Archived from groups: alt.tv.tech.hdtv (
More info?)
Dennis Mayer wrote:
>
> Ben wrote:
>
>>TW reviewed my cable signal levels and suggested since I was on the border
>>of not enough signal (-7DB to -9db after a 2 way splitter for vcr/tv) to
>>install an amp. They installed the amp with one output to a six way
>>splitter. This brought the worse case signal to +6db. They then put a 6db
>>reducer to the input of the amp, which gave me 0db at the tv. Should this
>>reducer be at the input of the amp or at the output? It seems like you would
>>not want to reduce the signal to be amplified?
>>
>>Thanks for your time,
>>
>>Ben
>
>
>
> Ben:
>
> I have TWC in NE Wisconsin.....
>
> I have a SA3250HD box & Sony 34" 34HS510 TV..... for 1 year now...
>
> I had an intermittent HD cable signal problem
>
> during my 1st 2 months and then bad after INHD & INHD2 were added.
>
> Initially problem was frequent, 1/2 hour pixelation on many HD
>
> channels... Then it was a HD white screen on INHD & INHD2 only
>
> & just after these 2 HD channels were added...
>
> I talked to the local TWC Engineer and asked for there best
>
> GBay, WI Cable tech.... He arrived in 40 minutes (6 PM) and
>
> recorded HD Cable signal strength... It was -37 db at the
>
> Sony HD input port... -37db is Terrible, terrible bad...
>
This is impossible for an Scientific atlanta receiver, at -37dbmV you
should get a black screen and if sometime you get a picture that means
that you have a bad connection somewere...
> A good & proper Signal is +1db to +10 db before the SA3250 HD box
>
> and 7 db less/ off the +1 & +10 value after the 3250HD box...
>
> Readings were made at the house wall outside, in the basement,
>
> and before & after the set top box (SA3250HD). All readings were
>
> with the portable TW Cable instrument readout except for the
>
> after SA3250HD reading... Last was done with the 3250HD
>
> Set Top Box maintenance menu displayed on the Sony Screen...
>
> Problems corrected 3 days later by a 2nd superb TWC Tech
> for 'free' were:
>
> Replaced RG-6 pole cable to house with new RG-6 dual
> shielded cable..
Replacing rg6 for an rg6 for nothing except if you have alot of
interference and/or cable was eaten by a squirel
>
> Installed 1 3 way splitter in basement to replace my 2 gold ones...
maques exactly the same thing
____/_____ /
/ / -------------
-3.5db ------- / / /
/ / -7 -7 -7
-7dB -7dB
> Installed 3 RG-6 cable runs... Two to HDTV, 1 to Analog TV
> (They dumped my RG-59 cable basement & bedroom extensions.
>
> On 3 way 'unbalanced' TWC splitters: 1 cable reads +10db at HDTV box,
> the other two Cables are +7 db each
> and are used for Analog HD PIP & other
> Analog bedroom TV... I tagged my
> Best of 3 cables with red tape...
you don't need any reducer and any amp.... if you are using a cable
modem.. Cable modems spec are generally good between -15dbmv and
+15dbmv. Even at -10dbmV it's good. figuring an high tempeture change,
you'll get a variation of max 2dbmv when the temp change of 20'C...
Also, the reducer increase your foward signal. signal that the cable
modem inject on the network to reach the server UBR.. Spec to be for
an analog signal between 0 and 14bdmV to the back of the tv. for
digital signal it's between -15 and +15dbmV for all Scientific atlanta
receiver.
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