I like to put a post-it in the image to remember what it is. If the scope doesn't have readout, the post-it can also note timebase and vertical scaling.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Are you using a scope probe into the 1M scope input??? All you're C'ing is lead ringing. C'ing means you get a C on this project.
idk the phrasing is just a bit ambiguous. Note to self when selling things make return policy unambiguous and clear for even English-speakers with limited skill (unless one likes losing customers.)
Well, you could also do
gates--100r--BNC--50r--------coax------50r scope
But we're talking $18 TDR boards here, not shock-line step generators and 50 GHz scopes.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
The ebay TDR board is shown hanging directly off the scope's BNC input connector.
The ringing is probably ground bounce in the DIP gate, and bad board layout.
Lots of digital scopes ring a bit, too. Some people have no shame.
One could interface to a digital scope, suck out the ugly step waveform, and apply some FIR filter math to make the step perfect.
A modest risetime improvement is possible too.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Is that what is known as a humble-brag? Mikek
I bought the Fast Edge Pulse Generator to find the Characteristic impedance of 253ft of wire laying on the ground. I can do that by adjusting the termination at the far end until I don't have any step in the square wave. Also, with it unterminated, I can find out the VF of the wire, knowing the length. I hope to reduce the VF down to around
0.55 using several coils along the length of the wire. Here is a very short video showing how the wire on ground is directional. The problem, this is about as low in frequency as the antenna goes before losing directionality. I hope with coils inserted in the wire I can reduce the VF making the antenna seem longer. I just wanted to have some measurements as a starting point to see how the characteristics were changing as I made the physical changes. Just having fun. I gave up on the camera, the auto focus, goes through focusing, but then stops at the wrong place. Wife dropped her phone in the water, so I don't have my phone to take any pictures, They may be better.
The Link,
The problem, this is about as low in frequency as the
torsdag den 12. juli 2018 kl. 22.41.23 UTC+2 skrev John Larkin:
the deadbug version has a very similar waveform,
Yes, the bug is called a feature, rightly so. Mikek
Also, when I get the characteristic impedance, properly terminated, I will add an additional ground rod at each end to see if that reduces my ground resistance.
Haha! English is ambiguous by nature, it seems. Saw this adv on TV recently "Huge Car Parking Lot Sale". How many ways can you parse that? :-) Sometimes seems that no one spell & grammer checks scrolling news lines either. Ugh.
English is wonderful. We have maybe as many as a million words, and most of them have multiple meanings. Like "fence" maybe.
I do see tons of grammar and spelling errors online, even from big-name news sites. Print pubs are still pretty good.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
ge to start
see layout
.)
The publishers of printed matter traditionally have proof-readers as part o f their staff. They can be expected to catch 95% of spelling and grammar fa ults.
On-line stuff is easier to correct, and error-detection is less obviously v ital.
-- Bill Sloman, Sydney
e to start
see layout
)
eats shoots and leaves. (describing the diet of a panda)
GH
I have the book!
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
"Zug" in German has well over a dozen meanings as a noun *and* a verb IIRC. The two things that Germans always complained about English when I worked over there some years ago were the large number of words we have for essentially the same thing for which they got by fine with just one or two. The other thing that pissed 'em off is the large number of tenses we have. But both English and German are relatively simple, however, compared to Russian!
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t
I did science Russian and science German as an undergraduate, and didn't se e much difference in difficulty level. The Russian alphabet - Cyrillic scri pt - was an extra complication, and Russian did have more cases, but it's a ll just committing loads of detail to memory.
-- Bill Sloman, Sydney
It does matter if you want to resolve tiny stuff such as connector reflections.
Ringing is nearly all in the layout. If, for example, they used a DIP part it's pretty much game over WRT ringing. Even SO packages won't work well, you'll need DFN and similar packages. Plus a grond plane, controlled impedance traces and super good bypassing. It can be done on a budget but it's a lot of work. I did a low-cost TDR with Here's the TDR unit I bought, click through pictures to see layout
Ouch. Even the resistors are through-hole, meaning they all double as inductors. What you see on the scope is most likely as good as it gets with this layout. If you are mostly concerned with AM band and shortwave spectra it should be alright. VHF, not so much.
-- Regards, Joerg http://www.analogconsultants.com/
edge to start
to see layout
?s.)
?My grammar and spelling both suck. Fortunately, no one's paying me for that. (Spell checkers and such are a big help... as long as they just point out mistakes and don't auto-correct.)
George H.
..."tons"....???
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