You are probably familiar with the Ground Fault Circuit Interrupter (GFCI), also called Ground Fault Interrupter (GFI), Residual-Current Device (RCD) and a few other names. While doing some electrical work for a family member, I discovered Arc Fault Circuit Interrupters (AFCIs) in the breaker box. Having a genuine Electrical Engineering degree (two, actually), I’d like to believe that I am reasonably up to date on basic house wiring. But somehow AFCIs had escaped my attention, even though they started appearing in the National Electric Code over 10 years ago.

A bit of searching on the internet revealed that these newfangled devices are intended to detect arc faults are below the trip level of a normal circuit breaker. Think in terms of a frayed extension cord that arcs over, creating a fire hazard, but not exceeding the 15 ampere rating of a typical house circuit. As usual, the Wikipedia entry is a good place to start. AFCIs detect arcs by monitoring the current behavior throughout the 60 Hz cycle. There are characteristics in the waveform that indicate an arc condition exists, causing the AFCI to disconnect the circuit. This article goes into more technical detail if you are interested:

New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)

Just like GFIs, AFCIs are available for installation in the main breaker panel and for installation at the electrical outlet. The diagram below shows the block diagram of a typical single-phase AFCI. This is not your old school circuit breaker but a complex system that performs both arc and ground fault detection. As already mentioned, the arc detection is performed by sensing the current behavior. The ground fault detection senses the difference between the current leaving and returning to the device. If there is a significant mismatch between the two currents, a ground fault has occurred.

This post is just a quick introduction to AFCIs, with a USA perspective. Your local building codes are now or will soon be requiring AFCIs on new construction, so you’ll probably encounter them sooner or later. The National Electrical Manufacturers Association has a website with additional information: www.afcisafety.org.

73, Bob K0NR

The post Meet the Arc Fault Circuit Interrupter appeared first on The KØNR Radio Site.

Bob Witte, KØNR, is a regular contributor to AmateurRadio.com and writes from Colorado, USA. Contact him at [email protected].

I think the wind gods were against me on this day. I recently had a lovely evening with a few newly licensed amateurs, who asked a very simple question. How do you erect a radio mast for when you are on your own. Its something i never asked, and it was something i have perfected over a number of years.

So armed with the Go-Pro and log camera I visited my local park to try and demonstrate exactly how i erect the mast.

Of course, I never realised how windy it was, but i preserved and managed to record a quick video showing how i “get it up”

I hope the video is of use to you, and apologies about the audio.

Dan Trudgian, MØTGN, is a regular contributor to AmateurRadio.com and writes from Wiltshire, England. He's a radio nut, IT guru, general good guy and an all round good egg. Contact him him here.

I think the wind gods were against me on this day. I recently had a lovely evening with a few newly licensed amateurs, who asked a very simple question. How do you erect a radio mast for when you are on your own. Its something i never asked, and it was something i have perfected over a number of years.

So armed with the Go-Pro and log camera I visited my local park to try and demonstrate exactly how i erect the mast.

Of course, I never realised how windy it was, but i preserved and managed to record a quick video showing how i “get it up”

I hope the video is of use to you, and apologies about the audio.

Dan Trudgian, MØTGN, is a regular contributor to AmateurRadio.com and writes from Wiltshire, England. He's a radio nut, IT guru, general good guy and an all round good egg. Contact him him here.

Amateur Radio Weekly is curated by Cale Mooth K4HCK. Sign up free to receive ham radio's most relevant news, projects, technology and events by e-mail each week at http://www.hamweekly.com.

Facebook is throwing up memories from 3 years ago and one of these was a schematic for my WSPR RX for 10m, using low cost 14.060MHz crystals with a Polyakov mixer (injection at half signal frequency) The circuit worked well and could also be used for PSK31. Essentially this is a direct conversion receiver, but it mattered not. Even if you bought all parts new it is very inexpensive.  3 years later I would replace the 2 diodes by Schottky ones as these are now low cost and need less injection than the silicon ones shown.

Roger Lapthorn, G3XBM, is a regular contributor to AmateurRadio.com and writes from Cambridge, England.

So, a couple of days ago there was a bit of a flap over on Reddit.

A club called FBOM International which specializes in digital modes created a ham radio promotional video (embedded above) and it was posted (and stickied) to the /r/AmateurRadio subreddit.

Then came a reply from Yvette Cendes, KB3HTS, a student at the University of Amsterdam working on a Ph.D in Astronomy. Here is a portion of her post:

…Let me explain why I find it offensive that this video is now being touted as the ad for our subreddit: it objectifies women and relies on gender stereotypes that would make no woman feel welcome here. We are currently dealing with a hobby that is only 15% women that keeps fretting about getting more people involved in it, so why do we allow things that would drive half the population away? I don’t pretend to have all the answers on a complex issue, but I do know this stickied post is far from what we should want to represent the community. And it goes to show that if we ever have a crack at attracting more women into this hobby we have a long way to go.

I believe the folks who made this video did so with good intentions and without any ill intent whatsoever. In fact, I’m glad they posted it — because it gave Yvette a chance to show that what seemed perfectly fine to some people can offend others looking at it from a different perspective.

Her reply gives us the opportunity to think about why we’re not attracting more women to ham radio and to STEM (science, technology, engineering and math) fields in general. This is a big deal and regardless of whether you agree with her position or feel she overreacted, it’s a discussion worth having.

I’m middle-aged and male. If we’re trying to attract more old guys like me to this hobby, then maybe we can just keep on doing what we’re doing. But if we hope to add more folks outside of this demographic, then we may need to rethink our promotional strategy a little bit.

What are your thoughts?

Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].

courtesy: http://sdo.gsfc.nasa.gov/

Conditions on LF have been rather dismal for the past week and a half. Here in western Canada as well as most regions running along the southern edge of the auroral zone, the nightly visible auroras have been wreaking havoc on normal LF propagation as well as dampening HF during the day but ...





... the sun has been deathly quiet, as can be seen in yesterday's solar disk image.

It seems that just the 'normal' solar wind can disrupt things all on its own, without any solar flares or coronal mass ejections. In the late 70's, 'cracks' in the earth's magnetosphere were first observed... cracks that allowed even a quiet solar wind to actively interact with the earth's (normally protected) upper atmosphere. Apparently this is the present condition that has been disrupting normal propagation for the past many days.

The spaceweather.com web site has a nice explanation of how these cracks allow the Sun's Interplanetary Magnetic Field (IMF) to interact with the earth's field:

"Earth has a magnetic field, too. It forms a bubble around our planet called the magnetosphere, which deflects solar wind gusts. (Mars, which does not have a protective magnetosphere, has lost much of its atmosphere as a result of solar wind erosion.) Earth's magnetic field and the IMF come into contact at the magnetopause: a place where the magnetosphere meets the solar wind. Earth's magnetic field points north at the magnetopause. If the IMF points south -- a condition scientists call "southward Bz" -- then the IMF can partially cancel Earth's magnetic field at the point of contact.

When Bz is south, that is, opposite Earth's magnetic field, the two fields link up," explains Christopher Russell, a Professor of Geophysics and Space Physics at UCLA. "You can then follow a field line from Earth directly into the solar wind" -- or from the solar wind to Earth. South-pointing Bz's open a door through which energy from the solar wind can reach Earth's atmosphere!"

Earth's Bz has been pointing south during this entire period of poor propagation. Heavy ionization of the daylight D-layer, normally an 'absorber' of LF signals, has allowed reception of several NDB signals normally only heard at night. In fact, one of my favorite NDB propagation indicators, 25-watt YLJ in Meadow Lake, Saskatchewan, has been heard all day long on 406KHz for the past week as its signal skirts along the underside of the dense D-layer. These auroral conditions however, often enhance the path to the south Pacific and several western BCB DXers have reported excellent propagation to Australia and New Zealand in the pre-dawn hours.

Another indicator of LF propagation disturbance is the DST or Disturbance Storm Time index. This number gives an indication of the severity of the weakness in the magnetosphere, with numbers going further and further negative as the charged particles trapped in the magnetosphere increase in numbers.

courtesy:http://wdc.kugi.kyoto-u.ac.jp/dst_realtime/presentmonth/index.html

The DST has been having a rough ride since the beginning of the month and as these numbers grow more positive and remain there, propagation will return to normal. With late September and October often being among the best months of the year for LF propagation, and with the sun now doing its part by remaining quiet, let's hope that the earth's magnetosphere will also co-operate and seal-up those propagation-killing cracks.
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].