Building your own headset microphone means solving some
electrical and some mechanical issues. Electrical, in
the sense of connecting the microphone element to the
microphone jack of the airplane, and mechanical, which
addresses the issues of how to support the microphone on your
It's pretty straight-forward, really: There are two contacts on the microphone element, and they have to be wired to the ring and sleeve terminals on the microphone plug.
That is literally all there is to it. The schematic on
the right shows the connectivity. The mike plug end has
three electrically-separated sections, and the microphone
element is connected to the sleeve portion (the longest
section closest to the middle) and the ring connection (midway
between the tip and the sleeve.
Pretty darn simple...and it's too darn easy to wire to the
TIP, instead of the ring. Watch that.
Why is the Tip left blank? Because it's used for the
push-to-talk switch. Connect the tip to the sleeve, and
the radio PTT is activated. That's usually on the
aircraft side of the interface, and you shouldn't have to
worry about it for your homebuilt headset. The existing
PTT switch will work fine.
I like to use shielded cables to connect the microphone, as
stray signals can feed back. I use ordinary audio cable,
the kind of stuff you use to connect speakers to
stereos. Connect the shield part of the cable to the
sleeve on the plug.
The microphone element has two sockets with set screws for
accepting wires from the plug. As I mention in the main
article, 12-gauge Romex wire is perfectly sized. But
it's really a lot easier to use a U-173/U microphone
attachment plug. This is a little assembly that costs
just $2 and includes everything needed. Buy several.
It's good we know how to wire up the
microphone element, but it doesn't do too much good if the
microphone element isn't supported by your lips. We
need some sort of structure to hold the mike. On a
standard headset, the microphone boom just connects to the
ear cups. But we're using ear buds for our homebuilt
headset, so that's not an option.
Compared to the microphone, there's little work
required for the headphones.
Just about any commercial ear plug/ear bud will
work. I have a set of ear buds that actually an
automatic noise limiter (ANL), like the
top-of-the-line aircraft headsets. These were
expensive for ear buds ($100) but it's still hundreds
less than a standard ANL headset.
I found a better options: Plugfones.
These are foam ear plugs with speakers built into
them. They have passive noise attenuation equal
to those of a standard headset, and provide very good
volume to the ear. What's more, they're cheap
(about $25) and you can buy spare ear tips cheaply as
I *really* like
these. I hate standard ear buds because they're
hard; these are soft and very comfortable.
They actually have two types of ear tips. One
is the standard, foam like the typical ear
plugs. The others are flanged silicone rubber,
similar to ear plugs used for percussive sports like
One huge advantage of these is their low cost:
You can put a spare set or two in the airplane, and
have some backup headsets.
The big DISadvantage of these is that they have an
8-ohm impedance. Standard aircraft radios expect
speakers with 300-ohm impedance, and these won't work
without a matching transformer.
But if you're connecting your homebuilt headset to a
handheld radio, you don't NEED a matching
transformer. The handhelds want an 8-ohm
speaker, and that's what ear buds supply.
So all you need is a way to plug the 1/8" plug for
the ear buds into the 1/4" jack on your radio's
headset adaptor. That's real easy, nominally...
they sell simple adaptors that allow plugging-in a
1/8" plug into a 1/4" jack. Often, these
adaptors even come with your ear buds.
However, there's a problem: The ear buds (and
adaptors) are set up for stereo (two audio channels),
but the radio only outputs one. That means only
one of your ear buds will work.
You can get around this by modifying an adaptor as
shown below. Cut a slit between the tip and ring
of the adaptor, then fill the slit with solder to
connect the tip and ring. I used a Dremel tool
with a cutting wheel to cut the slit, but you can
probably do the same thing with a triangular
file. Just smooth the solder down afterwards so
it goes into the jack without effort.