Aircraft headset to ham radio adapter

Aircraft headphone adapter mounted to ham radio Catching up on long-overdue blog posts, here’s a project I did a couple of years ago to adapt an aircraft headset to my Yaesu FT-857D ham radio. Aircraft headphones are optimized for the high-noise environment of an airplane—the earmuffs keep the ambient sound (noise) out and the microphone is designed to let only the pilot’s voice in. While I haven’t used my ham radio in a plane, the headset works well in other noisy environments.

OK, but why an adapter?

A little history

Aircraft communication systems had their formative years in the 1930s and 1940s; so much of the communication technology used in today’s aircraft was designed to meet technical requirements established back in the ’30s.

For this project, the microphone technology standards are what drive the requirements. The electrical standard for aircraft microphones is based on the carbon microphones used back in the formative years. Besides being available in the 1930s, carbon mikes are naturally noise cancelling and work well in an airplane. They also need some electrical current to work. This adapter provides the current necessary to make an airplane-compatible microphone work with a ham radio and it adapts the connectors–the headset’s connectors are also not compatible with those used by the ham radio.

The project

The design project was more mechanical than electrical. The headphones (speakers) on the headset are electrically compatible, so only a connector adapter is necessary. The electrical circuit used is a composite of several I found on the web and in QST, the magazine of the ARRL, and requires only a few components. Nevertheless, the hard work was in getting it all to fit in a box. Unlike my timer project, looks and durability were important design criteria.

Some of the requirements:

The high-order bit: it had to adapt an aircraft headset to the ham radio.
The adapter case had to support the stiff headset connectors.
The case had to be as small as possible, but large enough for all the connections and cables.
The cables and connectors had to survive multiple connections and disconnections.
The case had to be removable but, when mounted to the radio, mounted securely.

The results

The end result came out rather well and has survived two years of domestic and overseas deployments. With any luck, it’ll survive as long as the timer project I described a while back.

HeadsetAdapterBox contains the mechanical drawings, circuit schematics, and parts list, if you’re interested in building one. (Some assembly required–actually, ALL assembly is required!)

The inner workings of the finished adapter

My favorite design detail: positioning the microphone gain control so that it can be adjusted without opening the case--it is accessible through the headphone jack. — My favorite design detail: positioning the microphone gain control (the blue square with a white circle, located in the center of the image) so that it can be adjusted without opening the case–it is accessible by inserting a long, insulated, adjustment screwdriver through the headphone jack (the connector to the left of the white cable). Of course, after all this, it didn’t need adjusting.

The finished adapter mounted and ready for service.

Update

This topic has received a lot of traffic, lately, so I thought I’d add some additional links. I’ve not been able to find links to the ARRL references I mention above. When I do, I’ll add them here. Also, I don’t want to give the impression that I invented any of this. The circuit is very common. Mine derives from Aviation Headsets for Ham Radio, which derives from Aviation Headset Connected to FT-897, posted a few years earlier. As I recall, one reference I found for this application was from the 1990’s. I adapted these to my particular application and, if anything, my contribution to the project was in the mechanical design, more than the electrical circuitry. Along those lines, I will say that after the past few years of use, the industrial Velcro attachment method has proven to be quite reliable.

If I had to do it again, I would add an external speaker jack and switch. Plugging in the adapter to the radio’s headset jack disables the radio’s speaker. That’s great when you’re operating by yourself, but when there are people huddled around you who also want to listen (and you don’t want to give up the convenience and clarity of the headset), not being able to also output the audio to a speaker can make things awkward.

For your convenience, and to save you from rummaging through Google, here are some more links on the subject. You’ll notice they have a lot in common, with variations to accommodate their individual applications. Some of the pages were posted since my article, and they are in no particular order. They are here only to help you make the best adapter for your application. Enjoy!

October 19, 2015December 6, 2018

Best practice…for you?

Last week, I saw a post in LinkedIn about a “new” finding (from 2012) that “New research shows correlation between difficult to read fonts and content recall.” First, kudos for not confusing correlation and causation (although, the study was experimental and did prove a causal relationship), but the source article demonstrates an example of inappropriate generalization. To the point of this post, it also underscores the context-sensitive nature of content and how similar advice and best-practices should be tested in each specific context.

Hard to read, easy to recall?

The LinkedIn post refers to an article in the March 2012 issue of the Harvard Business Review. The HBR article starts out overgeneralizing by summarizing the finding of a small experiment as, “People recall what they’ve read better when it’s printed in smaller, less legible type.” This research was also picked up by Malcolm Gladwell’s David and Goliath, which has the effect of making it almost as true as the law of gravity.

Towards the end of the HBR article, the researcher tries to rein in the overgeneralizations by saying (emphasis mine), “Much of our research was done at a high-performing high school…It’s not clear how generalizable our findings are to low-performing schools or unmotivated students.“ …or perhaps people who are not even students? Again, kudos for trying. Further complicating the finding stated by the HBR article is that the study’s findings have not been reliably replicated in subsequent studies, other populations, or larger groups. I’m not discounting the researcher’s efforts, in fact, I agree with his observation that the conclusions don’t seem to be generalizable beyond the experiment’s scope.

Context is a high-order bit

All this reinforces the notion that when studying content and communication, context is a high-order bit¹. As a high-order bit, ignoring it can have profound implications on the results. Any “best practice” or otherwise generalized advice should not be considered without including its contexts: the context in which it was derived and the context into which it will be applied.

This also reinforces the need to design content for testing–and to then test and analyze it.

1. In binary numbers, a high-order bit influences the result more than any and all of the other lower-order bits put together.

October 16, 2015October 16, 2015

Out standing in the field with ham radio

The BigFoot-120 course map — The Bigfoot-120 course map

I had the pleasure of supporting the Bigfoot-120 race, last weekend. For those who, like me, have never heard of such a thing, it’s a 120-mile race that takes place over mountain trails—in this case, the mountain trails between Mt. Adams and Mt. St. Helens in southern Washington state. I was part of the volunteer radio-operator team who set up 10 two-way amateur radio stations around the course. In that part of the state, there is zero cell-phone coverage so, as on my trips to Honduras, the volunteer amateur radio operators provided the only reliable communications to support the race as a public service.

The race

The race started Friday afternoon and the competitors ran on hiking trails through that night, the following day and night, to finish Sunday morning. As if running mountain trails day and night isn’t enough challenge, Mother Nature contributed a series of rain squalls on Saturday. This made it interesting for the runners who had to brave the elements as well as for the radio operators who had to keep their tents, radio equipment, and antennas dry. Fortunately, the weather cleared on Sunday to provide some amazing views of Mt. St. Helens. I admire the competitors for their ability to endure over 36 hours of these conditions…while running up and down a trail through the mountains.

The radio operations

The radio operations were also a challenge. We had to set up our equipment in the rain and dark of Friday night and keep it working throughout the passing rain squalls on Saturday. We used the radios at each of the aid stations to relay information about the participants’ progress to the race coordinator. As runners would pass through each of the stations along the course, their times would be relayed back to the coordinator to make sure every one was safe and accounted for. The radio crews were also used to coordinate the spur-of-the-moment activities that are inevitable when you have almost 100 people running through the woods…at night…in the rain…in October…in the mountains. The radio crews handled their challenges quite professionally.

The radio geekery

The relatively short distance for the radio signals to travel allowed us to use 2-meter (146 MHz) and 6-Meter (52 MHz) VHF/FM frequencies; however, the mountainous terrain required us to relay messages sometimes. Every station could talk to at least one other station, but no station could talk to every other station. The professionalism of the radio team made relaying messages very effective. I sent my wife some email using the WinLink station I took to Honduras; but I didn’t find out until after the race that I could have also used it to send race updates to the outside world. At least we’ll know for the next race.

This adventure was the first in a lot of ways for many people and we all learned from it. The professionalism of the organizers and volunteers made it a success and a great adventure for all.

Official photos from the race

October 4, 2015October 16, 2015

I’m a most-viewed writer

It was fun to see this in my Quora feed, this morning. The stats, however, show my fame might be fleeting with #11 nipping at my heels. But, for the time being, I’ll enjoy my moment in the spotlight. Gaining notoriety wasn’t a particular goal of mine, but I might as well enjoy it and it gives me the opportunity to ponder a few things before I dive into the rest of my weekend chores (ponder spelled: p-r-o-c-r-a-s-t-i-n-a-t-e).

Not many technical writers answer in Quora

This is a shame. To be more precise, the numbers show that not many technical writers answer Quora in the technical writing topics. It does show that almost 8,000 are following it, but I guess I was expecting it to be more popular, given the high quality of discourse between people in such a broad demographic. Even the topics by the most-viewed writer in Quora’s technical writing topics have had only 1,299 views in the past month. I suppose it could be because there are other forums that narrowcast to technical writers–LinkedIn’s professional writer forums are at least 2-3 times more subscribed, for example.

Why Quora?

I like Quora for its variety of topics, variety of contributors, and how they all get along. I like Medium, for many of the same reasons. Even as a pastime, I don’t mind answering the occasional technical writing (a.k.a. work) question, but I just don’t see them that often. A quick review shows that I’ve answered 18 technical-writing posts in the past three years. Statistically, I seem to have more fun (or, perhaps, just more to say) about flying and aviation, in which I’ve written as many answers in the past six months. In fact, my most read post is about an in-flight emergency I had while flying with a friend.

If it takes an in-flight emergency, or something with that level of drama, to make a popular post, it doesn’t seem fair to compare flying to technical writing. Honestly, flying lends itself to those types of stories much more than technical writing does. In all my professional experience, I can’t recall one life-or-death experience as a technical writer, which isn’t a complaint, by the way.

Anyway, check out my posts in Technical Writing—for the content, of course, not just to put some breathing room between #11 and me.

October 1, 2015October 1, 2015

Thinking of Honduras

Photo of Rus Rus Hospital and the Cessna 206 that is used as the Air Ambulance — Rus Rus Hospital and its ambulance

I recently got an email from the International Health Service of Minnesota, (IHS of MN) about their upcoming mission to Honduras. They are recruiting for this year’s mission in the last week of October and next year’s in the last two weeks of February. Unfortunately, I’m not able to go on either, this time, the message did motivate me to publish a short summary of the past trips my wife and I have supported.

I haven’t ventured out on many expeditions like the type IHS of MN runs, but I’ve seen enough large-scale deployments to know a well-run operation when I see one and IHS of MN runs a very tight ship. The dedication of their volunteers and their decades of their experience come together twice a year to provide an effective deployment of medical and dental services to people who would not otherwise receive them. While we aren’t able to go on the upcoming trips, we’re keeping in touch to be ready for the next opportunity.

With any luck, I’ll have edited and published all the photos and videos from the last two trips by then.