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Saturday, April 30, 2011

Working on T/R circuit for HB WSPR rig --need help!

I'm finally working on the PTT T/R circuit for my homebrew DSB /Direct conversion 30 meter transceiver. I hope to use the simple one transistor circuit from W3PM's FB HB WSPR rig.

But I need info on the PTT signal that will come from the computer serial port. Which pins on the 9 pin serial port connector? What kind of signal comes out? Is it 5 volts on transmit? What settings should I use in WSPR? RTS? Any other setting changes needed?

I hope to be transmitting AND receiving soon.

Friday, April 29, 2011

AMSAT OSCAR 7 -- No Batteries, Running Directly From Solar Panels

From the AMSAT site:

AMSAT-OSCAR 7 was launched November 15, 1974 by a Delta 2310 launcher from Vandenberg Air Force Base, Lompoc, California. AO-7 was launched piggyback with ITOS-G (NOAA 4) and the Spanish INTASAT. Built by a multi-national (German, Canadian, United States, and Australian) team of radio amateurs under the direction of AMSAT-NA. It carried Mode A (145.850-950 MHz uplink and 29.400-500 MHz downlink) and Mode B (432.180-120 MHz uplink and 145.920-980 MHz downlink (inverted)) linear transponders and 29.500 and 145.700 MHz beacons. The 2304.1 MHz was never turned on because of international treaty constraints.

In mid 1981 AO-7 ceased operation due to battery failures. It was thought at that time that the batteries had shorted. However on June 21, 2002, at least one of the shorted batteries went open-circuit, allowing the satellite to waken whenever it is in sunlight, and randomly begin operation in one of 4 modes.

According to the log at, this old warrior is still supporting transponder action in mode A and mode B as recently as 9/10/09, and on a regular basis, whenever it is in sunlight.

When the satellite is in sunlight for extended periods of time, the 24-hour timer still switches the bird between modes A and B. Listen for the corresponding beacon to determine which mode the satellite is currently operating in, or refer to the above mentioned web page to see what mode has recently supported QSO\'s as the best estimate of what is the current mode of operation.

Please remember, there are no (functional) batteries, so the satellite\'s power input is limited to whatever output can be generated by the ancient solar panels. Use the least uplink power possible to minimize your downlink power usage, and maximize the number of simultaneous QSO\'s supported in the passband. There are other operating tips at:
Linear transponder birds are a scarce commodity these days, so please use AO-7 responsibly, but please DO enjoy her!

Wednesday, April 27, 2011

50th Birthday of the Silicon Integrated Circuit

Robert Noyce got his IC patent on April 25, 1961.

Of course, wave soldering would be something to come out of California.

Tuesday, April 26, 2011

Free Kindle Reader for your PC

This link will take you to the download site. The software will allow you to use your PC as a Kindle reader.

Then be sure to get a copy of SolderSmoke -- The Book

Sunday, April 24, 2011

SolderSMOKE APRS symbol

I've been setting up my satellite APRS station. This weekend I finally got the UI-view software running. I had to pick an icon -- this would be the symbol that would show up on the mapping software. In the Azores I had a nice little island with a palm tree. Here in Virginia, well, as I scrolled through the options, suddenly I saw something that seemed appropriate. The coordinates are a bit off, but that, my friends, is a smoke stack emitting 60/40 fumes.

How to Join G-QRP (and get SPRAT) in the USA

From the G-QRP web site:

Formed in 1974, the GQRP Club is a non profit organisation run entirely by volunteers to promote Low Power Radio. Whether you have a ham licence or not - everyone is welcome. Our quarterly magazine SPRAT provides a fascinating read containing articles of varying complexity, from simple test equipment, to fully functioning radio transmitters and receivers. Membership fees are about as low as you will find anywhere and our club sales service to members is second to none.

Indeed. Joining G-QRP and getting SPRAT is something all QRPers and homebrewers should do!

Some SolderSmoke listeners have asked me how they can join G-QRP from the U.S. Bill Kelsey is the club's man in America:

Bill Kelsey - N8ET 3521 Spring Lake Dr., Findlay, OH 45840 U.S.A.

$18 paid in USA.

Bill's e-mail and more info here:

OR... You can pay directly via PAYPAL:

Saturday, April 23, 2011

Messages (for me!) from space station

When I started receiving packets via the International Space Station earlier this month, I noticed a familiar call: KB1GVR. He was one of the few North American stations who could pick up my packet beacons via PCSAT -- he would then relay them to the internet. This month, when I sent my sigs through the ISS, OM GVR spotted them, and sent reply messages to me via the packet system. I didn't get them via the satellite -- they came to me via the "Stations Heard Via ISS" web site. But still, it was fun to run into an old friend via the space station.

Friday, April 22, 2011

The Novice License: Two Years on PROBATION!

Somehow I remembered it as being one year, non-renewable, but Neil, WA4CHQ, wrote to tell me that he remembered a two year term. I think Neil is right. The excellent web page of the Novice Historical Society provides the details and many really nice stories from our days as novices.

Thursday, April 21, 2011

555 Contest Finale

Jeri Ellsworth's 555 contest is in the home stretch, and I've got my acceptance speech all ready. "I'd like to thank the members of the Academy... and above all the people of the Azores, who were put at risk by the large kite that carried my 555 timer circuit and 35 mm camera over their unprotected heads..."

Here's my entry:

Forrest Mims is one of the judges. Here is what he had to say:

[The participants] displayed an absolutely remarkable range of engineering skills, creativity and dedication to meet the deadline. Also impressive was the use of video and photography to illustrate many of the entries.

This contest helps restore my confidence in analog designers, who have become a very small minority in electronics these days. Some of these projects do with great simplicity and efficiency what exclusively digital designers would have great difficulty emulating. Moreover, a number of these projects have potential commercial merit. Hopefully the developers will be able to pursue this.

The winners will be announced tonight at 9 pm Eastern Time:

(Oh no! There must be some sort of mistake! I checked the list of finalists and my kite entry is not there!)

Wednesday, April 20, 2011

SolderSmoke Podcast #133

April 19, 2011

-- KindleSmoke
-- Amazon's Whispernet (not to be confused with WSPRnet)
-- April 1 and the Perils of Plausibility
-- The difference (significant!) between Cream of Tartar and Tartar Sauce
-- A short Italian lesson
-- Polyakov QRSS
-- Snort Rosin's Mighty Mite (NOTE: NO FILTER!)
-- Fly Fishing in Space: 2 Meter Packet Beacons and the International Space Station
-- Upside-down Amplifier
-- Rock and Roll and Ham Radio: The Bob Heil Story
-- The Shuttle Discovery Lands in Northern Virginia

Check out the new Ikea Microphone!

New HamStack Project Boards from Sierra Radio Systems

From Sierra Radio Systems (our sponsor):

We just got a batch of new boards that are a very handy companion to the HamStack CPU board. We call it a "Project Board". If you are embedding a CPU board into your own project, that works fine. However, if you want to build a stand-alone application, like a keyer, sequencer, DTMF decoder, reset timer, tone generator, whatever, you will need a power supply, connectors and some sub-circuits. That is what the project board includes. You plug the CPU board on top of the project board and you can program it to do all kinds of things.

The board includes the following sub-circuits...
- 2 digital inputs with 10 pullup resistors to +5v DC
- 4 analog inputs with a selectable voltage range of 0-5 or 0-22 volts DC
- 3 high speed, quiet, SPST reed relays capable of switching up to 500 ma.
- 1 opto isolated digital output
- 1 RS-232 serial port
- 1 analog signal output that can generate a sine wave 0-5kHz at 0-5v DC
- 8870 DTMF decoder chip
- 1 Temperature probe input
- 3 additional general purpose CPU IO connections
- 5v DC power supply (supply rail for logic and analog chips)
- 2.5v DC power supply (bias supply for op amps)
- 3.3v DC power supply (supply rail for 3.3v parts)
- 5 pole low pass filter to condition the analog signal generators output

For repeater builders, you can use the DTMF decoder and relays to make a master site reset controller that sits outside the repeater controller.
You can use the tone generation function to make a portable or bench top test tone generator.
You can use the reed relays to do timer based computer resetting.
Make a CW IDer or beacon transmitter controller.
Battery voltage monitor. Read the voltage, when low, one of the reed relays keys the repeater transmitter and the tone generator send a beep or CW message.
We are writing a really cool keyer app that will do iambic mode A/B, record and send programmable macros, with an LCD to show the speed and use a digital rotary encoder to set the speed.
The keyer will be open source and you can hack it to your hearts content.

Anyway, its the perfect platform to build a HamStack based ham radio project. The HamStack (and project board) supports programming in C or Basic.

Check it out on the web site


Monday, April 18, 2011

Don Norgaard, W2KUJ -- SSB Pioneer

In SolderSmoke -- Global Adventures in Wireless Electronics I tell of how I struggled to understand the inner workings of my Hallicraters HT-37 single sideband transmitter. This rig used the phasing method of sideband generation, and as a kid I just couldn't understand how it really worked. And this really bothered me. As I recount in the book, through a QST article that was reprinted in the ARRL book SSB for the Radio Amateur, Don Norgaard came to my rescue and allowed me to understand the phasing method.

It was only recently that -- through reading the August 1998 issue of an Electric Radio Magazine article by Jim Hanlon, W8KGI -- that I came to realize that Don was one of the true pioneers of SSB. I think this blog post may be one of the first presentations online of a picture of OM Norgaard. The 1951 QST article notes that "the face may be unfamiliar."

In addition to writing very clear QST articles, Don was the creator of a rig that "revolutionized amateur use of SSB." It was a three tube 75 meter SSB transmitter called the "SSB, Jr." From Jim Hanlon's article: "It used nothing more complicated than simple coils, condensers, resistors, one carrier frequency oscillator crystal, four germanium diodes and three tubes in the classic phasing circuit to put out 5 watts PEP."

Three cheers for Don Norgaard! Three cheers for the phasing method!

Sunday, April 17, 2011


Monday, April 4, 2011 11:27 AM

"solder smoke"

CREAM OF TARTAR - A fine white powder used in cooking. It is the potassium salt
Potassium bitartrate, KC4H5O6. It is a food stabilizer and is also used in some baking powders.

TARTAR SAUCE - A sauce for seafood made from mayonnaise, pickles, and onions. It is unrelated to cream of tartar.

73 de Steve WA0PWK

Italian Chemical Tailoring of Crystal Microphone Elements -- The Bugiardo Method

We will discuss this in SolderSmoke Podcast 133, but for those of you who are not among the MORE THAN 200 listeners who went to the recipe site, I thought I should post the REALLY INCREDIBLE e-mail that started all this.

Before you read it, you might want to fire up that Italian-English translation feature in Google and check out the meaning of some of names and places. Like Dr. Andrea BUGIARDO who wrote in the Italian magazine Radio-FURBIZIA while living in the beautiful mountain town of SCERZO-BARZELLETA in the picturesque (I'm sure!) province of TRUCO-IMBROGLIO.




Ciao Bill! Greetings from not-so-sunny Roma! After I read you blog posting ( with the video about how to grow your own piezo-electric crystals at home, I was reminded of an article from an old Italian radio magazine that I came across not long ago. Having heard of your recent (well, long-standing) problems with audio quality and microphones, it occurred to me that this old Italian article might be the solution to your audio difficulties.

The article appeared in the Italian radio magazine "Radio-Furbizia" April 1950. Tough times in Italy! Hams had to be inventive and ingenious, and they had to put to work whatever resources they had at hand. Dottore Andrea Bugiardo, I0SOL, was clearly a man for those times. During the post-war period, writing from his hamshack in the beautiful village of Scherzo-Barzelleta, in the province of Truccoimbroglio, OM Bugiardo produced a steady stream of truly incredible ham radio innovations.As you know, life in an Italian home revolves around the kitchen, so it should come as no surprise that Bugiardo based many of his devices on things that he found there.

Bugiardo opens his April 1950 article with a really touching admission of his deep, unfulfilled yearning for a Astatic D-104 microphone. I know this mic was not warmly received by your listeners (insensitive brutes!) but for Bugiardo, the D-104, with its chrome and its art-deco lines was the epitome of ham radio class! As you know, style and good design are important for Italians -- this is the country of "bella figura!" But alas, the dire economic situation did not permit Dr. Bugiardo to buy his coveted chrome lollipop. But, being a true ham, a ham's ham, he decided to "roll his own"as you Americans would say. He decided to build his own D-104.

The exterior did not represent a major problem. He had many friends in Milano who could handle the needed metal and chrome work. The problem was electrical... or should I say electro-mechanical. You see, Bugiardo needed the key component, or perhaps I should say, the key ingredient: he needed the piezoelectric element, the transducer, the piezo-electric device that transforms sound to electricity. It is very interesting. In growing his crystals, Bugiardo employed essentially the same techniques as described in the video on your blog. But -- and here is where I think his article could help you -- he went a significant step further and described how -- by using simple substances found in any kitchen -- the audio characteristics of the microphone can be tailored to the needs of any individual human voice. Bugiardo's research showed that by adding certain common crystalline substances to the standard mix for piezo-electric crystals (the familiar Tartar sauce formula) we can actually come up with the kind of mic we need! No need for EQ or mixer boards! Just start out with the right kind of crystal for your voice, and you are, as you guys say, "good to go!

The physics of this is all based on the physical mechanics of the crystals -- motional inductance and all that. I'll spare you the gory details. Here is the essential information:

-- You start with the standard mix for the crystal element as described in the ARRL Handbooks (this formula appears in all the handbooks from the 40's and 50's).

-- In order to have a mic that accentuates the high notes in the voice, add approximately 5 grams of sugar to the mix.

-- For a stronger bass response, highlighting the low frequencies, add approximately 5 grams of salt. Ordinary table salt will do.

-- For a "punchy" DX-hunter's sound, Bugiardo recommends adding some Tabasco sauce to the Tartar sauce before the initial mixing. (He says this will give you about 3.2456 db gain!)

-- As for your whistling SSSSS problem, Bugiardo's "cook book" does seem to hint at a solution: He says that by adding some molasses to the mixture, you can sort of "smooth out" the response. (This is no doubt caused by the molasses adding its sticky-ness to the crystal matrix.) PLEASE give this a try Bill. Mama Mia! Those whistles hurt my ears!

Anyway, I hope this proves useful. We all really enjoy the podcast.



Saturday, April 16, 2011

We're #1! (On Kindle) Free Kindle Reader

I'm happy to report that the Kindle edition of SolderSmoke -- Global Adventures in Wireless Electronics is proving to be wildly popular. For a while this week it was #1 in Amazon Kindle's
"Electronics" category, and #2 in "Radio and Wireless" (we were beat out by Thunderstruck by Erik Larson -- a book that I liked very much).

Here's the link:

It is a lot cheaper and easier to get this e-version of the book. And you don't even need a Kindle! If you go to the Amazon Kindle site, and go to the lower right, you will find links to download free software that will turn your PC, or Blackberry or other mobile device into a virtual Kindle.

One reader noted that the system used by Amazon to electronically distribute the books (over the cell phone systems) is called Whispernet. Not to be confused with our beloved WSPRnet QRSS QRPp system (the download would take a LONG time on WSPRnet!)

Here's the back cover blurb on the book:

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.”

Friday, April 15, 2011

Space Beacon Success (and failure)

On the Yuri Gagarin anniversary day, I listened for the FM voice beacon from the ARISS-1 satellite on the space shuttle. Nothing heard here. But I was listening near the end of the period scheduled for the transmission, so I may have missed it, or the batteries may have drained.

But this morning I finally got confirmation that at least one of my packets made it through the Space Station's digipeater. The image above is from the "Stations Heard via ISS" web site. Obviously I need to do something to the position (Lat/Long) info in my packet so that I can show up on the APRS maps. Perhaps my symbol should be the SolderSmoke logo...

Wednesday, April 13, 2011

Homebrew Two Dollar Oscilloscope

This is from a short article in the April 1997 issue of Electric Radio magazine. The author is Bob Dennison, W2HBE. Bob is a real genius, and the author of many inspirational articles in ER.

The Sundt Engineering Company of Chicago was advertising this kind of device in the June 1936 issue of Short Wave Craft Magazine. Only two dollars (but that was big money in 1936). From Bob's article: "When the transmitter is modulated with a single audio tone, the waveform of the modulated carrier will be seen. By varying the motor speed (horizontal scan rate) the pattern can be synchronized or made to stand still. Percentage modulation is readily estimated by simple inspection of the display."

So here we have the perfect minimalist 'scope to go with a minimalist AM transmitter!

Tuesday, April 12, 2011

EME, Bob Heil, and The Grateful Dead

I really loved the TWiT interview with Bob Heil that I posted yesterday. Today we bring you a truly "must see" video on the History of Heil Sound. Really great stuff. Now I know that it was FATE that caused it to be a Peter Frampton song (using a Heil Talk Box) that helped me solve my RFI problem.

Bob Heil seems a really great guy. I liked the bio that he has on his web site.

Name: Bob Heil
Bob Heil
Position: CEO/Founder
Started in: 1940
Bio: Bob's life mission is to have fun and bring LOTS of people along for the trip. Bob barely got through grade school and then started making more money than his teachers by playing the (Hammond) organ. Then Bob became a pimp for his high school gym teacher (Sarah can fill you in on the details). Bob had 50+ years of "just OK" life until God sent him a red headed bundle of joy along with her bundle of joy and together they have more fun than a couple of squirrels in a nut forest.

Monday, April 11, 2011

Interview with Bob Heil

W8FG alerted me to this interview with Bob Heil on TWiT. I think you guys will enjoy it (especially all of you rockers out there).

Sunday, April 10, 2011


FROM STEEL: The Making of a Soulcraft from michael evans on Vimeo.

We need videos like this featuring our kind of smoke!

Saturday, April 9, 2011

Beacons from Space! Yuri Gagarin Anniversary

ARLS005 ARISSat-1 On the Air for Gagarin Anniversary

Space Bulletin 005 ARLS005
From ARRL Headquarters
Newington, CT April 8, 2011
To all radio amateurs

ARLS005 ARISSat-1 On the Air for Gagarin Anniversary

To celebrate the 50th anniversary of the first human spaceflight by
cosmonaut Yuri Gagarin, the ARISSat-1 satellite aboard the
International Space Station will be on the air using the station's
external antenna. Transmissions will begin on Monday, April 11, at
14:30 UTC and continue until 10:30 UTC on April 13.

To preserve the satellite's battery, transmissions will cycle on and
off. ARISSat-1 will transmit for 40 to 60 seconds, and then remain
silent for 2 minutes.

The FM transmissions on 145.950 MHz will alternate between a voice
ID, telemetry values, SSTV images and audio greetings in 15
different languages. One of the transmissions will contain audio of
a conversation between Gagarin and ground controllers that was
recorded during the historic flight.

A CW beacon will be heard on 145.919 MHz cycling between the
ARISSat-1 call sign, telemetry and call signs of individuals
involved in the ARISS program.

BPSK-1000 telemetry transmissions will also take place on 145.920
MHz SSB using the new 1kBPSK protocol developed by Phil Karn, KA9Q.

AMSAT will issue commemorative certificates to listeners who receive
the ARISSat-1 transmissions. Reports can be e-mailed to or Include your name, call
sign, a description of what you heard and the UTC time you heard it.
Recording the battery voltage telemetry values and the UTC time you
received them will be especially helpful.

You can determine when the International Space Station will be
passing overhead by using the AMSAT-NA online pass prediction tool

Another QRPoet

I'm a big fan of Ade Weiss, and I often find myself reaching to his "History of QRP" for technical or techno-literary inspiration. Most writing about ham radio is (understandably) done in a very straightforward technical way, without a lot of emotion. But Ade's writing style captures both the technical and the emotional aspects of homebrewing and QRP. There is a definite poetic elements to it. This article was sent to us from the Hobbit Hole by the Poet Laureate of QRP (AA1TJ). Just click on on the image to enlarge. From a 1973 issue of The Milliwatt:

Friday, April 8, 2011

How cool: HOWTOONS!

That's the spirit! Maker blog led me to this very nice tech cartoon site aimed at bringing kids into the world of making things:

Thursday, April 7, 2011


OK guys, please reach back into your memories, back to the late 80's, back to those sad days before the internet, back to the days of TNCs and packet BBSs and all that. I need some help.

I have my little 2 meter packet station running. I'm sending out beacon packets on 145.825 MHz, the freq of the International Space Station. (Is PC-SAT still on that freq also?)

Every morning I go to the old 1994 Satellite Pro computer (thanks to ZL3KE!) and type in mheard to see the list of stations picked up during the most recent passes of the space station. Every day there are several, each with an asterisk indicating that the packets were digipeated, and on this freq the digipeating is done in space.

Here's my question: Two days ago, MY OWN CALLSIGN showed up in the MHEARD list. (Cue ominous music) BUT WITHOUT THE ASTERISK! If I had seen the asterisk, I would have thought that my own packets were being digipeated by the ISS station and coming back at me. But why no asterisk? Long Delayed Echo? Klingons? My misunderstanding of packet technology?

Wednesday, April 6, 2011

SolderSmoke Book -- Now on Kindle!

In response to popular demand, "SolderSmoke -- Global Adventures in Wireless Electronics" is now available as an e-book for Amazon's Kindle.

Here's the U.S. site:

And here's the UK site:

Tuesday, April 5, 2011

Inside the SolderSmoke Microphone

Here's a really excellent description of how an electret microphone works, complete with a dissection of the device.

Crystal mics are much more interesting, of course, because of the opportunity to chemically tailor the audio response...

Monday, April 4, 2011

The Polyakov QRSS Receiver

Of course, we like it because it is in an Altoid-like box. And because it is Direct Conversion. And because it is used for QRSS, with the output fed to an on-line grabber. But this one is EVEN BETTER because it uses a Polyakov detector!

Check out PA1GSJ's receiver:

View the output (live):

More on Polyakov detectors:

Sunday, April 3, 2011

Snort Rosin's Mighty Mite: The Super Duper X Spy Transmitter

Hi Bill,

Attached is a picture of the remains of my transmitter, "The Super Duper X Spy Transmitter". My little rig didn't sit around; it made QSOs the day it was finished, 41 years ago. Since then it has bounced around in various junk boxes and had some parts robbed for other projects but thankfully it's still mostly intact.

I constructed it based upon the original article in Ed Noll's book, "Solid State QRP Projects", pg. 51, Project 17, "10 160 All-Band Two Watter". That transmitter was later to become known as the Michigan Mighty Mite.

My MMM (or SDXST if you will), features a built-in relative power detector, a microswitch key (upper right-hand corner), room for an internal 9 Volt battery and a jack for external power. The jacks are each different; a BNC for the antenna, a 3.5 mm closed-circuit jack for the key, a 2.5 mm for the relative output meter and a phono jack for the external power. My notes say that I added a .1 uF Emitter bypass and that it increased the power output by 50%. I also used a toroid for the output tank instead of the 1-3/4" coil form called for in the article. Use of the "Sucrets" box was not my idea; I got it from one of the ham mag's. of the day, probably 73.

Your coverage of those little rigs has motivated me to restore mine and make some QSOs for old times sake. With, of course, the proper output filter :-). I'll send a picture of the 'guts' when it's finished.

73.......Steve Smith WB6TNL
Thanks Steve. Great stuff. But... WHERE'S THE OUTPUT FILTER?

Saturday, April 2, 2011

Lulu Book Sale (20 % off) extended through April 4

Just use the Coupon Code SPLISH at checkout -- save 20% through April 4.

Friday, April 1, 2011

More on Chemically Tailored Crystal Mic Elements

My mention in SolderSmoke # 132 of this technique to custom tailor the AF response of crystal mic elements has already generated a lot of interest. Here's the e-mail from Italy that alerted me to the work of Dr. Andrea Bugiardo:

Check it out!
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column