qam differences

[lezwez]

i just wanted to know what the differences are in these qam readings i have seen 64 and 256 qam listings and have seen alot of people talking about them recently i looked on the wiki site about them and it's a bit to techincal for me so could somebody dumb it down for me whats good and bad and what they do.

[Mick Fisher]

All you really want to know is that 256 is a method of getting more efficient use of the existing infrastructure and that Tjets don't like it.

[lezwez]

i looked up tjets only information i get is about paint brushes

[Mick Fisher]

Then try googling "tjet cable modem"

[Cobbydaler]

Originally Posted by lezwez

i looked up tjets only information i get is about paint brushes

A Terajet cable modem...

Used, I believe, in ex Telewest areas.

[Nikesh]

Have a look at this page. Scroll down to Terayon Terajet TJ210.

Originally Posted by Cobbydaler

Used, I believe, in ex Telewest areas.

I'm ex-ntl and I have one, unfortunately lol.

[lezwez]

so im ok then i have a webstar im not sure what i will get next when my new modem aravies hopefull not one of them im in a qam256 area so im lucky i guess i have never had one and have been in a telewest area for many years i used to have the old moto modem not sure which one it was white and turned grey cream color it had the reset button i beleive on the front

Thanks for the information

[Mick Fisher]

As far as I know, Tjets were only on the then Ntl network.

They were a sturdy and reliable modem but since Ntl removed some service (smpt? or similar?) they weren't able to be interrogated. They also could not go above (IIRC) about 8.3Mbps and as already mentioned were completely screwed up by the introduction of QAM256.

[Dark Fiber]

Originally Posted by Mick Fisher

... and as already mentioned were completely screwed up by the introduction of QAM256.

Is it QAM256 per se or the change in power level that accompanies the introduction of QAM256 ?

[Mick Fisher]

Originally Posted by Dark Fiber

Is it QAM256 per se or the change in power level that accompanies the introduction of QAM256 ?

I have no idea and no interest in finding out. All I care about is that teh hardware and services that I pay for and that VM provide work as they should.
I have no doubt that someone will give an explanation if Google can't help.

[Incomplete]

Originally Posted by Mick Fisher

As far as I know, Tjets were only on the then Ntl network.

They were a sturdy and reliable modem but since Ntl removed some service (smpt? or similar?) they weren't able to be interrogated. They also could not go above (IIRC) about 8.3Mbps and as already mentioned were completely screwed up by the introduction of QAM256.

SNMP - Simple Network Management Protocol.

Limitation on them was that the ethernet port on them was only capable of 10Mbps operation.

I remember having one, good modem

---------- Post added at 20:33 ---------- Previous post was at 20:32 ----------

Originally Posted by Dark Fiber

Is it QAM256 per se or the change in power level that accompanies the introduction of QAM256 ?

Power levels at launch were dropped by about 6dB to compensate for the increased loading of the 256QAM constellation. The TJs should have been able to cope with 256QAM but for some reason couldn't get MCNS lock.

[sollp]

Originally Posted by Dark Fiber

Is it QAM256 per se or the change in power level that accompanies the introduction of QAM256 ?

The signal levels increased by about 6dB with the introduction of 256QAM, Not all areas have the 256QAM upgrade, only those that needed it. Was a simple way of increasing data on the Downstream.

No doubt there will be an over the top discussion on whether it be power or signal level and what the difference is.

[Dark Fiber]

Originally Posted by Incomplete

Power levels at launch were dropped by about 6dB to compensate for the increased loading of the 256QAM constellation. The TJs should have been able to cope with 256QAM but for some reason couldn't get MCNS lock.

Thanks for that info