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Do these figures look ok? (SNR / Power level)

GaryM

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#1
Currently on 10Mb with Virgin using a blue NTL 250 modem.
I have a 2 way splitter on the main cable (balanced 3.5dB), cable box fed from one port with the other port feeding another splitter (balanced 3.7dB). One port feeds another cable box with the other feeding my modem.

Do these figures look ok, taken from the modems log-in page (192.168.100.1 (root/root):

Downstream Receive Power Level : -10.7 dBmV
Downstream SNR : 28.7 dB

Upstream transmit Power Level : 55.8 dBmV

I still get good speeds but do get the odd drop-out especially when using torrents for a prolonged period of time. I have to perform the odd modem reset to get things back to normal.

 
Last edited:

jumpinjo

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#2
Currently on 10Mb with Virgin using a blue NTL 250 modem.
I have a 2 way splitter on the main cable (balanced 3.5dB), cable box fed from one port with the other port feeding another splitter (balanced 3.7dB). One port feeds another cable box with the other feeding my modem.

Do these figures look ok, taken from the modems log-in page (192.168.100.1 (root/root):

Downstream Receive Power Level : -10.7 dBmV
Downstream SNR : 28.7 dB

Upstream transmit Power Level : 55.8 dBmV
iam on tw using splitter and mine is

Downstream Receive Power Level : 6 dBmV
Downstream SNR : 39 dB
Upstream transmit Power Level :44 dBmV
 

mashleylad27

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#4
Im on 10meg ambit200 running Sigma X2 and my readings are thus:

------------------------------------------------------------------------

Downstream Value
Frequency 402750000 Hz Locked
Signal to Noise Ratio 34 dB
Power Level 0 dBmV
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading



Upstream Value
Channel ID 4
Frequency 25584000 Hz Ranged

Power Level 38 dBmV

-----------------------------------------------------------------------------
seem abit mad to me.

so in answer to your question; i aint got a clue.
can any 'know-it-alls' shed some light on this please??
 

loady

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#5
Modems in comparison to a dreambox can operate on very low levells...i have had my modem working with a 12 and 10 db attenuater in unison !!!!
 

thomson

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#6
Modems in comparison to a dreambox can operate on very low levells...i have had my modem working with a 12 and 10 db attenuater in unison !!!!
thats not totally true, depends on the type of modem, for example the surfboard needs a very good signal where'as an ambit doesnt. :)
 

Koevoet

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#8
thats on a sb4200 mate...tried and tested
So you are basically saying you had app. 51db of signal coming into your house , then you attenuated it 22db down as a sb modem needs app. 29db to work properly.

hmmm, i don`t think so

Regards
 

GaryM

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#9
Am I right in thinking that the higher the SNR (dB) the stronger the signal?

Why is SNR measured as a percentage with cable TV and as a dB figure with modems?
 

T4i

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#11
These are mine on a SB5100 (TW)

******************************************
DOWNSTREAM STATUS
******************************************
Tuner Frequency = 331000000 Hz
Carrier Offset = 4 Hz
Symbol rate = 5360537 sym/sec
SNR = 37 dB
QAM Mode = QAM256
Tuner AGC = 0xc4a73380
IF AGC = 0x7af00000
Power Level = -5 dB
QAM = LOCKED
FEC = LOCKED
******************************************

******************************************
UPSTREAM STATUS
******************************************
Upstream Status = UP
Upstream Channel = 3
Upstream Frequency = 29008000 Hz
Upstream Power = 43 dBmV
Ranging SID = 0x1935
Upstream Symbol Rate = 2560000 sym/sec
******************************************
 

GaryM

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#12
It seems my figures are right on the borderline of acceptable, if not slightly over the borderline.
They may well be fine with just the modem connected so its probably down to the two splitters I'm using but seeing as I don't subscribe to cable TV I can't justify an investigation.

[EDIT]

Figures with no splitters at all, just cable modem connected to incoming feed:


Downstream Receive Power Level : 0.1 dBmV
Downstream SNR : 30.1 dB
Upstream transmit Power Level : 50.5 dBmV

Figures with 2 splitters in circuit:

Downstream Receive Power Level : -10.5 dBmV
Downstream SNR : 28.6 dB
Upstream transmit Power Level : 58.8 dBmV
 
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loady

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#13
So you are basically saying you had app. 51db of signal coming into your house , then you attenuated it 22db down as a sb modem needs app. 29db to work properly.

hmmm, i don`t think so

Want me to film it for you ??...i can....seeing as i know that at the time i was right at the top of the peg board in the green box becasue my friend put me there....i was experimenting with my old dbox2 and was under the impression at the time that if i put attenuaters on the modem it would throw signal back down the pipe to the dbox2...i know different now...and the box turned out to be faulty...but thats what i did and i got connectivity....you said that a modem needs 29db to work PROPERLY...you did not say i noticed AT ALL....im not in the habit of telling porkys.....so there...ner ner ner ner ner.

PS...i used to get quite nasty shocks from my cable...seeing as its only a signal...work that out.

regards.
 
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T4i

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#14
I get shocks from mine too, best one is if i stick my head round the back of our TV and I touch the cable feed whilst the DAB radio aerial is near my melon.

OUCH! zap zap zap zap
 

loady

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#15
he he he........ mines worse if my arm touches the stb whilst i got my finger over the end.....fek..my eyes bug out of my head
 

Koevoet

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#16
The problem with the shocks on the coax , could be from the amplifiers not being set up correctly on the DP`s and have power going through a distribution leg , or the network hasn`t been grounded properly.

Regards

@ loady , if possable if you still have those high levels could you post a screenshot of your signal tab .

Regards