Cable Attenuators which size?

[toolzkit]

Hi all,

Can you tell what size attenuators to fit just from my modem signal strengths? as I dont have a clue.

Ambit 250 Signal Levels

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz Downstream
Power 22.8 dBmV
SNR 41.0 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 1 Symbol rate 2560 Ksym/sec
Upstream Frequency 18800000 Hz Upstream
Power 24.0 dBmV

 

[nozzer]

Hi all,

Can you tell what size attenuators to fit just from my modem signal strengths? as I dont have a clue.

Ambit 250 Signal Levels

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz Downstream
Power 22.8 dBmV
SNR 41.0 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 1 Symbol rate 2560 Ksym/sec
Upstream Frequency 18800000 Hz Upstream
Power 24.0 dBmV

Is there a problem with it ?

Both up & down say locked so it would appear to be working ok

 

[gentlex]

Hi all,

Can you tell what size attenuators to fit just from my modem signal strengths? as I dont have a clue.

Ambit 250 Signal Levels

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz Downstream
Power 22.8 dBmV
SNR 41.0 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 1 Symbol rate 2560 Ksym/sec
Upstream Frequency 18800000 Hz Upstream
Power 24.0 dBmV

u will need a -3db and a -6db... then u can try the -3db 1st if that dont work then try the -6db if that still dont work u can combine them together to create -9db

 

[gentlex]

Is there a problem with it ?

Both up & down say locked so it would appear to be working ok

even though it appears to be locked, the signal power levels r dangerously too high and too low which could cause the modem to reboot quite frequently...

 

[toolzkit]

nice one Gentlex cheers bud

 

[MFCGMFC]

pm sent mate

Cheers
MFCGAVMFC

 

[melttc]

u will need a -3db and a -6db... then u can try the -3db 1st if that dont work then try the -6db if that still dont work u can combine them together to create -9db

what do attenuaters actually do mate? very curious as my sons on 20 meg and only ever gets half that at 10 meg so we have put it down to his line?
would this cure his signal?

 

[Jeza]

Hi all,

Can you tell what size attenuators to fit just from my modem signal strengths? as I dont have a clue.

Ambit 250 Signal Levels

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz Downstream
Power 22.8 dBmV
SNR 41.0 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 1 Symbol rate 2560 Ksym/sec
Upstream Frequency 18800000 Hz Upstream
Power 24.0 dBmV

You can get 10dB attenuators, use one of these or use which ever values to make your attenuation upto about 10dB.

This will bring your downstream to +12dB and your upstream to 34dB which is within the tolerances. As it stands your downstream power level is too high.

 

[MFCGMFC]

what do attenuaters actually do mate? very curious as my sons on 20 meg and only ever gets half that at 10 meg so we have put it down to his line?
would this cure his signal?

attenuators decrease the signal mate

Cheers
MFCGAVMFC

 

[Dream Unlocker]

but they dont increase the modem speed thou

 

[toolzkit]

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz
Downstream Power 13.1 dBmV
SNR 42.7 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 2 Symbol rate 2560 Ksym/sec
Upstream Frequency 22200000 Hz
Upstream Power 26.0 dBmV

You can get 10dB attenuators, use one of these or use which ever values to make your attenuation upto about 10dB.

This will bring your downstream to +12dB and your upstream to 34dB which is within the tolerances. As it stands your downstream power level is too high.

as you can see my Downstream Power is now 13.1 dBmV after using a 3db & 6db together, total 9db attenuator.

now do I need to increase my Upstream Power as its only 26.0 dBmV can I increase it? or is that set by the green hubs in the street.....

 

[Jeza]

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz
Downstream Power 13.1 dBmV
SNR 42.7 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 2 Symbol rate 2560 Ksym/sec
Upstream Frequency 22200000 Hz
Upstream Power 26.0 dBmV



as you can see my Downstream Power is now 13.1 dBmV after using a 3db & 6db together, total 9db attenuator.

now do I need to increase my Upstream Power as its only 26.0 dBmV can I increase it? or is that set by the green hubs in the street.....

No your upstream level will be fine. At the end of the day the lower your upstream power level the better, all this means is you have a good connection to the cab in the street etc and your modem isn't having to shout to get your signal back up the cable. If your upstream power level is 55 or above then thats starting to get a bit too high and your liable to start having problems.

Your downstream of +13dB will be ok. Did you use normal attenuators or were they forward path attenators or equalizers or something like that ? The only reason i ask is your upstream power level has increased by 2dB and yet you have added 9dB of attenuation to your line

 

[toolzkit]

your right I used forward path attenators but Im going to fit a15db attenator just to drop the power a bit more.

where Im used to getting 6-8meg Im now getting 10-12meg I dont if its because of the forward path attenators but I will test and let you know.

 

[rawsy]

your right I used forward path attenators but Im going to fit a15db attenator just to drop the power a bit more.

where Im used to getting 6-8meg Im now getting 10-12meg I dont if its because of the forward path attenators but I will test and let you know.

that would be a good idea . idealy you should be looking for around 0db down and about 40 db up to get to around those levels you would need a 20 db attenuator.

 

[Jeza]

your right I used forward path attenators but Im going to fit a15db attenator just to drop the power a bit more.

where Im used to getting 6-8meg Im now getting 10-12meg I dont if its because of the forward path attenators but I will test and let you know.

Having too much or too little signal will affect your speed. I wouldn't put anymore than the 15dB attenuator on your line though as that should be more than enough and your upstream will be fine as it is.

I did wonder that was all because as i said if you used a normal attenuator then it will affect the upstream and downstream levels but in your case what you've used is just fine

 

[rawsy]

these levels dont have to be bang on especially if there isnt a problem so if it aint broke dont fix it.

 

[toolzkit]

Testing my line.

Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 1 Symbol rate 5360537
Downstream Frequency 402750000 Hz
Downstream Power 0.4 dBmV
SNR 42.1 dB

Upstream Channel
Lock Status Locked Modulation QPSK
Channel ID 1 Symbol rate 2560 Ksym/sec
Upstream Frequency 18800000 Hz
Upstream Power 26.0 dBmV

Have just put 24db of forward path attenators on my line plus theres a splitter which is 3db so total is 27db
now my Downstream Power is zero more or less my speedtest results were good.

 

[gentlex]

i am amaze u can use that high of an attenuator and still get good snr reading ... it may of drop ur ds power level but ur uptsream is still qiute low, but hey if its working good dont worry about it

 

[Jeza]

Test on the London server if your going to use Speedtest as i find that Maidenhead server can be quite slow most of the time.

 

[blackmamba]

Your downstream of +13dB will be ok. Did you use normal attenuators or were they forward path attenators or equalizers or something like that ? The only reason i ask is your upstream power level has increased by 2dB and yet you have added 9dB of attenuation to your line

What are the differences between normal attenuators, forward path attenuators and equalizers?

Which one should I get for cable modems? The current power level down is about 20dB, upstream about 32dB
So I'm guessing I need a -9dB attenuator to get it to around the 10dB range.

I've had a quick look on ebay but not sure on which ones to get and where to get some from. Any links would be appreciated please.