Five. Two. Seven. Six. Three. Six. Nine. Eight......

Nick, KB1SNG, reports that he was brought into ham radio via an interest in the infamous "Numbers Stations." He sent along a link to a very interesting site on this subject:
http://www.simonmason.karoo.net/page30.html

Italian Experimental Station in the Good Old Days... And Today!

Today (he tells me it is 50 years later!) my friend Gianfranco is on the air as I0ZY.
Transmitter back then was homebrew except for a Geloso VFO purchased for 7000 lira (11 dollars at the time). Tubes were 6J5's and 6V6's. It ran AM. Two 807's in the final with 600 volts on the plates. Two 6L6's running AB2 as the modulator. His mic was salvaged from an old wire recorder. Except for the VFO, everything was from WWII surplus.
On the receive side, he had an HRO 5 by National that he picked pretty much in the same flea market area that we visit today. It was in such bad shape that they gave it to him for free! With a lot of patience and persistence, he was able to get it to work on 20 meters. Gianfranco clearly had The Knack!

And he still does! He now has a wonderful company (SPE) that manufactures in Italy some very advanced linear amplifiers. He is the designer and creator of the Expert 1K-FA. Check out this video on his company and his product:



Here is the link to the site for the Expert 1K-FA:
http://www.radio-ham.eu/Expert1K-FA.htm

SSSSSSolder SSSSSSSmoke's SSSSSSS problem

In SolderSmoke 109, I did a little experiment. Normally I do some audio processing using Audacity's Equalization option. In all of the recent episodes, I have been using an equalization curve similar to the one shown above. I drop off the low frequencies (to get rid of the Popping P sounds) and I put a notch at around 3500 Hz in an effort to get rid of the problematic SSS sounds. I had my doubts about the effectiveness of all this. Partly in an effort to save time, SolderSmoke 109 I dispensed with the processing. I immediately got a couple of e-mailed signal reports saying that the nasty SSSS sound was back.
I really can't hear it on my computer. This may be related to different sound cards. And some high frequency hearing loss that I picked up on the rifle range may be involved.
If you can, please compare the sound quality in SS108 with that of SS109, and let me know what you think.
Dean, WA6P, and Bill W7AAZ, going to send me a passive audio filter that we hope will help.
On a similar note (!), I am looking for a circuit for a simple audio signal processor for use with my DSB rigs. I need something simple that will provide both clipping (probably via the standard two diode arrangement) AND audio frequency selection. The ability to put upper and lower limits on the audio frequencies is important in DSB rigs, because they lack the crystal filters that do most of this work in SSB transmitters.

SolderSmoke -- The Book. Table of Contents

As promised in SolderSmoke 109, here is the Table of Contents for the new SolderSmoke book.

CONTENTS

Preface

Chapter 1 Electrically Inclined – Tales of an Electromagnetic Youth
Electrons and Electricity
Radio Waves
Some Basic Equations
Einstein in the Transformer
Semiconductors

Chapter 2 Off-the-Air—Amateur Radio Goes Into Hibernation
Junctions and Diodes

Chapter 3 Tropical Rebirth—Ham Radio in the Dominican Republic
The Lowly Capacitor
Resonance and Oscillation
Series and Parallel Tuned Circuits

Chapter 4 Boatanchors in Virginia—Back in the U.S.A.
Transistor Amplifiers
Mixers
Modulation: AM, DSB, SSB

Chapter 5 Mid-Atlantic Outpost—Amateur Radio from the Azores
Balanced Modulators

Chapter 6 Urban Radio—Solder Smoke in Central London
Amplifier Loads

Chapter 7 Rome—Secret Radio in the Eternal City
Feedback in Amplifiers

Chapter 8 Conclusions—A Brotherhood Without Borders

Acknowledgements

Index

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

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