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Posted by Ed Nielsen on August 5, 2006, 12:21 pm
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Yes, the 5MHz is really critical. As was written by a previous poster,
his return path is 25.35MHz. Mine is 22MHz. If you go to the address
posted by another <192.168.100.1>, you can see what your actual return
path frequency is. But bandwidth is not the only critical factor. Just
as important is the integrity of the shielding. The back needs to be
soldered to the case, not just epoxied (stuck on with glue). If it is
epoxied, signals floating around in the air will disrupt your cable
modem's signals, in addition to possibly causing problems with your TV.
Specs of a splitter should be 5-1000MHz, -110dB RFI/EMI immunity,
Printed circuit board design, Return loss should be upper teens or
above, Isolation should be greater than 25dB. Don't forget solder-backed.
CIAO!
Ed N.
Seguros Catatumbo wrote:
> Is the 5Mhz really critical? When i use the splitter the internet
> connection doesn't even work and the tv quality degrades a lot.
>
> What kind of specs should a splitter have? Is there a way i can measure
> my signal quality? (Maybe some software that is compatible with my
> phillips 7130 tv card?)
>
> Thanks in advance.
>
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Posted by Seguros Catatumbo on August 14, 2006, 7:48 pm
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> Specs of a splitter should be 5-1000MHz, -110dB RFI/EMI immunity,
> Printed circuit board design, Return loss should be upper teens or
> above, Isolation should be greater than 25dB. Don't forget solder-backed.
Damn, i bought one with these specs:
* Model: TSB-21G
* Insertion Loss (In-Out) : 3.5dB Typical
* Return Loss (Output): 28dB Typical
* Isolation (Out-Out): 34dB Typical
* Dimensions: 2.3=CB=9D (L) x 1.9=CB=9D (W) x 0.6=CB=9D(H)
Which exceed the specs you mentioned. But it still doesn't work. The
cable led doesn't light up. How would the cable company give me tv
access if i asked them to?
Can they cripple the signal intentionallly if i only have internet
access or something so i cannot split it without an amplifier?
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Posted by Ed Nielsen on August 15, 2006, 1:08 am
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the line (usually at the tap (or the lockbox in an MDU environment))
which blocks the frequencies from ~50MHz up to the downstream frequency
of the cable modem. Depending on the downstream frequency, there may
also be another filter that blocks frequencies above the datastream.
Amplifiers do no good in that scenario.
Earlier, you had posted levels. Was that without the splitter
installed? If so, what are the numbers with the splitter installed.
What is the quality of the cable you are using to go from the wall to
the splitter? Avoid cables that have push-on connectors like the plague.
That is a very good splitter you bought.
CIAO!
Ed N.
Seguros Catatumbo wrote:
>> Specs of a splitter should be 5-1000MHz, -110dB RFI/EMI immunity,
>> Printed circuit board design, Return loss should be upper teens or
>> above, Isolation should be greater than 25dB. Don't forget solder-backed.
>
> Damn, i bought one with these specs:
>
> * Model: TSB-21G
> * Insertion Loss (In-Out) : 3.5dB Typical
> * Return Loss (Output): 28dB Typical
> * Isolation (Out-Out): 34dB Typical
> * Dimensions: 2.3˝ (L) x 1.9˝ (W) x 0.6˝(H)
>
> Which exceed the specs you mentioned. But it still doesn't work. The
> cable led doesn't light up. How would the cable company give me tv
> access if i asked them to?
>
> Can they cripple the signal intentionallly if i only have internet
> access or something so i cannot split it without an amplifier?
>
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Posted by Timothy Daniels on August 15, 2006, 3:17 am
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> Typically, if a subscriber has internet only, a filter is installed in
> the line (usually at the tap (or the lockbox in an MDU environment))
> which blocks the frequencies from ~50MHz up to the downstream
> frequency of the cable modem. Depending on the downstream
> frequency, there may also be another filter that blocks frequencies
> above the datastream.
> Amplifiers do no good in that scenario.
In 2 western states where I've lived, the cable companies *remove*
a highpass filter if the service is to include Internet in order to allow
the upstream frequencies below 50MHz to pass. That is, they try to
keep the junk that is generated below 50MHz by 20-year old TV sets
and other regional noise out of their system by blocking it with the filter.
It's only when they *have* to allow passage of such frequencies for
Internet service that they remove the filter. Interestingly, a cable company
manager told me that the filter's cutoff frequency varies with geographical
region due to the variance of the ambient noise with region.
*TimDaniels*
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Posted by Ed Nielsen on August 17, 2006, 9:57 am
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everything below ~50MHz, and cable modems need that return path of
5-42MHz to be able to talk to the CMTS), but it was not high-pass
filters to which I was referring. The filters used block from 50MHz up
to the downstream used by the cable modem, which can be anywhere from
50MHz to 860MHz. If there are no analog channels above that datastream
(downstream frequency), then only 1 filter is used. If there are analog
channels above that frequency, a second filter is typically installed
which blocks those channels. Around here, the downstream frequency is
519MHz and there are only a couple of analog channels above that, so a
2nd filter is not used.
If a subscriber does not have HSI but does have digital cable, they
sometimes use a high-pass filter that passes 5-13MHz as most DCTs use a
frequency within that window.
CIAO!
Ed N.
Timothy Daniels wrote:
> "Ed Nielsen" wrote:
>> Typically, if a subscriber has internet only, a filter is installed in
>> the line (usually at the tap (or the lockbox in an MDU environment))
>> which blocks the frequencies from ~50MHz up to the downstream
>> frequency of the cable modem. Depending on the downstream
>> frequency, there may also be another filter that blocks frequencies
>> above the datastream. Amplifiers do no good in that scenario.
>
>
> In 2 western states where I've lived, the cable companies *remove*
> a highpass filter if the service is to include Internet in order to
> allow
> the upstream frequencies below 50MHz to pass. That is, they try to
> keep the junk that is generated below 50MHz by 20-year old TV sets
> and other regional noise out of their system by blocking it with the
> filter.
> It's only when they *have* to allow passage of such frequencies for
> Internet service that they remove the filter. Interestingly, a cable
> company
> manager told me that the filter's cutoff frequency varies with
> geographical
> region due to the variance of the ambient noise with region.
>
> *TimDaniels*
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