STB Signal Strength

[hartmang]

Have A Scientific Atalanta STB 8300 HD/DVR connect with HDMI cables to a Phillips 37 inch LCD. Everything looks pretty good HD and non HD channels. Out of curiousity I checked the signal strength to see what it was, possibly to see if my HD picture could be improved. Here is what is gave me:

HD Channel: +8

Digiatal Channel (non HD): -4

S/N Ratio: 35

Does this make since to be that far apart?

I noticed from this forum, that the range is -10 ....+10

I was wondering if my HD signal is good or not?

Thanks for any recommendations.

[mjones73]

Are you having any issues with your HD PQ?

[hartmang]

No, not really. Just wanting to have best PQ that I can possibly have. I live in a older house, and about three months ago prior to getting the HDTV, Comcast came out and added a booster i believe to increase signal. Just wondering if I should call them up and check into the numbers i got.

[kevinw]

Have you used any type of home theater tune up disks like Avia, Sound and Vision or Digital video esentials? Or at least use a DVD with THX? Usually a better picture comes from having a properly adjusted TV.

[mjones73]

With digital, either you have a picture or you don't, if you aren't experiencing any break ups or other issues, bumping the signal strength more isn't going to change the PQ.

[hartmang]

SO the + 8 reading on the HD channels is good?? Really that is all I am concerned about, as far as signal strength...

[Ratman]

Even if you had -8, as stated earlier, if you don't have any "breakups" or other issues... there's not a problem to fix.

[57U]

That sort of difference in signal strength is a bit unusual, but not unheard of. I'd think it MAY be due to a poor splitter upstream (not rated for 5-1000 MHz for example) or the use of RG59 instead of RG6 RF-coax upstream, or simply something in the service provider's distribution. I'd check for the former two inside your home and not worry about it if those are OK.

[Ratman]

I'd lean on the side that it's not a cable type or splitter problem, but perhaps the way the STB interprets the signal(s).

HD and non-HD is both digital (excluding analog channels >99). The difference may be that QAM64(non-HD) signal levels are calculated differently than QAM256(HD) with that STB (just my SWAG).

As for the cable type... signal loss over distance could be a factor when comparing RG59 to RG6 at certain frequencies, but this should not matter with the "acceptable" levels that are being observed.

If it were due to an underrated splitter, then some channels would simply not work at all.

[57U]

Ratman, I'm not sure, but in the following table it shows higher dB losses at higher frequencies, so the channels at those higher frequencies would be affected more, if there were a significant cable length or a poor splitter. You are correct that at some point the chnanel would no longer come in at all, but if the signal is adequate, then only the signal strength would be affected.

http://www.radio-ware.com/products/techinfo/coaxloss.htm

http://www.dslreports.com/faq/cabletech?text=1

For example, at 100', the RG59 (labelled 58 in the first chart) has almost 10dB more loss than RG6 at 700 MHz than at say a lower frequency .

[Ratman]

RG58 is 50 Ohm that (AFAIK) would never be used for CableTV.

http://home.datacomm.ch/hb9abx/coaxdat.htm
http://www.pfm.howard.edu/infosys/typicalcoaxfeatures.pdf
http://www.pfm.howard.edu/infosys/choosing_correct_cable.pdf

[57U]

RG58 is not the comparison I was trying to make. I was assuming that was a typo in the chart since the second chart looked simlar and was labelled RG59.

The point that I WAS trying to make was that cables/splitters can affect different frequencies to a different extent and therefore MAY contribute to different readings on different channels (frequencies).

[Ratman]

I agree... but the attenuation chart you provided and I provided are quite different (between RG59 and RG6). ;) Which one is correct?

But, I still contend that with the ratings the OP registers on his STB are in acceptible ranges and should not probably be of major concern, unless there is a problem with dropouts. One could get into the nitty-gritty if necessary to determine what channels and the frequency used are problematic. Since HD channels are "high" and digital non-HD are "low", I'd suspect the measuring algorithm in the STB (I could be wrong).

As for the spiltter (if used), I wouldn't highly suspect that as an issue since a splitter generally does nothing more than halve the power (with a two-way).

[Splicer]

It all depends also what channels are being checked for levels as to if it is high or low...As the others have stated...if you are not experiencing any problems, then there is nothing to fix...