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ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
Reviews:
·WOW Internet and..
·Comcast

[Signals] Fluctuating Power Levels Above 590 Mhz

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Hi All-
I've been monitoring my TM822G's power levels ever since I got the new Blast! service. I did not have a D3 modem before that. Noticed that my power levels on the three highest frequencies vary whereas the other channels are pretty constant. They drop at night on a fairly regular schedule. That kind of surprised me because I heard of other peoples signals actually rising at night due to temperature changes.

Normally the SNR on all these channels is 37 or greater but the channels that experience the drop in signal power also have a falling SNR. They bottom out at a SNR of about 32 and then rise back to about 37 as the signal strength increases.

Any ideas on what is causing the changes in strength/SNR? My service has been great...just curious.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
Do you have any old splitters in your drop somewhere?


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
Reviews:
·WOW Internet and..
·Comcast
The line from the pedestal to the outside of my house is about 4 years old. It connects to the house on the outside at a coupler.

I had a history of TV signal problems a couple years ago until I added an Electroline EDA-FT08300 active return amp to the line coming into the house.

Everything including the modem is directly behind the amp. The only thing that seems to change with removing the 3dB amp is that the signals all shift down by 3dB.... a lot more when I add the splits required for the TV sets.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
its a 15db amp, with an 8way.

looks like a suckout, as it only happens at night.
--
I'm better than you!


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
Reviews:
·WOW Internet and..
·Comcast

3 edits
It is a 3dB amp. And read my message, the amp changes nothing with respect to the drops. Just offsets them.

What is suckout and why would only the highest frequencies be affected by it?

»www.electroline.com/fact_sheets/···heet.pdf


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
dude its +15db minus the 8 way so call it 11db of loss, this gives you +4, throw a DC in there for the voice port, and BAM youre at +3db. I know how amps work. and i did read your post, thats why i commented.

a suckout is dip in the frequncy response of the cable. could be cause by improperly prepped hardline, kinks, cracks, etc....in this case i would say either a small crack, or even a bad splice.

odds are around 700mhz it would go back up in strength, so it wouldnt be a complete rolloff, if it was youd see your TV breaking up.

it just depends where on the wavelength this issue it. move it back a little in the cable and it would affect different frequencies.
--
I'm better than you!


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
Reviews:
·WOW Internet and..
·Comcast
reply to ClockerXP
Thank you for the info!

So I guess all I can do is make sure the cable is tight at the ped as well as at the coupler on the outside of my house.

Other part of my question...do I really even care about 2-3 channels when I have 8? I only have Blast! service so it seems 5-6 channels that are 'stable' all the time would be plenty... but I have no idea.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
yes you should, because when there is too much seperation between bonded channels your modem will have issues staying locked.

ideally you want them with a db or 2 of each other.
--
I'm better than you!


flwpwr

@comcast.net
reply to ClockerXP
What are your return levels at this time? I only ask because a suck out would likely loose connection on the upstream by the time you lost what 10 dB on higher freqs? That seems more like something else to me. If your return is hopping up there though that may be different.


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
reply to ClockerXP
My two upstream channels are pretty stable in the 37-40 range. I have a couple more days worth of data, recorded at 2min intervals. I will update this thread in the evening.


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
Reviews:
·WOW Internet and..
·Comcast
Well I was checking all the connections on the outside of my house (at the coupler). They were tight with no obvious signs of degradation.

I decided to go look at the Pedestal in my back yard since it has never been locked and half open all the time, anyway. Saw there were two connections in there so I decided to switch my line to the other one just to see what happens. There was about a 0.2dB drop in power across the channels. I decided to just leave it that way and see what happens and left it. Then something jumped out at me...the unused output was not capped. I always read that it was a good idea to cap unused ports. I had one and added it as shown in the picture above.

I will have to graph out the signals during this time to see if it is just related to the normal fluctuations I have been seeing but it seems adding the cap resulted in about a 1dBmV increase across all downstream channels used by my cable modem.


dmk08809

join:2001-09-08
Clinton, NJ
reply to ClockerXP
Clocker, Impressive graph. What did you use to collect the data and present it this way? Most cable modems apparently don't allow SNMP so I'm curious how you polled for this data.


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
reply to ClockerXP
All done with MS Excel, including data collection from the modem. Look for another thread that I started with a sample Excel file.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

1 recommendation

reply to ClockerXP
Had you added the cap without touching anything else, maybe. But adding that little cap did not add 1db to your power levels. You broke the connection and it re-established, showing slightly different levels, which could be for any number of reasons. SNR would be what it would effect, if at all.

There are hundreds of unterminated tap ports in any given system, just for reference.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
said by beachintech:

There are hundreds of unterminated tap ports in any given system, just for reference.

more likely thousands
--
I'm better than you!


ClockerXP

join:2001-05-24
Sterling Heights, MI
kudos:1
Reviews:
·WOW Internet and..
·Comcast
Click for full size
Well the signals for my 4 (maybe even 5-6) highest frequencies have been all over during the past 5 days as shown in this latest chart. Tonight they are not dropping as much though. You can definitely see a shift in the data at data point 2750 after I added that cap in the pedestal. Of course it could be related to me just disconnecting and reconnecting the wires. But, the highs seem higher and the lows also seem less low as a result of something.