Monthly Archives: November 2014

Interesting Ideas: Two-way Optoisolator made with two LEDs

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When I was but a wee lad around the age of 10, I wandered into a Radio Shack with my father.   Of course, this is back when Radio Shack sold good electronics parts.  I wanted to know what they did.  My dad didn’t know.  Somehow I ended up with a copy of Getting Started in Electronics by Forrest Mims III.  The book was handwritten and the illustrations were hand drawn, and it was perfect for kids.  Or adults.  I still have a copy of this book, not the original one my dad bought me — I’ve since lent that out many years ago.  But I was able to pick up a copy from the third printing, still with the original green cover, and I’ll hold on to that one forever.  It cost something like three bucks at the time.  The book is still in print — you can get it from Amazon, Jameco, or from the W5YI group.

Homemade optoisolator made with two LEDs (drawing by Forrest Mims III)

I found this article at Jameco.com that Forrest wrote about using two LEDs as an optoisolator by mounting them facing each other and wrapping them in electrical tape.  I would probably use heat shrink tubing if I tried this.  This is an excellent application showing that an LED can also be used to detect light.  The example circuit uses the homemade optoisolator feeding a 4011 CMOS NAND gate as a driver for an output LED.

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Hams and the Law: FCC revokes KB7ILD, finds sex offender ineligible to hold radio license.

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The ARRL reports that the FCC has reversed a previous determination by an Administrative Law Judge that had allowed David Titus KB7ILD of Seattle to renew his license in 2009 in the wake of a sex offense conviction.  From the ARRL article:

“We find that the ALJ erred in holding that the Enforcement Bureau failed to meet its burden of demonstrating that Titus is currently unqualified to remain a Commission licensee,” the Decision said, “inasmuch as the ALJ failed to consider relevant convictions for sex offenses and failed to give appropriate deference to the judgment of local law enforcement authorities that Titus is a convicted sex offender who poses a high risk to the safety of the community.”

In January 2007 the FCC issued a show-cause Order and designated for hearing the issue of whether Titus was qualified to remain a licensee in light of a 1993 felony conviction for “communicating with a minor for immoral purposes.” The Communications Act provides that the FCC may revoke any license, if conditions come to its attention that would have warranted a denial of the licensee’s original application. The Commission has said in the past that felony convictions, “especially those involving sexual offenses involving children,” raise questions regarding a licensee’s character qualifications.

Titus’s General class license expired in 2009, and the FCC had deferred action on his renewal application while the revocation proceeding was still in play. The FCC also dismissed Titus’s 2010 reply to the Enforcement Bureau’s exceptions in the matter, because they were filed 5 days late. The FCC said Sippel should have given more weight to incidents in 2002 and 2004 that, while not resulting in conviction, “prompted the Seattle Police Department to raise Titus’s assessed risk level from moderate to high.”

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Ham TV: W5KUB webcast with “Arduino and Ham Radio” author Glen Popeil KW5GP

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Tom Medlin W5KUB is probably best known for the many years of his live web broadcasts from the Dayton Hamvention where those unfortunately unable to make it to Mecca Hara Arena in Dayton each May could watch the Hamvention from their own home.  Tom and his crew lately have been branching out to cover other special Amateur Radio events such as the K6H special event station on the set of Last Man Standing in Hollywood in September.  Now Tom has created his own special event — an interview with Glen Popeil KW5GP, author of the new book “Arduino for Ham Radio” published by the ARRL.  I did miss the live broadcast — but Tom has put the video up on his archive page.  I’m kind of skimming through the video segments looking for the “good” parts. Oh – and special guest John Amodeo NN6JA, producer of ABC’s “Last Man Standing” makes a special appearance too.

I will probably pick up a copy of Glen’s new book, and I am hoping that it was much better prepared than the last ARRL-published microcontroller book that I purchased (“PIC Programming for Beginners“) which was published prematurely, poorly edited, and some of the PIC programmer parts were not even available by the time it was published. I’m serious, it was an unmitigated disaster–click here to visit the Amazon page and scroll down to the reviews.  This one was my review.  I met the author of that book the next year in Dayton and found out that he was as disappointed in it as I was and that there were publishing and marketing snafus.  Anyway, I’m willing to give the new Arduino book a chance.  The book is available direct from the ARRL or Amazon or probably your favorite book seller.

 

(published from DFW, Texas)

Crosstown Traffic: Hackaday features Raspberry Pi-powered foxhunt transmitter — with or without an actual transmitter!

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(my apologies about not posting in awhile.  I was on jury duty.  It was an emotionally draining case.  I’ll make up for it over the next few days.)

Hackaday ran an article yesterday that featured a hackaday.io project that Corey KM4EFP posted describing his Raspberry Pi powered Foxhunt transmitter.  What I found unique about this is that you can either feed the audio from a Pi output pin directly into a handheld transmitter, or actually transmit RF directly from the output pin (!) by adding a low-pass transmitter.  There is far more information about this project available on Corey’s GitHub page.  From the Hackaday.io project page:

My foxbox consists of a Raspberry Pi model B with Raspbian running pifox and is powered by a 6000mah usb power bank with a mausberrycircuits.com power switch and my gpio setup is laid out on an electro-resales gpio breakout pcb. All this is fitted inside a 30 caliber ammo can by use of non conductive foam padding. It starts transmitting automatically when the Pi is powered on and the transmit switch is flipped on. The transmission of my call sign and fox message and current time runs through gpio 4 and a lpf before reaching the antenna and also lighting an led indicating a transmission is in progress. No handheld is needed the Pi is the radio transmitter. You can also use audio out on the Pi to trigger vox on a handheld radio if your not comfortable building a low pass filter. Led and switches are also optional as well as automatic or manual transmissions and timing. Build your fox the way that suits you. There are many customizeable settings for pifox to fit your needs

 

We’ve seen directly driving an antenna from a GPIO pin before using PiFM.  I’m not sure I’d use it in any application where I would require frequency stability or any kind of a solid RF signal… but maybe the application of this is better than I originally thought.

 

(Published from DFW, Texas)

In the News: Ham radio operator featured in Bermuda newspaper for service during Hurricane Gonzalo

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John Stevens VP9NI, an amateur radio operator in Hamilton, Bermuda (where my wife was born!), was featured in The Royal Gazette (a Bermudian newspaper) for his service during Hurricane Gonzalo last month:

Canadian-born Bermuda resident John Stevens was the first to confirm to the NHC that Gonzalo had made landfall on the Island and his work was later credited by the centre.

His report, which included barometric pressure observations, made the 9pm AST Tropical Cyclone Update just after Gonzalo hit, and he continued to send regular reports after the storm had passed. As well as anecdotal information such as rainfall and wind direction, Mr Stevens was able to confirm to the NHC when the winds first reached hurricane force. He also told them when the eye of the storm landed and passed, and continued to deliver hourly check-ins. While Mr Stevens was not credited by name, there was an NHC report that credited a “Bermuda Amateur Radio operator with providing valuable information”.

Mr Stevens told The Royal Gazette: “When I got the confirmation I’d been mentioned in at least one of the updates from the National Hurricane Centre, I thought it was pretty cool. I thought I’d made a decent contribution despite having no [Belco (commercial)] power. There’s a bit of satisfaction and sense of accomplishment, I’d say.”

Also mentioned in the article were Craig Nikolai VP9NL of St. George’s Parish, Glen Cuoco VP9ID of St. George’s Parish, and Ed Kelly VP9GE of Hamilton, for their service during the hurricane.

 

(Published from DFW, Texas)

Ham Radio History: The Vibroplex Morse Code key and Carpal Tunnel syndrome in the late 1800s

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Vibroplex “Original Bug” model (picture from Wikimedia Commons)

On Saturdays, I try to visit the weekly Hams and Eggs gathering in Carrollton (please come and join us every Saturday from about 8 AM to 10:30 AM at the Whataburger off the Prresident George Bush Turnpike at the Old Denton exit).  This morning my friend Kevin N5KRG brought in an antique Vibroplex Morse code key and was mentioning a book he had read about this key which has been in continuous production for over 100 years.   The key was developed to help telegraphers avoid “Telegrapher’s Paralysis” or “Glass Arm” syndrome – today we call it “Carpal Tunnel Syndrome.” From a 1997 website titled the Telephraph Office: by Neal McEwen K5RW (from here in the DFW area-I wonder if I’ve met him).

Telegraphers, making the up and down motion on their keys all day, were often the victim of an occupational hazard related to the muscles of the wrist and forearm. Today we call this malady “carpal tunnel syndrome.” In the 19th century it was called “telegrapher’s paralysis” or “glass arm.” To alleviate some of the stress, the “semi-automatic” key was invented at the turn of the century. Today we are more familiar with the name “bug” to describe the semi-automatic key. The “bug” has a lever such that when pushed to one side, the operator can make a dash similar in manner to making a dash on the older style key. When the lever is pushed in the opposite direction, the “bug” makes dots in rapid succession until the operator releases the lever. This action, besides being in the horizontal plane rather than the vertical plan, has reduced significantly, the required manipulation to form the characters of the code.

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