Pockethernet Forum

Pockethernet Hardware => Issues => Topic started by: snowmanjax on November 06, 2016, 12:52:53 AM

Title: TDR Calibration
Post by: snowmanjax on November 06, 2016, 12:52:53 AM
Hello all! This is my first Pockethernet, and love the feature set for the price. Everything is working for me except TDR. I've already read the post about the long cables and TDR never reporting back, and having to reboot the PE. I'm sure devs are working their tails off. :D

But I've got another issue, which leads to the forum post topic.

Is anyone else having issues with TDR calibration? I press measure, wait for the measurement, then set the sliders to close to 20 feet (that is the length of the cable I have). The numbers for each pair change when I measure next. And the numbers are WAY off. 16ft on one pair, 23ft another, 21ft the next, and so on.  Happens every time I try to calibrate. They never stay the same number. I've measured the cable to 20 feet, and maybe 1/8 inch. Is that 1/8 inch messing me up, or am I doing something completely wrong?

I've tried calibrating with both ends on, and even snipped off one end to see if it makes a difference. Unfortunately, it does not. I've also used a Cat6 premade 20 foot cable, to see if crosstalk is messing up the TDR, and still get the same results.

If it's just me, then someone PLEASE tell me what I'm doing wrong. If it isn't, then maybe I got a defective unit?

Any and all questions and comments welcome.  :)

Title: Re: TDR Calibration
Post by: jrosado on April 06, 2017, 08:36:09 PM
I have the same issue here.  All calibration measurements are different and when I re-measure they come up with new numbers.  However, those numbers are pretty close to the length of the cable being tested which is 25 feet but when I run the actual TDR test it shows Open@2m which is way off.

Is any moderator reading this?  Do I have a deffective unit?
Should I create a new post?
Title: Re: TDR Calibration
Post by: EvilGenius on April 07, 2017, 04:33:56 AM
Be patient guys, jboxtel will be in here soon enough to let you know what's going on.  They've been working on getting a new batch of hardware ready for sale so haven't had much time to get in here and follow up new topics.
Title: Re: TDR Calibration
Post by: hcjake on June 14, 2017, 09:59:55 PM
I'm having the same issues with TDR and calibration. I get different numbers on the calibration page than I do on the TDR test and neither are accurate. Even after adjusting the calibration, running the TDR test isn't showing proper distance.
Title: Re: TDR Calibration
Post by: spiderweb1967 on September 07, 2017, 05:47:11 PM
  I'm new to this tester seems amazing as to what it can do and was wondering, the TDR Calibration is that done once and then it should be fine or does it have to be done for different cable manufacturers? Solid copper or CCA make a difference? 
Title: Re: TDR Calibration
Post by: spiderweb1967 on September 07, 2017, 07:16:36 PM
Looks like it does not matter how many times you run the calibration sometimes its real close and sometimes it off quite a bit and not very consistent. I realize this is a product that is still being tweaked and look forward to future add ons as well as polishing the current features. 
Title: Re: TDR Calibration
Post by: mercules on October 05, 2017, 11:27:11 AM
Yep exactly what ive been seeing guys!
Title: Re: TDR Calibration
Post by: spiderweb1967 on November 17, 2017, 12:36:46 AM
  Looks like there aren't any TDR Calibration updates yet anyone else waiting for this issue to get resolved?
Title: Re: TDR Calibration
Post by: JP on November 18, 2017, 03:55:31 PM
Note that I see this "problem" only occasionally - note that TDR is not brilliant - it will be fooled (and results get skewed) by things like...

- multiple patch cables/jacks in the length of the wire
typically there is Pockethernet > patch cable > patch panel (jack) > solid CAT5/6 wire > wall plate (jack) > possible another patch cable
...sometimes there are more than one jack in a run (someone messed up, extended a run, etc.)

- not solid copper CAT5/6 wire
...could be stranded wire, could be CCA wire (for a description of CCA see: https://www.computercablestore.com/what-cca-wire-can-do-to-your-network which is a thing you have to watch out for on Amazon and other places, if it's too cheap, it's CCA)

- CAT6 jacks used on CAT5e lines
...or vise versa

- CAT5/6 wire run over/along noisy things
...florescent lights, step-down transformers, fire alarm (red) wire, audio/speaker lines, in the same conduit as AC wire, etc.

- CAT5/6 "repaired" or extended by an electrician
...wire nuts or Telco style (jelly) IDC connectors

For me, TDR is more of a "best guess" it can get me near-er a problem, so I don't have to inspect the entire length of a wire.