3 HDTVs yet two different channel maps with cable

[Anonymously Submitted]

I hate to admit that I am an experienced IC design engineer that worked in the group that put the first ICs into RCA receivers as well as t he early development of HDTV. But, I just do not understand what is going on in these early days of HDTV implementation!

Does anyone have any knowledge of what the cable companies and set manufacturers are doing today? I have three HDTV sets. Two are Samsung and one is a Mitsubishi. When connected to the same antenna connector individually they all receive different stations. One will tune channels 2-1 and 7-1, another will tune 4-1 and 9-1, etc. One common denominator is that the sets must all "scan" the channels before any HD stations can be tuned. If they are not captured during the scan, there is no way you can tune them individually later. The digital tuning strength meter included in the receivers all indicate the received HD stations are quite strong.

So in summary, is the type of problem I have described a problem with the way the cable companies are now inserting "clear QAM stations" or is it a a problem with the tuning algorithms or sensistivity of the TV tuners themselves?


This has been causing me an enormous amount of frustration and I am sure others are similarly inflicted but may not be able to explain in succincttly.

Thanks,
Steve

[Richard]

Don't have an answer - first time it has come up. This may help...

ATSC Cable QAM Tuners - CableCARD or ATSC Ready
http://www.hdtvmagazine.com/articles/20 ... _ready.php

CableCARD Basics
http://www.hdtvmagazine.com/articles/20 ... basics.php

[akirby]

I suspect the difference is how each set interprets and displays the channel number. Each digital channel has a physical channel number and a virtual channel number, just like ATSC. E.g. in ATSC our local analog channel 2 broadcasts in ATSC on physical channel 39. But the virtual channel number is 2-1. The TV/receiver could display this as 39-1 or 2-1 depending on whether it was using the physical or virtual channel number. The virtual channel number is sent in the digital data stream.

Just a guess. If they're using the same cable signal then all tvs would be getting the same input - only explanation is they're using different sources for the channel number.

[Richard]

If the above is the case then that would infer the firmware in one of the displays is not setup correctly for the PSIP - that is where the virtual channel info comes from as I recall.

[dabhome]

Are they actually different channels or just labeled differently?