AL7X Station - Part F:

The Microphone and Key

Updated 11/9/2013

The Microphone here at AL7X is the Astatic D104

In 1930, a couple of ham radio operators, Creed Chorpening, W8WR (later W8MJM), and F.H. Woodworth, W8AHW, were trying to come up with microphones that had the quality necessary for their ham sets. Charles Semple, a friend, had been experimenting with Rochelle salt crystals. Semple demonstrated some crystal pick-ups.

Chorpening and Woodworth both recognized that the crystal microphones provided excellent quality audio and would be perfect for use on their ham radios. As a result, Chorpening and Woodworth started "The Astatic Microphone Laboratory, Inc." in Youngstown, Ohio in 1933. Semple was hired as General Manager to manufacture and market the first line of D-104 Crystal Microphones.

Astatic soon became a leader in Microphone and Record Player Turntable pickps. In World War II they produced various products under war time contracts. They designed and built the Sonar undersea microphone for submarines.

As with all name brands, some conglomerate picked up the Astatic name in 2001, and production of the D-104 ceased.

The above historical excerpt based on work of K3DAV.

The manufacture of D-104 microphones did not change for the 68 years it was in production. The microphone cartriges are still available; the entire housing, stand, etc. was produced until the very end. The stands, while looking identical, had some later models with Transistorized amplifiers introduced in 1962. My own D-104 has such a stand; I assume the microphone head is from the same date as the stand. Look in eBay for a selection ...

I wired it to my Icom 7410. I connected the microphone internals so that there is continuous audio from the Mic to the radio, allowing me to use Push-to-Talk (PTT) or Voice-Operated-Xmit (VOX) as selected by the ICOM.

Then I called Dennis Weidler, KL1OE, manager of KICY and a connoseur of quality audio. I set up a simple test on ten meters, with Microphone A being the D-104, and Microphone B being the stock Icom hand microphone for the IC-7410 radio. I did not tell him which mic was which.

He said that microphone A was head and shoulders better, with better fidelity, punch, presence, clarity and ease of listening to compared to Microphone B. Of course, Mic A was the D-104.

Not bad for a Microphone now 80 years old!

The Telegraph Key

No apologies or excuses, I am a CW man by choice. I love morse code, it sings to me, and I can do decent speed on it. It is my mode of choice.

To produce this music, I use a Vibroplex Vibrokeyer. It is fashioned from the early bug key designs of Vibroplex.

In 1903, the Vibroplex corporation produced a semiautomatic telegraph key. The motion was side to side, rather than up and down. Pushing the paddle to the right produced a dash as long as the paddle was held to the right. Going to the left, a spring would oscillate and send a series of dots.

This design allowed the telegraph operator to send code for hours without fatigue or "glass arm" which is what they called Carpal Tunnel Syndrome in those days. The medium in 1903 was usually land line telegraphs, notably the railroads.

As wireless radio gained popularity, many bug keys were sold to wireless hams and commercial stations. These keys are still produced and sold Today, 110 years after they first rolled out of the assembly line.

As technology progressed, electronic keyers -first with vaccum tubes, and later with transistors - appeared. The electronic keyer is somewhat easier to adjust and produces not only the automatic dots, but also the dashes can be automated.

Two such camps exist. The model I have has a single paddle, and produces dots to the left and dashes to the right.

The other mode uses a dual paddle, one for dots and one for dashes. This mode uses Iambic which allows for some letters to autocomplete by holding both paddles together. The paddles are squeezed with the dot or the dash leading, and thus a dot and a dash are sent with just one motion of the hand.

This can be kinda nice, but I am old dog and my wrist was trained on a straight key and a regular bug in 1959. Thus the Iambic keyer does not suit me.

The Icom 7410 has a built in electronic keyer, it can be set for straight key, bug key (dash as long as lever is held), automatic dashes, or Iambic. I have mine set for automatic dashes using the Vibrasender single paddle key.

Vibroplex, of course, will sell you a straight key, a mechanical bug, a single paddle or dual paddle key. They come in a variety of styles and finishes, from painted steel to gold plated. Your wallet, pride and preference will dictate the choice!

Part A: The Tower
Part B: Temporary 20m Dipole
Part C: The Hex Beam
Part D: Aiming the HF Antenna
Part E: Icom IC-7410 Radio
Part F: AL7X goes Digital!
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Copyright 2013, Ramon Gandia