Troubleshooting with Viavi Channel Check
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- čas přidán 29. 11. 2017
- Threw together a quick video showing the Viavi Channel expert to see what is passing and what is failing. Please let me know if this video helps you out with finding issues in the field or simply just helps you understand what you are looking at.
Channel Check is a live view of what is going on in the downstream. Whereas one check is a test that runs then saves a snapshot that you can look at.
I've learned more in the 11min than I have in 2 wks with spectrum subcontractor watching your video... Thank you 😊
I've been in your shoes as a former contractor. This is why I made the channel. :)
@@thebasiccablechannel7464 thnx for your videos, do you have videos or are you planning explaining about the parameters like what is DQI over time or what is MER ? plc ? not programmable logic controller.
Thank you SO MUCH for the videos. I was a PBX technician for nearly 20 years...when my company went out of business...leaving me to start over again. This led me to Time Warner/Spectrum. While I have a decent grip on plant fundamentals, interpretation of what I am seeing on THIS meter has been troublesome. I appreciate your explanations for what is going on on the meter.
Great video. First look at a Viavi Meter. It's impressive. Thanks.
It did help thanks...
good vids man. you should do a video on how to set up the meter.. I just got the new viavi meter and I have no clue on how to set it up. I do realize that its gonna be specific to your plant but a walk through on how to would be awesome.
Keshawn Johnson - I have not set one up yet myself but most companies set up the meter for you as far as making an account that the files can be uploaded to and setting all of the limits for every minimum and maximum specification for every value. This way the technician understands where a pass and fail lies when testing catv. This is generally done before the meter is handed off to the technician. This is done from the viavi website and is pushed to all of the meters on that network once it is synced to the network.
I have not set one up. They use strata sync to set them up then push the changes to the meter with a update.
Setting the limit plans up properly is one of most important part of these meters.
thanks you
We was told when we first got these they was to work on a feature to add an amplifier for chasing reverse noise like the DSAMS had. Still waiting. Anyone heard if this will ever happen? They are fine at an amp or at a drop going to the house, but other than that these are frustrating.
Would you be able to do a video on using ingress scans on cable for noise ?.
When I add 25db compensation it thinks the levels are failing. Anyway to tell it that it is not a failing level so every channel wont go red?
Hey man we just got these meters at my work. Im a contractor for Comcast. We use these mostly to balance amps, line extenders, and nodes, I have been having problems with the channels not showing up. We balance high and low channels 120 and 3. And out of town we use 2 and 135. Some places we go i run channel check or one check and only get 24-59 or I will see a bunch of "s" channels. I've asked my work for a training or class to understand how to use these new meters but have not gotten any help. Hence why I have came to the internet to see if I could find some help. If you can give me any pointers that would be great. Thanks.
I don't recall seeing "s" channels. You may have to email me an example thebcchannel@gmail.com. I do recall our Viavi meters often times not loading the lower 10 channels or so (2-13 or so). I would have to stop and restart the channel check which is a total pain. It might be a software fix on Viavi's end. I Assume the forward tilt is the cause of the meter ignoring those channels but I am not sure.
Although yours seems like a different scenario. You can save channel plans though for each area. When you get to one area run a full channel check and save it. When you go to the next town do the same. Make sure you switch to the appropriate one for each town as it may help.
Love the Videos, was curious as to why the OFDM's A CWE correctable were failing on my meter and you mentioned something about Cisco labs not finding a solution? I wasn't sure if it was a plant issues or a software glitch.
It has been told to us that it will fail everywhere we check it and that it is normal. Word is that even cable labs has not figured it out yet.
@@thebasiccablechannel7464 I see the same thing in a few business's in Tampa. They all fail that but good otherwise.
Must be nice to submit maintenance tickets for
i just received one too with no clue either. The common practice is here you go now go figure it out.
Negus Thomas the goal of this video is to help you troubleshoot more effectively when your company just hands you a meter and tells you "good luck" like many contractors do.
unfortunately I am an in house employee.
@@thebasiccablechannel7464
and it's good that someone in America is doing this as well as here in Sydney
Mate, we have the same shit going on here in Australia with what we call or
NBN (National Broadband Network) which is our Broadband Wholesaler
for the country
ages ago i used to be a Liney for ISGM (Telstra Contractors)
the boys today don't know what they are doing, they get put through compliance courses and still don't know shit
some don't know
some don't care
but mostly ..... You get guys that don't know shit then they tell the call centre stupid shit like
if a signal is at -20dBmV they just try stuff , the call Centre suggests stupid things like .. Put a 6dB Attenuator on it
See what i mean ?
they literally have no concept of Ohms law, what an Attenuator is or does, What an amplifier is or does and the rest of it.
I've spend years teaching these guys and bit by bit, Just like you... They come around, but it's always a minority that do come around
Call centre people are clueless but hold the tech to randsom to pull off things that he can't do
such as.... Our supported frequencies are 295MHz - 558MHz
so let's say you have a fault on a carrier at 95MHz,
THAT'S NOW OUR CARRIER
but the call centre people are dumb and they want it fixed.
IT'S IMPOSSIBLE for them to do
but the tech has to do it otherwise they won't offsite and pay him.
it looks like in some of the comments you guys have that bullshit happening as well.
Good to see someone over there trying to train the techs properly as well
GOOD ON YA MATE
Mate can you explain more about Docsis, tdr, when is a water present on a drop on channel check...
he did low cant jump high cant swim if theres water it would affect high more
thx
anyway to check upstream MER?
How can you measure the SNR on the meter?
I don't believe so. Generally you'll use MER on your digital carriers to capture issues impacting your digital carriers. The readings in db are very similar outcomes like SNR. The higher the better. Under 35db off tap is generally too low in most cases. Under 33db at equipment is also an indication of an issue with QAM256. Higher modulation rates you would want to yield higher MER to maintain a clean carrier for the improved data rate of the higher modulation (such as OFDM carriers)
The Viavi ONX-620 (FOR SOME STUPID REASON)
Does not have a provision to display SNR (Signal to Noise Ratio)
it's a Telecommunications basic reading and yet they omitted it
we have ICFR, BER, DQI, and all the bells and whistles but still some wanker forgot SNR
so.. it's not there
the bigger question is... What are you trying to derive from SNR
See, if your'e trying to establish how far the noise floor is from the peak,
The engineers at the head end have given you paramaters
LEVEL
MER
PER BER
POST BER
Strictly speaking, if these things are in check then your SNR is going to be good anyway
Because Signal falls into the noise floor when amplitude is not there
and if the noise rises to the level of the signal your BER is going to suffer
so they go hand in hand
Fucking epic to say the least! Thanks so much!!
Alexander Borrero I am glad to hear you like the video. Hope it really does help you figure this meter out to diagnose issues more effectively.
God I miss that meter, we have to use those garbage VeeX meters 🤢🤮
Also, could you break down everything with OFDM and OFDMA and how they work exactly.
What ??? The Entire subject
There's no space for that, google the white paper and read up on it
BER stands for bit error rate. And you're measuring how many bit errors per billion. Like in your reading was 1 bit error per billion. Which is normal. It's bad when you cant fix in post and have more than 1 error. The nine stands for billion
I know I am late to the party, hopefully I get a response! So basically, if you see PRE BER red at 1.9e-8, does the beginning "1" mean there is 1 bit error per billion? If not, which number in that example is the bit error per billion? Constant debate at my job is if we need to submit ticket for PRE errors, corrected in post, on a few channels or just keep rolling? If several channels are failing PRE BER i have been turning over to network. At what point would you say submitting a ticket to net ops is appropriate?
I am looking up these videos to TRULY understand this meter as opposed to just looking for cable loss or ingress, etc.
@matthew-nmbl
@johnhenryhughes5953
YOUR'E BOTH CONFUSED
Now guys, YOU WANT TO LEARN SOMETHING once and for all.... Listen !!
I dont' know you guys so i don't know if you'll turn out to be dickheads or not, I HOPE YOU WON'T
and i hope you don't take anything personally.
Let's not have any bullshit , Since guys don't like being told they are wrong, BUT.. YOU ARE... so Listen up and i'll teach you a few things
FIRSTLY MATTHEW........ YOU'RE WRONG !!!
RE "BER stands for bit error rate"
NO.. its' BIT ERROR RATIO
See.. Let's understand that the industry sometimes fills our head with shit and there are attitudes of "close enough is good enough" well it's not
B.E.R. = Bit Error Ratio
Although i have no doubt that a course taught you that as Bit Error Rate. (and even though NOT COMPLETELY INCORRECT, it's not correct either, it's roughly correct)
B.E.R IS THIS....
It's a Measure of One thing VS Another Thing
so.. What 2 things then ?
Thing 1 - A Predetermined SAMPLE SIZE of the signal is taken
(Let's say this is E-08 , so 100 Million Bits are look at in the Sample)
Thing 2 - Out of that sample size.. HOW MANY ARE IN ERROR
IT'S A RATIO of Shit Bits to Good bits, to put it simply
the thing about Bit Error Rate, gets justified as.... RATE = SPEED and the signal is TRAVELLING AT SPEED
Yeah, but that has nothing to do with Error Checking
so put simply, if you feel more comfortably saying Bit Error Rate, Go ahead
JUST UNDERSTAND AT IT'S FOUNDATION IT'S A RATIO OF 2 THINGS COMPARED TO EACH OTHER
A GOOD THING
VS
A BAD THING
We are comparing a good signal (of a specific bit size)
and deriving the RATIO of Bad bits vs Good Bits
so... BIT ERROR RATIO
the RATIO OF ERROR in a signal
OK,, NOW LET ME START A PART 2 so this doesn't get too long
so SUMMARY
B.E.R. Stands for (Formally) BIT ERROR RATIO
Bit error Rate, Can be used for very loosely and FROM A CERTAIN STANDPOINT is kinda correct,
its' important to not get hung up on this term as being the correct one,
but its' ok to use it
OK Let's go to POST 2
POST 2
@matthew-nmbl
@johnhenryhughes5953
SO Matthew i'm gonna pick on you again for a second just to get through your comment then we'll get on John Henry ok
LOOK AT YOUR COMMENT
RE "Which is normal."
There is no NORMAL
There is WITHIN SPECIFICATION and NOT WITHIN SPECIFICATION.
As a technician get used to not using words like NORMAL, GOOD, BAD.
god knows how many times i've trained techs, they get sent to site, and i ask
"What's going on" and they say
"I've tested the lead in, It looks good"
WHAT A RETARD ANSWER
Now... This tells me a few things about the tech
1. His Technical Knowledge is very low
2. His ability to communicate Technically is very Poor
3. I cannot trust that he knows what he's doing and therefore i can't trust his troubleshooting
(Because, i then come onsite and look at the Lead-In Cable and found that the connector was not terminated properly)
When someone asks "So what's the situation onsite"
a proper answer should look and sound something like this....
"Ok, the reported problem was...... [insert problem on job sheet here],
when i first arrived onsite i found this [insert initial visual inspection and first readings]"
you should say something like
"I spoke to the client gathered some info about the problem adn this and that was stated , i then went to the PCD conducted a one check and found the following
AMPLITUDE = X dB
PRE B.E.R. = [Insert reading here]
POST BER =
MER ="
those are the minimums then you should say
My thoughts are that this is the problem and i'm planning to troubleshoot as follows.
this way you don't show people that your'e a retard,
and even if you're wrong YOU HAD ENOUGH SENSE TO PROVIDE READINGS
RE "The nine stands for billion"
it's not a 9
it's a NEGATIVE 9
DON'T GET LAZY AND UNDERSTAND THE READINGS
Many techs say things like
the level was 12
the BER was 9
12 What ? 12 Chickens...
If people want to call themselves TECHNICIAN then behave like one and learn what you need to know
so... Learn if things are measured in dBuV or dBmV or dBmW or just dB
and learn the differences
Let me start another post to teach you the differences
POST 3
dBmV (deciBel milli Volts)
dBuV (deciBel micro Volts)
dBmW (deciBel milli Watts)
dB (deciBels)
Just a quick explanation on these
dB on it's own means nothing, but when stated this was it is usually referenced to SPL (sound Pressure level) or is used as an arbitrary figure to say something like, the signal was 3dB down (but it is understood what CONTEXT you are speaking in)
as for the others
THEY ARE A RATIO OF ONE THING AGAINST ANOTHER
so dBmV is a ratio of decibels vs 1 milliVolt
that meaning... when the reading is 0dB THE VOLTAGE IN THE SIGNAL IS AT 1 milliVolt
same as dBuV when its' at 0dB it means the Voltage is at 1micro Volt
and dBm or dBmW when at 0dB it means the POWER of the signal is at 1mW
Another useful CONVERSION TO NOTE is......
60dBuV = 0dBmV
so if you have a signal level of 73dBuV that means it's 13dBmV
VERY USEFUL TO KNOW
so
"The nine stands for billion"
IT'S NOT 9 IT'S -9
Because we are not referring to signals above a volt, but Sub Voltage
so... milli and micro pico etc
GO TO POST 4 NOW
@matthew-nmbl
@johnhenryhughes5953
POST 4
let's now pick on John Henry a little but also address your point of 9 vs -9
first point
" If not, which number in that example is the bit error per billion?"
" At what point would you say submitting a ticket to net ops is appropriate? "
SEE.JOHN LIKE MANY TECHS IS FUCKING CONFUSED
AND...
"I am looking up these videos to TRULY understand this meter as opposed to just looking for cable loss or ingress, etc."
WANTS TO JUST UNDERSTAND IT ONCE AND FOR ALL
This is because a lot of people are going around talking about shit that they have no idea about
LET ME ASK A QUESTION
Re John's Question
What does this mean
"1.9e-8"
Ok, Before you answer
WHAT DOES THIS MEAN
"1.0e-8"
ANSWER :
- it's the PRE B.E.R Reading
- the Figure on the LEFT Denotes how many bits are in error
- the figure on the right Denotes
- E Represents "Engineering Notation"
- -8 represents, well.. Lets just call it an 8 for now, ok
10 to the power of 1 = 10
10 to the power of 2 = 100
10 to the power of 3 = 1,000
10 to the power of 4 = 10,000
10 to the power of 5 = 100,000
10 to the power of 6 = 1,000,000 a Million
10 to the power of 7 = 10,000,000
10 to the power of 8 = 100,000,000
10 to the power of 9 = 1,000,000,000
10 to the power of 10 = 10,000,000,000
The figure on the right represents THE SAMPLE SIZE / HOW MANY BITS WERE COUNTED
so...
"1.0e-8" Means
FOR EVERY 100 Million Bits that were counted
1 was found to be in error
I THINK EVERYONE UNDERSTANDS THAT
NOW LET ME FRY YOUR BRAIN A LITTLE
john henry , pay attention
QUESTION......
Why is it 1.0 bits why is it not "1e-8" ?
and matthew this connects to your comment
"Like in your reading was 1 bit error per billion"
NO INCORRECT
ARE YOU FREAKING OUT ?
LET ME EXPLAIN
it says "1.0e-9"
BECAUSE THAT IS THE LARGEST NUMBER THE METER CAN DISPLAY
Not because that's the actual B.E.R.
POINT 1 - Understand that Viavi have determined that if you have any LESS Errors than 1 Error for every Billion The meter basically doesn't give a shit because we have no real benefit (Since we are not in a lab) to know this resolution of reading
I'll go into this a bit more later...
POINT 2
WHY IS IT 1.0
OK let's look at this then... what does this mean
"1.9e-8"
OBVIOUSLY......
1.9 bit IN ERROR when compared to the 100 Million bits counted
GREAT...
BUT HANG ON.....
1.9 BITS IN ERROR ????????
DEFINE A BIT ?
THE SMALLEST Unit of Data Measurement
OK, so HOW CAN YOU THEN HAVE A FRACTIONAL BIT
there is no such thing as Half a bit
so how can you have 1.9 bits
PAY ATTENTION TO THIS AND YOU'LL UNDERSTAND EVERYTHING....
ANSWER : YOU CAN'T
But here is what the meter does actually
it starts at E-09 (if there are no errors )....
it moves to E-08 (if there are no errors )....
it moves to E-07 and so on until
if moves to E-01
Now... if it started at E-09 and got to E-07 and detected 1 error it would display
1.0 E-07
BUT WHAT IF IT DETECTED 374 ERRORS
HOW MANY ERRORS CAN IT DETECT ?
ANSWER, With a resolution of 0.0 (1 digit Resolution) it can detect 9.9 Errors
or.... 10 Errors before it switches to
WATCH THIS
9.9 E-07 ADD 1 MORE BIT IN ERROR TO GET 10 therefore
it can't display it on E-07 anymore so it goes to
1.0 E-6
SIDE POINT i have a spectrum analyzer that doesn't display 1.0 but 1.00
so
1.00E-08
Now... how did 10 turn into 1.0 ??
IT GOT SCALED DOWN
THINK ABOUT DENSITY HERE
THINK ABOUT RATIO
THINK ABOUT ... when the meter scales up or down, it tries to retain THE RATIO
of corrupted bits to good bits THE SAME
but only the representation changes.
so now what if we have 352 bits in Error for every E-07
MY METER that has 2 Digit Resolution would display this
3.52 E-09
SO... WHAT ??????? YOU ASK
How did we go from E-07 to E-09 ?
BECAUSE
RULE 1 - YOU CANNOT HAVE A FRACTIONAL BIT
RULE 2 -
Having 352.0 E-07 which is identical to
35.2 E-08 which is identical to
3.52 E-09 which is identical to
0.352 E-010 which is identical to
and this would be deemed NO Errors since 1 whole bit does not exist in error
YOU GET IT ?
SO WHEN YOU HAVE A READING LIKE
1.9e-08 your meter is saying this
You have 19 bits in error for every E-07
BUT I HAVE SCALED IT DOWN TO THE LOWEST SINGLE WHOLE NUMBER
WITH A FRACTIONAL PART
BUT I HAVE NOT GONE TO ZERO,.... FOR SIMPLICITY SAKE
So understand that 1.9 bits means 19 bits
and 3.52E-08 means 352 bits in error for Every E-06
Because we took 2 steps down to go from 3.52 to 35.2 to 352
so let's now look at your points again
"Like in your reading was 1 bit error per billion."
NO MATTHEW
there are in reality more bits in error
THE METER JUST DOESN'T GIVE A SHIT
" if you see PRE BER red at 1.9e-8, does the beginning "1" mean there is 1 bit error per billion?"
JOHN HENRY....
the Million or billion or whatever IS THE POINT AT WHICH THE METER CHOSE TO STOP FOR IT'S SAMPLE SIZE
it means 1.9 E-08
Means
1.9 bits were found in error
SINCE THAT;S IMPOSSIBLE
IT'S 19 BITS FOUND IN ERROR FOR E-07 (10 Million)
but it's represented for ease and scaled up as 1.9 for Every 100 Million
Any Questions ???
The OFDM carrier uses LDPC for errors and the QAMs use Reed-Solomon error correction. You can't expect the Pre BER to work the same. Post BER is the same though.