Doh! Adding power for uncorrelated sidebands should be a factor of 3dB, not 6. So much for that theory... Perhaps the specification has been somewhat revised relative to the document I Googled.
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--- In ultralightdx@..., "sdwillingham" <sdwillingham@...> wrote:
I got the -25dB number from an iBiquity document (the inventors and promotors of IBOC). Since the two sidebands are uncorrelated, the total power in both sidebands would add up to -19dB (-25 + 6) relative to the main signal. But as far as obliterating a station on one side of the carrier, it's probably the -25 dB number that applies. Then again, I'm no expert on IBOC.
Regardless of the actual number, we agree that the principle of IBOC sacrifices adjacent-station DX reception for providing "improved quality" of local stations.
--- In ultralightdx@..., "ferrite61" <dxrx@> wrote:
From what I have read on the internet, iBOC is usually transmitted at -19db relative. Thus a 50kW atation broadcast iBOC at about 630 Watts. Due to the nature of the signal, it interferes directly on adjacent channels with nearly full effect. In CT 1080 WTIC at 35km obliterates 1070 and 1090 at nite. Only a high-power signal at distance can cut through.