VM Modem Signals Levels?

[nibblitz]

Having some occasional issues with my VM Superhub.. Can anybody tell if my Signal Levels are ok, or do they look a little strong & would I benefit from fitting an attenuator?

They are:
Upstream Power: 51.4 dBmV
Downstream Power: -3.3 dBmV
Downstream SNR: 41.5 dB

Thanks for any help...

[TheCoder]

Upstream power is a bit on the high side but I think its still in spec. Thats the 'volume' that your modem 'shouts' back and, as its having to shout quite loud, you definately wouldn't want an attenuator.

If its causing a problem then check your internal wiring (splitters/cabling etc). Try connecting the modem directly to the incoming box (no splitters) and check the level. Ideally it should be around 45dBmV but I think the modems work upto around 58dBmv. If you still have a high level when your internal cables are illiminated then only VM can sort it.

Downstream power is ok. Ideally it needs to be 0dBmv but there's nothing wrong with -3dBmV. It probably means your incoming is 0dBmV and the signal is then being split (splitters cause a 3dB loss).

SNR seems fine.

[rabujas]

you are missing some signals that are very important in a cattv installation.

Most modems lose connection, because of the Upstream Power, when it gets bigger then a value defined by the CMTS (it can be lower or bigger, but normally is 61, the truth is not this one, but it would be 2 geeky to explain what really happends)

that being said, performance problems mostly have to do with CER (codeword error rate). It can be upstream CER or downstream CER. It has a correlations to the SNR (signal to noise ratio) and the modulation being used. You have a very good downstream SNR, and there will be no problem from it (because i dont know of any CATV network using 512QAM modulation). But you dont know the most important part of them all. The signal that is normally the one that goes wrong, "UPSTREAM SNR".

Call you ISP, and as him what is you upstream SNR, and what is the modulation being used on the return path.

Hope it helps

[anaklangsa]

cek signal modem with MDMA .. mobile data monitoring aplications ..

[rabujas]

Actually that new data does not help. What you have there is data transfer statistics, not signals. The only signal you have there is -67dBmv (and it does not say what is measuring).

do not forget that dB's are a logarithmic value. It's kind of ratio. Wont get mutch into it. But check this example.

If you measure the "amount of signal" you have in your equipment it will be between 54 dB's to 78 dB's. And this will be a downstream power reported by your equipment of Downstream rx: -12 to +12 dB's.

So, all signals you have must me correctly identified