Cable TV Question - STD/HRC/IRC

[slu]

I don’t know the difference between HRC/IRC/STD Cable settings on my TV.

It is very difficult to discern the difference between these settings when I change them on my TV.

I have Comcast Digital Cable and I live in Philadelphia. Can anyone explain the difference and what my optimal setting would be?

I tried to search, but you can’t search on HRC and IRC and other searches returned far too many results to browse through.

[gotpasswords]

Swiped from a site that also did a little swiping:

“HRC” is harmonically related carriers. “IRC” is incrementally related carriers. These are schemes that some cable systems use to reduce the visibility of beat products.
"By harmonically relating the carrier frequencies themselves it is … possible to improve system performance. This does not reduce the beats produced, but positions them within the system transmission spectrum such that they are more tolerable. In effect, all signal carriers are spaced precisely 6 MHz apart, thus all beats generated are at 6 MHz increments.

“Since the television signals are vestigial sideband modulated, if the beat products can be manipulated to fall on or near the RF carriers themselves, they are much less offensive…”

–from William Grant, Cable Television, 2nd edition, GWG Associates, Schoharie, NY, 1988, page 82

Getting this setting right used to be a big deal, but now, almost all tuners are “frequency agile” which means they can self-adjust and adapt to whatever’s being fed to them.