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Wednesday, January 18, 2006

 

HD digital radio-FAILS AGAIN!-(for broadcast engineers)

A large bird squatting on the tower can change everything, and IMHO "annual" mask measurements have become a joke with the advent of NRSC-5.
On 26 Nov 2005 at 3:00, Alan Alsobrook wrote:> In actual practice it does seem to be hitting up to the 3rd on a few > I've listened to. I must admit that this was simply consumer receiver
> listening. So I can't say much as to the reason, be it receiver induced > or excessive bandwidth from the source.All I can say is I've seen Richard Hinkle's demo of adaptive predistortionwhere there was plenty of garbage at +/- 20 kHz around -70 with some showing up at +/- 30 kHz; then about 30-45 seconds after doing the Capt.Picard "Engage" number, all is clear above -90 at both second and third.Truly amazing.Considering the variations typical in DA operation, and for that matter,in a simple ATU/tower combination with temperature and moisture variation,I don't see how it will be possible to operate MW-IBOC/HD without a predistorter and continuous monitoring such as Belar is bringing to marketsoon.Maybe it's just me, but I don't see how you can KNOW what your emissions are unless you watch them. A large bird squatting on the tower can change everything, and IMHO "annual" mask measurements have become a joke withthe advent of NRSC-5.
Phil Alexander, CSRE, AMDBroadcast Engineering Services and Technology (a Div. of Advanced Parts Corporation) Ph. (317) 335-2065 FAX (317) 335-9037

Source:
http://lists.radiolists.net/pipermail/tech-zone/2005-November/000147.html

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