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Can anyone tell me what a cable simulator is?

Hi all,
A few weeks back, while I was away with work, my wife started to have problems with our cable B/B. She tells me that the "Ready" LED would go off and the "Sync" LED would start to flash. Later that day there happened to be an istallation guy doing some work opposite so she called him over.
He metered our connection and told her that the levels were way too high. He then fitted three inline devices between the modem and the incoming coax. Two of them are 15dB attenuators (I'm an electrical engineer so I know what these are!). The 3rd is a "cable simulator.What exactly is this for?

By the way, the day after I got home the modem dropped its connection again so I removed all three devices and we haven't lost our connection since!

Re: Can anyone tell me what a cable simulator is?

Here is a couple of links for you

http://www.freepatentsonline.com/5738525.html

http://gaj.ca/ an inexpensive way for testing cable modems it says.

Re: Can anyone tell me what a cable simulator is?

Quote:

Originally Posted by sparky621 (Post 34636190)

They reduce the digial signal level but not the analogue. (opposite to a equaliser)

You shpoldn't really need attenuators above 6db. Any higher and he should have dropped your levels at the cab.

Re: Can anyone tell me what a cable simulator is?

Thanks for your quick replies.
Sorry, got it the wrong way round. He had fitted 2 off 4dB cable simulators and a 15dB foreward path attenuator.
My Downstream levels do seem very high I must admit:
Downstream Receive Power Level : 22.2 dBmV
Downstream SNR : 26.6 dB

I believe the Upstream is OK though:
Upstream Transmit Power Level : 45.0 dBmV

The modem is a
Ambit ETH/USB Combo Cable Modem (badged NTL Home 200)
Software version : 2.67.1016
Hardware version : 1.15
And yes, I've had it for a while now!

Could it be because my modem is only about 20 feet from the cab?
However, everything seems to have been stable now for at least 2 weeks (hope I'm not speaking too soon!)

Re: Can anyone tell me what a cable simulator is?

downstream is WAY too high that should be lowered or you could start having problem I do know people who had high levels and been okay but it should be between -12 and +12

Re: Can anyone tell me what a cable simulator is?

Quote:

Originally Posted by sparky621 (Post 34636258)

Thanks for your quick replies.
Sorry, got it the wrong way round. He had fitted 2 off 4dB cable simulators and a 15dB foreward path attenuator.
My Downstream levels do seem very high I must admit:
Downstream Receive Power Level : 22.2 dBmV much to high
Downstream SNR : 26.6 dB quite low

I believe the Upstream is OK though:
Upstream Transmit Power Level : 45.0 dBmV

The modem is a
Ambit ETH/USB Combo Cable Modem (badged NTL Home 200)
Software version : 2.67.1016
Hardware version : 1.15
And yes, I've had it for a while now!

Could it be because my modem is only about 20 feet from the cab?
However, everything seems to have been stable now for at least 2 weeks (hope I'm not speaking too soon!)

You need to call Tech Support to get those power levels sorted.

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---------- Post added at 17:19 ---------- Previous post was at 17:18 ----------

Quote:

Originally Posted by darthlinux (Post 34636487)

downstream is WAY too high that should be lowered or you could start having problem I do know people who had high levels and been okay but it should be between -12 and +12

That is on a EX-Telewest connection but he will be on EX-NTL so those figures do not apply.

Re: Can anyone tell me what a cable simulator is?

Quote:

Originally Posted by whydoIneedatech (Post 34636192)

Here is a couple of links for you

http://www.freepatentsonline.com/5738525.html

http://gaj.ca/ an inexpensive way for testing cable modems it says.

Neither are what the chap has had fitted.

Basically its the same size as the normal attenuators or 'jelly beans' as they are known.

The cable signal needs an specific length of cable to travel down before it reaches the characteristics that make it work with the modem. The adjusts the signal on shorter runs so that it works again. Also the antenuators that where fitted will knock the signal level down some.

The signal that travels down the coax is way more complex than you would think. As I recall parts of the signal actually run through the metal shielding.

I was fortunate to be able to go on a training course with the senior network techs which gave a good insight into how it all works.