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Audio Basics, Part 1:

by Mark Persons
Radio World
February 1,

Mark Persons, WØMH is an SBE Certified Professional Broadcast Engineer and is now retired after more than 60 years in radio broadcast engineering, including 44 years in business. He started by turning the dials of broadcast transmitters at age 11 and stays active by mentoring four radio broadcast engineers.  Mark is also a member of the National Radio Systems Committee. His website is

Email comments from readers:

02-14-2023: Mark, As always, I enjoy your articles in Radio World and I am glad to see you continuing to educate younger generations!  John King, Jacksonville, Florida.



02-14-2023:  Great Aricle Mark, Loved the latest article!   It's funny because video is so easy compared to audio!  Though your article is more about the technical side, one of my "basics for audio for radio" is that WAY too many broadcasters don't know, understand, , or maybe "care about."  And, too many people don't understand levels as they relate to digital and analog.  I've always said, digital has ZERO headroom.  NEVER approach "100%" with digital  because anything above 101% is "gone forever" (clipped, distorted, flat-lined).   At least analog always had a little headroom (depending on the quality of the gear.. some had more than others).  Anyhow... thanks for a great article!!  Dan Slentz, Cleveland, Ohio.


04-19-2023:  Radio World, 600-Ohm Musing

Regarding Mark Persons’ article “Let’s Talk About Some Basics of Audio for Radio” in the Feb. 1 issue:

Mark, some questions regarding 600-ohm termination:

  1. Do I understand you to say that with modern transformerless equipment, it is not necessary to have 600-ohm terminations? Does it make a difference if there is a long run of wire to the destination?
  2. With legacy equipment that has an actual 600-ohm output, will a 600-ohm termination reduce the voltage by half? Is the VU meter calibrated assuming a 600-ohm load?
  3. When setting levels, is it less critical if there is compression between the studio and the transmitter?

– Kenneth Lundgren

Author Mark Persons replies:

Kenneth, transformerless equipment does not require a termination to keep audio frequency response flat. A long run of cable is more difficult if it is more than several hundred feet. In that case, likely a termination should be used.

VU meters on transformer output equipment are calibrated based on a proper termination. Yes, the audio is higher without a termination. Best to set all levels within a few dB so the audio processing does not need to work as hard to maintain the correct level. If the audio processor sees a much higher level when a new source is connected, audio distortion might result during the first second it is on.

Conversely, a lower audio source will sound low until the processing catches up. Listeners hear those less than great transitions between program material sources.

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