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A 1960’s Astatic D-104 Mic in the 21’st century – a real baby boomer

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I made a pass through my basement to see what “valuable radio artifacts” (some call it junk) I could unearth.  I discovered a couple of Astatic D-104 Microphones.  (See more old Mics).  These Mics were made a long time ago and Astatic has a rich history going  back to 1933.

Here is a bit of history from the Wikipedia on Astatic and the D-104

Introduced in 1933, the Astatic model D-104 was popular for its high frequency response which resulted in very intelligible audio.

Its high output voltage was characteristic of crystal elements and its high impedance allowed for direct grid input. The early D-104 mikes used a 1″ thick case and have a large ID tag along with tapped holes for “ring & spring” mounts. The case thickness was reduced in April 1937 and smaller tags were then used and the ring holes eliminated. The “grip” switch stand (“G” Stand) was introduced in January 1938 but didn’t become popular until much later. The early “G” stand bases were gloss black with metal ID tag.

The D-104 continued in production with little change until the 1960s when a solid-state amplifier was added to the “G” stand. In 1976, an eagle and shield was added to the rear cover to commemorate the US Bicentennial. Other variations appeared from time to time until 2001, when production ceased, 68 years after the first D-104 was offered. [4]

The D-104 is often used by CB radio hobbyists and vintage amateur radio enthusiasts as part of their operating activities.

I bought the D-104’s about 5 years ago for use with my collection of vintage Kenwood (see them) and Heathkit (see them) radios.

It Worked the last time I used it !!

Once unearthed I found that one of the D-104’s worked and one did not.  “It worked that last time I used it” is a familiar phrase well known by all  who attend hamfests or flea markets.  At a hamfest or flea market the seller wants to dispose of items in the most expedient way possible.  To say that it worked the last time they used it is a good use of plausibility deniability for the seller (but bad for you the buyer).  If you’re a seller, don’t test the item.  Ignorance is bliss… and this blissful strategy could make a fast sale.  If you are a buyer, don’t forget to ask the seller about the 30/30 guarantee – 30 feet or 30 seconds.  Doubtful you will get any more than this.

But, both D-104’s really did work that last time I used it.  Really, no kidding. So I have plans for both of these D-104 microphones.  Use one.  Gut one and find out why it doesn’t work – (stay tuned for a posting on this)

The D-104 on a modern radio – the Yaesu FT-7800

The Astatic D-104 was designed in the age of tube radios which require a high impedance microphone.  High impedance is usually 5,000 – 10,000 ohms.  Modern solid state radios generally want a microphone of about 600 ohms impedance.

Would the Astatic D-104’s work with my modern Yaesu FT-7800 dual band VHF/UHF radio?   (read my review of this radio)

Nothing like giving it a try.

Spit and Bailing Wire

Since I was not sure if it would work I jury rigged a setup using a terminal strip, alligator clips, a telephone extension cable, and some paper clips.  It took about 10 minutes to set this up.

Read the rest of this entry »

Written by frrl

January 28, 2012 at 8:24 am

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