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
omments from readers:
02-14-2023: Mark, As always,
I enjoy your articles in Radio
I am glad to see you continuing to
educate younger generations!
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,
Regarding Mark Persons’ article “Let’s
Talk About Some Basics of Audio for Radio” in the Feb. 1
Mark, some questions regarding 600-ohm termination:
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
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?
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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