CBC AM 690 signal

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CBC AM 690 signal

Postby kal » Sun Nov 22, 2015 8:35 am

For the past few Sundays I've noticed that in the early morning the AM 690 signal is much weaker than it usually is. In fact before 7 am it appears to be weaker than that of KFBK or KGO. My observations are strictly anecdotal. All I know is that I have to turn up the volume on my trusty Grundig compared to the level I have for the rest of the week.

What's going on?
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Re: CBC AM 690 signal

Postby jon » Sun Nov 22, 2015 9:19 am

Historically, CBU and the former KING-1090 in Seattle played classical music during all or part of their broadcast schedule. Purists among the CBC/KING staff or listeners insisted on hearing the full dynamic range (AKA loud versus quiet passages) of that music as originally recorded. To do that meant what I would call "one-sided audio compression": installing a Peak Limiter to prevent Overmodulation, but not boosting periods of lower volume (low percentage of Modulation).

Decent DX radios do a great job of boosting weaker signals, by monitoring the signal strength and adjusting the amplification so that "all" signals are at the same audio level to avoid you having to adjust the volume control all the time. They get fooled by radio stations that "Undermodulate" as it sounds like CBU was doing during the time periods you mentioned.

As to why that happened in this day and age is likely a CBC Vancouver operator not setting the volume correctly on his console.
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Re: CBC AM 690 signal

Postby radiofan » Sun Nov 22, 2015 10:13 am

The 690 signal has been weaker than it was for the past few months, and there are frequent drop outs resulting in dead air for a few seconds.

There was a scheduled shut down of 690 last weekend for maintenance, but I don't know if that actually happened (they weren't off the air for the 3 or 4 hours that was mentioned the previous week on North By Northwest and listeners were told they'd still get the show on 88.1).

Even with the weaker signal these days, it's still much better than it was years ago when XETRA caused nightly interference.
Those who danced were thought to be quite insane by those who couldn't hear the music.
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