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Letters: General Phones, AM Radio and Musing about 600 Ohms

Readers comment on recent Radio World articles

Here are more letters to the editor from Radio World readers. You can submit your own to [email protected]


A General, Not a First

Re: the recent letters about FCC licenses:

Following the demise of the First Class Radiotelephone License, there was a brief period of time when the holder of a First Phone License could have it replaced with a General Radiotelephone Operators License, as contrasted with later issuances of General Radiotelephone Certificates.

See the accompanying image of my General Radiotelephone Operators License, which replaced my First Phone.

– Xen Scott

 

OK, Now What?

Re: “Auto Industry Non-Committal to Keeping AM in New Cars,”:

Man, the work I did with General Motors years ago, to show them that AM was worth keeping … So what will the commission do about the translators tied to AM stations that will no longer be received in cars? Will they allow licensees to turn off the AM and keep the translator going? Widespread HD adoption isn’t enough to keep this from happening?

– Jonathon R. Yinger

President/CEO, The Christian Broadcasting System & Broadcast Properties LLC

 

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.

[Read more reader letters.]

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