2ZAY's X-Rays
Jeff Damm, WA7MLH:  Homebrew Hero
Tim Walford's Constructor's Club:
     Floor Polish as PCB Laquer
     Numbers Stations (very timely!)
SolderSmoke -- The Book: Very rapid delivery, even to UK
MAILBAG

The Look of a True Radio Homebrewer

Jeff Damm, WA7MLH, is one of our gurus, a high priest of The Knack. I visit his excellent site from time to time, just on the off chance that he will have posted something new. This morning I was rewarded with this picture from 1988 -- I think it somehow captures the spirit of the true radio homebrewer. Check out all the homebrew gear. Note the copy of SSDRA on the operating table. Jeff assisted with the construction of many of the projects in that book. He helped free us from the tyranny of excessive neatness and right angles, and let us know that ugly circuit construction works just as well.
Here's Jeff's FB site: http://www.neoanderthal.com/wa7mlh1.html

Walford Electronics

Tim Walford, G3PCJ, offers a really nice line of ham radio kits. I like the names of the products, and of course I really like the DSB kits. The photo above is the workbench on which these rigs are created. Tim also runs a Construction Club and puts out an excellent quarterly newsletter called "Hot Iron." I just received the latest issue, which is a particularly good one -- more about this in SolderSmoke 109.

Here is a list of Tim's kits:

AMU Matching bridge and T match for 10 - 160m
Audio Amplifier General purpose amplifier for driving a loud speaker
Audio Extras Adds AGC and good CW facilities to a phone TCVR
Brendon Small DSB 1.5W phone transceiver for 80m
Brent Small 1.5W CW transceiver for 80m
Chirnside Regen RX, crystal controlled AM TX, for any band to 6m
5D Counter Five digit frequency readout
Dual Low pass filter Pair of relay selected Low Pass Filters
Fivehead Single band 1.5W SSB phone TCVR for 20 - 160m
Kilmot Double sideband 80m 1.5 W phone TX
Kilton 1.5 Watt CW TX - 20 to 80m
Kingsdon 5 Watt phone SSB and CW transmitter to go with Midney
Knapp Single Band regen TRF - 3.5 to 15 MHz
Knole Single Band DC RX, 20 to 80m
Linear 10 Watt RF amplifier for all nominal 1.5W rigs
Midney Simple single band superhet RX for any band 20m to 160m
Mini mix Mixer kit for VFO schemes or as receive converter
Notch filter Variable frequency notch or peak audio filter
Speech processor Boosts average signal level under difficult conditions
Trull Medium Wave regen TRF for newcomers, can also do HF
Two Tone oscillator Provides audio tones for setting up SSB rig
Washford Crystal controlled 1W CW TX for 20, 40 and 80m
Willet Simple direct conversion RX for 20, 40 and 80m

Here is the website of Walford Electronics: http://walfordelectronics.co.uk/

NA5N on the NE602

I continue to mine the Gadgeteer News archives.
Here is a good one from NA5N.
Orignally posted on Gadgeteer news, 2 December 2006

NE602=NE612=SA602
(Originally posted by NA5N on QRP-L)

Gang,
The ever famous NE602's are manufactured in the Philips
Semiconductor plant in Albuquerque, about 85 miles north of me. I visited
there last summer and had a nice discussion with an applications engineer
about the history of the NE602's. Goes something like this:

This long story will prove that NE602 = SA602 = NE612 = SA612
(for those of you who don't want the gory details -hi)
The original NE602 was designed/manufactured by SIGNETICS for
the 45MHz FM wireless telephone market. A little later, the wafer was
redesigned a bit to allow the internal oscillator to operate to 200MHz and the
RF to 500MHz. This was redesignated the NE612, and was intended to
replace the NE602. However, customers kept ordering the NE602, getting
angry at Signetics because their distributors were out of stock, etc. So when
they made the chips, they made a jillion NE612's, and labeled some of them
NE612 and the rest NE602 to satisfy the users of both parts. This is why
contemporary data books show the exact same specifications for both NE602
and NE612. They came from the same wafer.

Then Signetics was bought out by Philips, who evidently
continued this practice for a short time, then decided it was rather
redundant. So they announced that the production of NE602's has been discontinued
and listed it as an obsolete part ... giving QRPers around the world
various fits of apoplexy to suicidal tendencies that doomsday had struck.
What wasn't well understood is Philips continued to support production of
the NE612, as they do today.

Then to make matters worse, disaster struck the Philips plant
in Albuquerque in the spring of 2000. A wild grass fire in
northwest New Mexico threatened three main electrical lines that run from
the "Four Corners" electrical generating plant to Albuquerque. Smoke
from the fire caused one of the high-voltage lines to arc, tripping the
circuit off line. Virtually the entire electrical load for Albuquerque
and southern New Mexico was now transfered to the two remaining feeders,
which could not handle the full load, causing brownouts, voltage spikes,
etc. until they too failed. Where I live in Socorro, New Mexico, I
remember the brownouts hit about 4:15pm, outages on and off until the
entire grid went down about 5pm, and stayed off until about 11pm. One of the
longest power failures in US history. We just figured it was Y2K about 3
months late. (PS - I worked 40M CW QRP that night by candlelight, and it
was the quietest conditions I ever heard on 40M!!! And every QSO I
heard seemed to be a QRPer). The extreme voltage fluctations as the
feeders were failing caused a transformer at the Philips plant in
Albuquerque to catch on fire. I remember seeing it on the TV news, in which they
said it caused mostly smoke damage from the burning transformer and
burned a couple of storage rooms. That was all-no biggie. Well, it
turned out one of the storage rooms that was burned was where they stored
the film masters for making the semiconductor dies, and the NE612 film
master was now molten emulsion. These film masters were the originals
from the old Signetics company. So Philips had to completely redo the
artwork for the majority of their IC's. Additionally, it turned out the
smoke damage was excessive and the IC fabrication facilities were
left unusable. Philips was basically unable to manufacture IC's at
the Albuquerque plant for months. It was about 8 months before
they got all their wafer machines back on line, which left a huge hole in
the semiconductor industry. I know it just about killed several
cell phone manufacturers because delivery contracts for parts were
suddenly postponed for six to eight months.

The world wide supply of NE602/NE612's virtually dried up
during 2000 as a result of this fire and the nearly year backlog of
manufacturing quotas. The first run of NE612's in 2 years finally occured in
September 2000.This huge shortage of NE612's, combined with the fact that
NE602's have been discontinued/obsolete, is what convinved QRPers that
these nifty little chips were no more. I was told 20,000 units were
manufactured in 2000, or what Philips believes is a 2 year supply. This is
also why the release of the K1 (with 5 NE612's!) was delayed from the
promised "after Dayton" to late in the year, as were other kits. It just
wasn't clear when Philips was going to schedule the NE612's for production.

So yes, the NE602 is dead, but the perfectly compatible NE612
is still available, and Philips has no plans at the present to
discontinue that part number.

For final clarification:
NE602 = plastic DIP, rated 0C to +70C ... OBSOLETE
SA602 = plastic DIP, rated -40C to +85C ... OBSOLETE
NE612 = plastic DIP, rated 0C to +70C ... AVAILABLE
SA612 = plastic DIP, rated -40C to +85C ... AVAILABLE

or, to answer the final question ...
NE602 = SA602 = NE612 = SA612

72, Paul NA5N

Alan Yates Making X-Rays from Rectifier Tubes

Anytime you find yourself writing a sentence like this...
"At only 20-30 kV and a few hundred uA in cold-cathode mode the x-ray radiation pours out, making the end-window Geiger counter scream from more than a meter away."
... perhaps some alarm bells should be going off.

Our friend Alan, VK2ZAY, has been busy in the lab, generating X-Rays from old 2X2 rectifier tubes. This reminds me of one of the articles in the wonderful C.L. Strong book, "The Amateur Scientist." Check it out: http://www.vk2zay.net/article/222

Hey Alan, can you make us up some of those X-Ray glasses that they always advertised in the backs of magazines? As a teenager, I somehow always wanted one of those...

Class C Amps and the Load and Power Out Formulas

While up in Rotterdam I started thinking about Class C Amps and the standard formula used to calculate power out and load resistance: Rl=(Vcc-Ve)^2/2Po. I understand why this formula works for Class A amps: The Vcc-Ve term describes the maximum voltage you can get at the output. The rest of the formula is just a version of P=IE and P=E^2/R. The 2 in the denominator converts peak to average. The books tell us that this same formula applies to Class C amps. How could that be? I wondered. Doesn't the output of a Class C amp look (pre-filter) like a series of pulses at the operating freq? Wouldn't that require a somewhat different formula?
The answer came from SSDRA and LTSpice. SSDRA page 25 explains "If we assume that the collector voltage varies from zero to twice the Vcc level while delivering the desired output power, the load needed at the collector is given by the familiar relation Rl=Vcc^2/2Po." (Emphasis added.) The voltage at the collector is being pulled down nearly to zero as the voltage at the base goes positive and the transistor conducts. You can see this in the waveform in the LTSpice screenshot above. Then, when the input voltage dips below about .6 volts, the transistor goes into cutoff and stops conducting. At this point the energy stored in the inductor in collector circuit is dumped onto the collector, raising the voltage there to about twice Vcc. That the ugly spike you see at the top. Wow, you can really see from this the need for output filtering.
As I was exploring this issue, I cam across an old LTSpice VideoCast from December 2006. See below.
BTW: These are the kinds of questions explored in the book "SolderSmoke -- A Global Adventure in Radio Electronics." I'm hearing that delivery is very fast, especially in the UK.

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!