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Author Topic: REIN REIN, go to Spain...  (Read 6671 times)

Weaver

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Re: REIN REIN, go to Spain...
« Reply #45 on: June 03, 2018, 01:15:44 AM »

As for the QLN graph, I was assuming that it was the noise that was being frequency-shaped by this, no?

But youíre right, itís very mysterious. Itís as if the noise were going through one path and the signal through another, one that is not experiencing this phenomenon, and then they were getting combined later. You make a very good point indeed.
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boozy

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Re: REIN REIN, go to Spain...
« Reply #46 on: June 03, 2018, 01:49:21 PM »

I've been reading more (thanks burakkucat).  And the thing that sounds most like the problem so far is a split/unbalanced pair (although up until a few weeks ago I had a bridged tap, as well, which may colour my answer).  Sadly I've just added the HG612 recently so don't have Hlog or QLN figures from before.  I scribbled out a rough picture of my line which has at least 9 sections, and was obviously designed post 4 pm on a Friday afternoon - although I'm not sure I remember the end bit correctly but it does go to two cabinets, one for PCP and one for FTTC.  I've read the Broadband boost engineer post...  boy, could use one of those - and he would be able to report back a good result, or what.

There is still REIN between 6pm and 8am, but it was at a different time on Saturday (7pm) - so I'll ask who was working late.  I was totting up the number of security cameras and a big security lights, and I must say they are a paranoid bunch.  Happily none of the lights are on at 6, so I can ignore those.
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boozy

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Re: REIN REIN, go to Spain...
« Reply #47 on: June 06, 2018, 12:16:24 AM »

As everyone was having fun with the reflection maths, I'll give something back.

I'm supplimenting my eldest's Computer Science by teaching her a bit of coding, she won't listen about camel case...  but I've helped her write some code to calculate Bridged Tap/Reflection lengths.  She's being taught VB - but that was a no-no, she's now on a C based language.  It will calculate (well, look up) the lengths for multiple or single minima based on the the number of tones between a number of minima or the single tone with the dip.
The source is attached and is based on aJDSU application note, a compiled version is also there for those without Visual Studio/Mono.

I've also noticed my attainable varies by about 1Mb, so I'm going to restrict the maximum sync rate - and theorise the FECs will drop away.  We'll see.
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burakkucat

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Re: REIN REIN, go to Spain...
« Reply #48 on: June 06, 2018, 12:49:46 AM »

Thank you for the source code. I'll certainly take a look. :)

. . . I'm going to restrict the maximum sync rate - and theorise the FECs will drop away.

Rhetorical question time: What are FECs?
Answer: CRCs that did not happen.
Hint: Do not worry too much about FECs. They show that the error detection and correction mechanism is working well.
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Weaver

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Re: REIN REIN, go to Spain...
« Reply #49 on: June 06, 2018, 03:51:14 AM »

Good for you, teaching something like C#, is it? Well C-like, as you said. VB is pretty shocking. Especially in this day and age.

I'm a huge D lover these days. A lot easier and cleaner than C or C++, very high powered. Garbage collected, but you can turn that off if you really read up on how. Compiled to native code by two superb quality compilers GCC for D (called GDC) and LLVM for D (called LDC, like CLANG) plus the reference compiler from Digital Mars, called DMD, the latter always the latest bleeding edge latest language spec version but not a serious quality code generator, fine for testing or for non speed critical stuff.

Like the C versions, GDC and LDC compilers feature superb intelligent integration with inline assembler, many processors. The DMD compiler has a much inferior and incompatible inline assembler system which I would stay a million miles away from, for too many reasons to list. If you wanted to use assembler then you would be using one of the high performance compilers anyway, so it doesn't make any sense.

Someone has done a Visual Studio component/add-in or whatever that gives the IDE support for D.

You can mix it with C, call C from it, call some C++ from it, call D from C too, in fact there is a compiler switch to help you with the latter because it then warns about features that won't work in an entirely C world without some of the core D RTL and perhaps does one or two more things. It's a feature called something like BetterC.

I think it is hugely cleaned up, all the madness of C++ syntax is gone, the worst things about C are sorted out. There is no preprocessor and no header files, instead there are proper modules and everywhere you wanted to use header files, preprocessor directives and so forth, there are specialised clean tailored features to handle each use case properly. Nothing has been missed. Because there are no header files there is no repeated pulling in and compiling of vast amounts of header file text again and again so compilations are lightning fast in a way that C or C++ can only dream in vain about.

Templates and generic programming are amazing. CTFE, compile-time function evaluation transforms your programming sometimes, occasionally removing huge pieces of code because when it can whole function calls are entirely done at compile-time whenever they possibly logically can be, without limits just because of syntactic restrictions or lack of intelligence on the part of the compiler. I recently had a readonly table with 64k entries that needed complex calculations for each entry. The whole lot was set up by a long involved initialisation routine, but all of that code vanished because it all got done entirely at compile-time and the end result was simply included as readonly preinitialised data.

Hereís me going on and on. Love-struck. Apologies for being so off-topic!

You might be interested anyway. Could be fun.
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boozy

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Re: REIN REIN, go to Spain...
« Reply #50 on: June 06, 2018, 12:56:25 PM »

@Burakkucat, I was interested in the other FEC definition - that itís a bitswap there was no room for (Iíve made that up but thatís how what Iíve read has ended up in my head).  Iíve seen the REIN pattern and am curious if bitswapping would manage it.

@Weaver, I need to work on her hard-coding and explain that when I say ďexactly the sameĒ it means create a function not copy and paste...  but considering she hadnít seen a while loop in school, it wasnít a bad effort.  As for D, Iíll give it a look. I cut my teeth in C and C++, so like a language that allows the shooting of both feet at the same time.  Iíve hated Eclipse since the Sun Netscape alliance days (Iíve literally got the tshirt).
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Weaver

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Re: REIN REIN, go to Spain...
« Reply #51 on: June 06, 2018, 01:59:09 PM »

@boozy well done anyway you are at least teaching her what a while loop is.

You can write C almost 100% in D, the only frequently encountered differences are the missing preprocessor, which I do not miss at all, am very glad it is gone, and the syntax of casts is different, easier to read. Otherwise most of the time it is the same. One other thing is that you do not use zero terminated strings, performance killers always having to scan to the end, or forgetting the zero entirely. Strings are a proper part of the language with a length field. They can be bytes (UTF8), or words (UTF16) or ulongs (UTF32). I always use the latter unless I just want pure ascii, or general random non-text bytes of course. Strings and arrays can be fixed length like C or variable length optionally.

You might find it fun. I would start by reading the "for C programmers" page on the D language (google "dlang" because you can't get google to understand just the letter D) website. Absolutely all of the users are hardcore C or C++ serious programmers and they all know that they want sane conversion from C. A number of users in the very active forum have contributed to the fast evolving design of the language and especially its huge run time libraries, written entirely in D with possible bits of asm or the use of compiler magic directives.

Could be interesting reading anyway.
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boozy

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Re: REIN REIN, go to Spain...
« Reply #52 on: June 07, 2018, 10:54:28 PM »

Failed FEC Experiment - the DLM intervened as well, so there's more than 1 thing changing.  FECs did halve, or more, but I didn't see what I expected on bitswapping.

Code: [Select]
Bearer 0
INP: 57.00 0.00
INPRein: 1.00 0.00
delay: 0 0

Bearer 1
INP: 4.50 0.00
INPRein: 4.50 0.00
delay: 3 0

became
Code: [Select]
Bearer 0
INP          55.00        0.00           
INPRein    1.00          0.00           
Delay          0              0               
Bearer 1
INP          2.00          0.00           
INPRein    2.00          0.00           
Delay           0               0     

Although I'm afraid I have another question.  Can anyone theorise a reason for the difference in the noise disturbance in the 2 QLN graphs (without involving a few feet of copper wire)?
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boozy

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Re: REIN REIN, go to Spain...
« Reply #53 on: June 12, 2018, 09:23:31 PM »

I'm feeling pleased with myself and thanks @burakkucat and @Weaver (and I've had a play with D).  I took the information from burakkucat and worked out what two things together could cause the QLN graph to be like it is, and decided that I must be on a split pair with someone else who has a Bridged Tap.  I've been politely harassing the neighbours, who are quite helpful when I tell them it may help their internet - It turns out that I've found a likely culprit...  I'll be back down there tomorrow to fix it, if it's internal wiring.  If not, OR can do it and the split pair.

I've attached the HLog and bitloading  - and make the Bridged Tap 25.5m. with 2 times that and the distance to the pole would be ~100m which matches up to Weavers calc.  Although I'm not sure that's how it works, as I'm thinking about expansion chambers and standing waves.  It could be interesting if there's another tap of 100m.  However I'll find that out when this one is fixed and my QLN remains sinusoidal or straightens - their internet will improve regardless.
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burakkucat

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Re: REIN REIN, go to Spain...
« Reply #54 on: June 12, 2018, 10:19:35 PM »

That Hlog plot (HLog-2018-06-12-18.44.46.png) definitely shows a bridge tap. I won't attempt to estimate its length just by viewing the image . . .

I remember one case of a bridge tap which was measured to be exactly the distance to the aerial DP. Eventually an Openreach technician climbed the pole, checked the connections and discovered that both pairs of the aerial drop cable had been connected in parallel at the DP.  ::)
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boozy

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Re: REIN REIN, go to Spain...
« Reply #55 on: June 12, 2018, 10:33:42 PM »

I'd probably be remiss if I didn't post the other hlog and qln I've got to see if there's any comments.

And I used the program I helped daughter to write (and have double checked against the graph in the document), so I'd be willing to bet on it - given plus or minus a meter :).  I've fixed the bits that annoyed me too  :-[, I couldn't leave it alone.
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Weaver

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Re: REIN REIN, go to Spain...
« Reply #56 on: June 12, 2018, 11:34:07 PM »

Answer to something the OP brought up a while back, hope this is helpful and sincere apologies if you knew every bit of this already.

When you shift a signal in time by delaying it, then if you take the (continuous) Fourier transform of the delayed thing then you get a function that is a sinusoidal wave pattern in frequency space. (Look up Fourier transform time shift.) Here the idea is that there is a reflection from something in the cable which has an associated time delay and then this results in the sine wave. The Ďwhyí of it can be understood by doing the maths, but also by simply thinking about what is happening. The time delay will have a different effect on the end result which depends on frequency because the reflected wave comes back and mixes with the original signal. Differing frequencies mean that a certain time delay counts as a differing phase shift depending on how many whole cycles at frequency f fit into the delay time. Varying phase difference means reinforcement or cancellation and all points in between when the reflection and original signal mix, and there you have it. Think of older televisions when some fellow in the tv studio is unwise enough to wear a stripy tie or shirt, and what happens if the stripes have a short wavelength. Then there is horrible trouble with ugly spatial interference patterns visible through the camera. This same pattern is seen in different situations again and again.
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boozy

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Re: REIN REIN, go to Spain...
« Reply #57 on: June 15, 2018, 08:24:13 PM »

Found the tap!  The extra line "rung the bell in the shed, but we've taken the bell away".  They can phone and see if they can convince support to send an engineer (it shows no Bridged Tap in the availability checker and a handback of 30).

In the meantime, I've had some fluctuations on my SNR that I'm not sure what to make of...  I also ran a quiet line test, which has never had noise before (or I think it hasn't).  If I bring the phone close when on speaker there's definitely noise.  However, I have cookie bite hearing loss so have no idea of the volume.  If the noise is in a range I can hear: It's fairly quiet.  If not, it could be anything   :-[.

@Weaver, physics homework last night was longitudinal and transverse waves - so it came in useful :) although with a very frustrated child (and parent.
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boozy

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Re: REIN REIN, go to Spain...
« Reply #58 on: June 15, 2018, 10:14:11 PM »

Really confused now. There was a little shower and the SNR dropped again (there was one earlier too, but only for a few minutes).  I decided to force a resync to see what the QLN was like...  The SNR returned to normal.  That would imply that my line was contributing to the noise levels, but I can't see how that would work.  Assuming I have a split pair is this possible, or is there something else?
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Weaver

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Re: REIN REIN, go to Spain...
« Reply #59 on: June 16, 2018, 12:06:04 AM »

@boozy is that GCSE or A-level Physics? Must be nice to have that time with your child though.
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