[XCSSA] OT: Built my own DTV antenna

[X-otic Computer Systems of San Antonio]

>
> Can somebody explain in laymans terms "extraneous harmonics"? I'm just
> curious because I'm NOT using an amplified antenna so I shouldn't be
> affected by this problem.

Probably what they're talking about is harmonics at the DTV  
transmitter.  Such things were quite common in the early days of FM  
radio when some broadcasters frequently overmodulated, through  
carelessness and/or design.  Now everything is computerized, so one  
wouldn't expect that to happen so much, though possibly some stations  
push their output levels as high as they can while staying within the  
measurable limit for harmonics.

Wouldn't think that would happen with modern DTV transmitter, though  
once again small amounts of harmonics might be inevitable and legally  
permitted.

Also, receivers can also function as low level transmitters to some  
extent.  Some FM tuners are notorious for this.  Turn on tuner A and  
then tuner B, right next to it, no longer works because A is putting  
out so much RF garbage.  I have a Kenwood 600T from 1977 which is  
like that partly because it uses a second mixer as part of its "pulse  
count detector".  Kenwood later switched to an even better detector  
technology that didn't produce this problem.

Likewise with broadband antenna amplifiers, if you had one.

I wouldn't think that would be a problem with recently designed DTV  
tuners, but who knows.

Your problem may stem from some sort of wideband RF noise that is  
affecting both bands.  Impulse noise (such as from automobiles,  
motorcycles, etc., especially with old fashioned ignition systems, or  
heavy motorized machinery...maybe even an A/C system) can be like that.

Great observation, noting this correlation!

Charles Peterson

>
> -- 
> Jeremy Mann
> jeremy at biochem.uthscsa.edu
>
> University of Texas Health Science Center
> Bioinformatics Core Facility
> http://www.bioinformatics.uthscsa.edu
> Phone: (210) 567-2672
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