Slow speeds - Signal levels?

[ThinkHarder]

Hi,

I am on 10mb and have recently moved house. The NTL dude came round and installed my shiny new 250 modem on the end of the existing cable. He played with his electronic gadgets for a few mins then fitted a 6dB attenuator.

After spending an hour on the phone with NTL to get it from the 2mb it was on because the engineer made a new installation rather than transferring the existing one (grrrr) I ended up on the 20mb trial and it was awesome. Since its gone back down to 10mb though I am getting silly speeds, ranging from next to nothing to about 3mb/s.

Curious as I am I had a look at my power levels.

With attenuator:
Downstream Receive Power Level : -8.6 dBmV to -7.9 dBmV
Downstream SNR : 33.7 dB

Without:
Downstream Receive Power Level : -2.3 dBmV to -1.7 dBmV
Downstream SNR : 33.7 dB

I've read the sticky but I am not quite sure if I am looking at it right so I thought I'd post here and see if they could be causing the problems. From what I understand the levels without the attenuator are better and I have noticed an increase in download speed, but I wanted to check here to see if I am right and to make sure that I'm not making any potential problem worse by doing this. Also if I am right and its ok to do this, why would the engineer fit one in the first place?

Cheers.

[XFS03]

You also have to consider your upstream power levels.

Have you checked those, with & without the attenuator?


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[ThinkHarder]

They don't change, as you would expect as the attenuator only affects downstream.

Upstream transmit Power Level : 51.0 dBmV (Forever and always, only other thing ive seen it on was 49.9 once)

[XFS03]

They don't change, as you would expect as the attenuator only affects downstream.

Upstream transmit Power Level : 51.0 dBmV (Forever and always, only other thing ive seen it on was 49.9 once)
Ah right. When you said attenuator, I assumed you meant a resistive one, which would affect upstream & downstream. He has obviously fitted a forward path attenuator.

When my ntl250 modem was installed, an 8dB forward path equaliser was fitted. I can understand what a normal attenuator or a forward path attenuator does, but not sure about an equaliser.

[Fistynuts]

When my ntl250 modem was installed, an 8dB forward path equaliser was fitted. I can understand what a normal attenuator or a forward path attenuator does, but not sure about an equaliser.

From what I've read, an equaliser ensures that low and high frequencies are received at the same power levels when are delivered to your modem. Attenuators don't attenuate to the same factor across the broadcast spectrum, it seems (low frequencies are diminished more than high freqs).

[XFS03]

From what I've read, an equaliser ensures that low and high frequencies are received at the same power levels when are delivered to your modem. Attenuators don't attenuate to the same factor across the broadcast spectrum, it seems (low frequencies are diminished more than high freqs).Thanks for that.

Just been looking at the manufacturers website (don't know why I didn't look earlier). As you say, the equaliser has a sloping attenuation characteristic, so that the low end of the forward path frequency (85MHz) attenuates more than the upper end (860MHz), to help flatten out the levels reaching the modem.

http://www.technetix.plc.uk/cdrom/products/passives/misc/fld.pdf


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[ThinkHarder]

So can anyone answer my question then please :p: