Re: [IRCA] [NRC-AM] More IBOC In Philly

IBOC is accomplished by a separate audio chain and RF generation set.

See http://www.nautel.com/products/index.php?group=23 for a description of one manufacturer’s gear. A lay explanation is at http://www.ibiquity.com/technology/hdradio_how.htm and the iBiquity site has a number of white papers, which, despite the obvious bias towards the system, do describe the technical aspects well and correctly.

AM stations combine the two signals, analog and digital, and they are, in a manner of speaking, diplexed on or into the same antenna system.

The digital signal is about 10% of the analog signal in power output to the transmitter. However, as several posters on the NRC reflector have posted, the way the digital signal is constructed makes it “appear” to have more power, and, because it is digital, it will cover in usable fashion as much and sometimes more usable geography than AM. At KTNQ we have found that the IBOC signal is usable in a number of areas where the analog signal is overcome by objectionable noise or interference.

From: irca-bounces@xxxxxxxxxxxxxxxx [mailto:irca-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Milspec390@xxxxxxx
Sent: Friday, September 23, 2005 8:47 AM
To: irca@xxxxxxxxxxxxxxxx
Subject: Re: [IRCA] [NRC-AM] More IBOC In Philly

Hi Patrick -

Uninformed questions re IBOC power. Are IBOC mitters separate from analog? Either way, are HD signals pulse-like? If so, would peak power be much higher than average? No doubt many explanations for listener reports indicating high power despite claims to the contrary.

Mixing apples with kumquats by comparing w/radars such as FPS-35, in which pulsed 50 Kw amplitrons produce 5 Mw out. Canaveral lift-offs were detected from Thomaston, AL and Manassas, VA despite low-average transmitter power. Peak power carried the day.

If IBOC sigs pulse-like, would this explain much higher level of received noise despite claimed low average power? If interference nil and HD power trifling - as some claim - why would anyone bother?

=Z.=

Paul Vincent Zecchino
ManaAmplitron Key, FL
BT