Date: Feb. 5, 1999

Jon Hagen Wrote: Dear Frank, I really enjoyed "Back in the Day's of Radio". But wasn't that a 6AG7 rather than a 6SJ7 in the Heathkit transmitter? Jon Hagen jonhagen@naic.edu

Frank's Response John, I am not sure. I tried to look in my ARRL Handbook and found it had been sent to the circular file many years ago. I wonder if anyone knows what the oscillator tube was in the Heathkit AT1 amateur radio transmitter. Was it a 6SJ7 or a 6AG7? I think John is right.

Frank,

Quick searches of Advanced Book Exchange (http://www.abebooks.com/) and Add All (http://www.addall.com/) show a bunch of bookstores that have used or remainder copies of Tom Lewis's Empire of the Air. BookCloseOuts.com has the best price, $6.99 for the Harper Collins paperback, of which they have multiple copies.

John Barnes Advisory
Engineer
Lexmark International
jrbarnes@lexmark.com

2 items: my grandfather gave me both a mounted (3/8" metal tub) and an unmounted galena crystal years ago, that he said he used for a cat's hair radio. I tried the mounted one and it worked - the longer the antenna, th better.

Second, I recently watched the Empire of the Air video on the DeForest/Armstrong/ Sarnoff trio biography - available at my local public library...

John Linstrom
Computer Dynamics
john@cdynamics.com

Frank,

I appreciate the followup article to the original crystal set info. The links to other sites were the best part. I am also a HAM, thanks to two neighbors (both HAMS). I am in electronics thanks to a neighbor (a HAM) and my father (who was once so he could fly R/C planes). My dad and I built a crystal set when I was in elementary school. I got both the Electronics and Computer merit badges as a Boy Scout (not Radio, darn it). I tried all through high school to get my amateur radio license. I finally succeeded at that last hurdle in my Senior year of university studies toward an EE degree. I dabble in radio, and these days that means ANALOG and DIGITAL electronics, and computers (both PC for radio design and DSP in the radios), and antennas/electromagnetics. Many work assignments have been easier since I have the radio backgound, even though they do not have radio in them. If it weren't for the exposure to radio and electronics when I was young, I probably would not be writing this note to you!

Douglas L Datwyler
Sr. Hardware Engineer
datwyler@altatech.com

Frank,

About 1959, I got interested in radio, and built a crystal set from plans that were in Popular Science (as I recall). I made the crystal by heating lead shavings and sulfur (outside, of course) in a plumber's crucible with a blowtorch, then pouring the mix into a copper tube plugged at one end with sand. I cut the tube open and got my slug of material. Then I used a cold chisel and hammer to fracture it, and this became the active face of the crystal. A sewing needle was the cat whisker. Sometimes it even worked.

J. C. Kelly

Scott Deuty wrote:

In your article you indicate that the emphasis on computers and integrated circuits may have taken away the experiences of the radio days. I would like to give my son the best information and hands on exposure that I can. I hang out with a HAM here at work and have gotten some good input from him and forwarded your article to him. Still, if you have any suggestions about getting my son started, I would be glad to hear them.

David Zimmerman wrote:

I am always struck by how different things were then and now regarding how people get interested in this field. It was so obvious then to see our trail of interests; radio, communication, building things, design. How do people get interested these days in electronics when there are no kits, and most of the components are "systems on a chip"?

Larry Pizzella also wrote: (providing answers and more to the above questions)

Hi Frank,

I enjoyed your article about early radio. Thanks for writing it. You have probably gotten several emails on this but just in case. I would like to tell you that there has been a resurgence in Xtal radios. I think the Web has had a lot to do with it. I had a latent interest in Xtal sets since I was a kid, but it took my surfing the Web, and locating one site in particular, "The Crystal Set Society" to get me going again. (http://www.midnightscience.com

I urge you to check this site and at least one more. http://www.thebest.net/wuggy

Crystal Set Resources, that is run by Owen Pool, a High school Physics teacher and 30 year career (retired) Navy Officer. I think you will find them most interesting. There are many others, and Owen has done a good job identifying them on his links page.

I too noticed the code tone on the Titanic Radio was not raspy, like spark, but I was very impressed at the set. It looked very authentic to me. I wished it would have appeared more prominently, and a little longer. I also would like to note a minor correction about the mineral used in your XTAL radio. It was not Germanium, but Galena. Germanium is a refined element. Galena is Lead Sulfide, the ore from which Lead is refined. It turns out that one of the impurities in this soft crystalline ore is Germanium. I believe that these are the spots you search for with the Cats Whisker. Galena is a prime source of Germanium. Some deposits of Galena also have a high Silver content. Galena is a secondary source of silver. The concentrations of both Silver and Germanium is a very small fraction of a percent, but where you find significant amounts of silver, you also find significant amounts of germanium.

Many other minerals were found to make suitable detectors. In fact Pickard cataloged over 100. Some of the better ones (besides Galena) are Iron Pyrite, Chalcopyrite, and Bornite. A very popular detector was Carborumdum because a heavy pressure on the mineral worked best, and so it was not easily jarred off a sensitive spot. But it was not as sensitive as Galena, and needed a small dc bias current.

Most people do not realize that it was the early work with crystals and Cats Whiskers, that led to development of effective detectors for RADAR in WWII, and later to the search for an amplifying crystal at Bell Labs. A great popular account of this is described in the book "Crystal Fire" by Hodsen and Rierden (sp?). It is available through Amazon, or any good bookstore. This book also goes on to describe the development of the IC and how Silicon Valley got its start.

Please check out the web sites, and watch out, --it might arouse a latent interest and get you hooked. If it does you are in good company.

Sincerely Yours,
Larry Pizzella

My thanks to all who responded to this article. The Crystal Set information on the web sites that Larry mentioned looks very interesting. If anyone knows of other sources of kits and books please let me know and we will keep all informed.

Other websites that have kits are listed below. There is a surprising amount of them and many have "Radio" kits.

http://www.shopsite.com/kits/aisle28.html
http://www.elexp.com/kit_2srk.htm
http://www.hamsupplies.com/vect/kits.htm
http://www.altinet.net/softlink/ckits/index.htm http://www.rainbowkits.com/
http://www.electronickits.com/kit/complete/meas/ck102.htm

Frank Greenhalgh

About the Author

Frank Greenhalgh has been working in power supplies and systems for 38 years. He has many impressive accomplishments and patents. Over the years he has made significant contributions to Trio Laboratories where he held the position of Chief Design Engineer and was then promoted to Vice President.