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The RCA Type 74-B Junior Velocity
is a bi-directional ribbon microphone.

RCA Type 74-B

The RCA Type 74-B “Junior Velocity”

RCA 74-B Junior Velocity

Copyright © 2005 by Sean Brady.
Used here with permission.
Not for other publication, distribution, nor resale.

RCA 74-B Junior Velocity

Copyright © 2005 by Sean Brady.
Used here with permission.
Not for other publication, distribution, nor resale.


This is an MI-4010-A, predecessor of the Type 74-B.
Notice the two grille screws at the top rather than at the sides, the
separate side grilles, and a stand mount that does not include a swivel.

RCA 74-B

This 74-B was auctioned for $600 on eBay in June, 2002. View a 74-B with its grilles off.


  • Free from objectional peaks or dips from 70 to 8,000 cycles.

  • Bi-directional “figure eight” type pattern which allows placing of artists on both sides of the microphone and greatly reduces reflection pickup from side walls.

  • Light weight, small size.

  • Attractive appearance.

The 74-B has been widely used by broadcasters for years. It offers the smooth bi-directional response of the 44-BX in an inexpensive, small and light-weight model. The 74-B is par­ticularly recommended for applications where the extended frequency response and more elab­orate shielding and shock mounting of the 44-BX are unnecessary. It is, therefore, a useful microphone for audition studios, announce po­tions, talk back and for small and occasionally used studios. It may also be used for remote pickups where the frequency response is limited by lines and other factors. While the 74-B is particularly useful for pickups from inside remote points, the Type 88-A Microphone is especially suited for general remote use. It is designed to give the greatest freedom from effects of wind, shock and moisture.

RCA Type 74-B

In design the Type 74-B is similar to the larger 44-BX, but lacks the latter’s shock mount and transformer shield­ing. Transformer output impedance taps are for 50, 250, and 15,000 ohms. The windscreen is finished in satin chro­mium and the base is umber gray. Attached to the base is a ball and socket joint that permits rotation or tilting at any angle.

New ribbon

A new ribbon

Ribbon and magnet assembly

The magnet and ribbon assembly


An educational note on the “silks”
The fabric that lines the grilles is called “silk,” but originally it was 100 per cent cotton cambric, also used across the bottoms of sofas and chairs by furniture manufacturers of that era to keep bugs and dust out. The cambric was cut to size and applied to the microphone grilles with shellac, then smoothed and worked by hand with alcohol, which kept the shellac from clogging the weave of the cambric, but allowed the cambric to stick to the metal grille. Other techniques are used today, such as spray adhesive.

—Thanks to Gary Sanders and Jon Sank for this information.

Advertisement 74-B polar response

Polar Response

74-B Frequency response

Frequency Response


Download this Circuit Diagram as a PDF.


Source unknown

Bill Shadel covered D-Day for CBS Radio, became an ABC television anchor, and moderated the third presi­dential debate between John Kennedy and Richard Nixon in 1960. Mr. Shadel, who worked with Edward R. Murrow, Walter Cronkite, Eric Sevareid and Howard K. Smith at CBS, later became a com­muni­ca­tions professor at the University of Washington.
As did many American broadcast personalities of the day, Walter Cronkite lent his support to the work of the Radios. Cronkite narrated Towers of Truth, a film about Radio Free Europe’s work commissioned by the National Committee for a Free Europe in conjunction with the Crusade for Freedom fund-raising efforts.

Steve Mendelsohn, W2ML, was Cronkite’s radio engi­neer at CBS for many years. “I had many chances to discuss my favorite hobby, ham radio, with ‘the world’s most trusted anchor man,’ ” he told the American Radio Relay League (ARRL). “Gradually, his interest increased, but on finding that he had to pass a Morse Code test, he balked, saying it was too hard for him; however, he told me he had purchased a receiver and listened to the Novice bands every night for a few minutes. At the CBS Radio Network, Walter would arrive ten minutes before we went on the air to read his script aloud, make corrections for his style of grammar and just get in the mood to do the show. In those days Rich Moseson, W2VU, was the producer of a show called In the News, a three-minute television show for children voiced by CBS Correspondent Christopher Glenn. On this day, Rich was at the Broadcast Center to record Chris’ voice for his show and had dropped by my control room to discuss some upcoming ARRL issues.” At the time, Mendelsohn was the ARRL Hudson Division Director.

“When Walter walked into the studio, I started to set up the show at the behest of our director, Dick Muller, WA2DOS,” Mendelsohn recalled. “In setting up the tape recorders, I had to send tone to them and make sure they were all at proper level. Having some time, I grabbed The New York Times and started sending code with the tone key on the audio console. For ten minutes I sent code and noticed Walter had turned his script over and was copying it. We went to air, as we did every day, at 4:50 p.m. and after we were off, Walter brought his script into the control room. Neatly printed on the back was the text I had sent with the tone key. Rich and I looked at the copy, he nod­ded, and I told Walter that he had just passed the code test. He laughed and asked when the formal test was, but I reminded him that it took two general class licensees to validate the test and he had just passed the code. Several weeks later he passed the written test and the FCC issued him the call KB2GSD.”

Mendelsohn helped Cronkite make his first Amateur Radio contact: “Having passed the licensing test, Walter was now ready to get on the air. His first contact was on 10 meters at about 28.390 MHz. He was nervous and I called him on the phone to talk him through his first experience. As we talked on the air, a ham from the Midwest came on and called me. Acknowledging him, I asked the usual questions about where he was, wanting to give Walter a bit of flavor of what the hobby was about. I turned it over to Walter, and following his introduction, the gentleman in the Midwest said, ‘That’s the worst Walter Cronkite imitation I’ve ever heard.’ I suggested that maybe it was Walter and the man replied, ‘Walter Cronkite is not even a ham, and if he was, he certainly wouldn’t be here on 10 meters.’ Walter and I laughed for weeks at that one.”

Brandon Chase
Brandon Chase, a disc jockey at WNLC in the fifties, also conducted inter­views and did a bit of field reporting as well. He tells an interesting tale of jumping onto the caboose of a train to try and get a better recording (on a wire recorder) of Harry Truman, and being batted off by the secret service.
Franklin Delano Roosevelt
                             President Franklin Delano Roosevelt.
4010 cover

Download the MI-4010-A data sheet (1935).

74-A cover

Download the Type 74-A data sheet (1936).

74-B cover

Download the Type 74-B data sheet (1940).

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