I notice that numerous Audacy AM stations have been filing “Modulation Dependent Carrier Level” (MDCL) notifications today. I understand what MDCL is, but am curious about why these filings are now being submitted?
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Audacy MDCL filings
- Thread starter Mediafrog+
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Maybe they want to save money on the power bill, if they’re for high powered stations.
The technology has been around for several decades; many high powered shortwave transmitters have used it since the 1980s. Most of the filings are for Audacy’s 50kw stations. Just curious why “all at once”.
As I understand it, in the US MDCL reduces carrier level in the silence between words and is effective on talk stations. In Europe MDCL increases carrier during the silent period to reduce noise. With all of the RF noise around, the European method actually seems more beneficial and would have similar power savings. Any thoughts from the wizards out there?
Like Europe, in the U.S. Canada Mexico, MDCL decreases the carrier during audio. Full power with no audio.
(I'd upload a SMALL video but it seems everything is too large for this site.)
Here’s a slideshow on MDCL prepared by GatesAir’s Tim Anderson. There’s more than one way to do MDCL, although Audacy is proposing using the so-called AMC method on all of the applications that I saw. That method reduces the carrier level when modulation levels are high.
MDCL Technologies
MDCL Technologies
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MDCL is real easy to get working on the Nautel NX series of Transmitter, you just program it into the preset. If Audacy has NX-50 transmitters at these station and they were not using MDCL it's a great way to save money. More savings can be realized if the transmitter has a closed air system and an air conditioner is used.
Another power saving technique that has been tried on shortwave is AM Compatible Single Sideband, or AM-CSSB. The carrier is somewhat suppressed, but still sufficient to be listenable on a standard receiver. In addition, only one audio sideband is transmitted.
I recall that Radio Netherlands used AM-CSSB on one of its North American beams from Bonaire in the 1990s. The spoken word audio was quite clear with a good amount of punch, although music could sound a little rough at times. When you "tuned through" the signal it was asymmetrical due to the missing sideband.
Canadian time signal station CHU uses AM-CSSB, with only the upper sideband.
I recall that Radio Netherlands used AM-CSSB on one of its North American beams from Bonaire in the 1990s. The spoken word audio was quite clear with a good amount of punch, although music could sound a little rough at times. When you "tuned through" the signal it was asymmetrical due to the missing sideband.
Canadian time signal station CHU uses AM-CSSB, with only the upper sideband.
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