Products > Test Equipment
FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
maxwell3e10:
@rhb, see reply #1994
3e10 is something relevant to this discussion.
rhb:
Sorry, kid, but that's more trouble than you are worth. I'm not going to play "hunt the wumpus" for a message number. In the future, post a link and make sure it works.
The real question is the difference in the response of a 485 at 50 and 1 Meg ohm input impedance to a 50 ohm source impedance, 36 ps rise time, 10 MHz square wave.
Which is which and why?
Also sitting next to me are a 1.5 GHz LeCroy DSO with switchable input impedance and a Tek 11801 with four 20 GHz sampling heads. I have in total 5x 20 GHz sampling heads and 2x 12 GHz sampling heads. Those are *all* 50 ohms input only. If you read the datasheets for serious scopes you will find that above about 500 MHz, the input *must* be 50 ohms. You think maybe there is a reason?
There are a *lot* of PhDs on this forum. I've not observed any that put Dr, Wizard or anything similar in their user name. The normal pattern is initials, name or some combination. Real PhDs don't need to see initials before or after a name to recognize one. The hallmark of a PhD is the tag line from Clint Eastwood's "Magnum Force". "a man's got to know his limitations".
The real ones do, the failures and frauds don't. Knowledge is infinite. Humans are finite. Getting a PhD is about coming to terms with that. And understanding what to do when you don't know.
At least one friend of mine (Stanford SEP 1982) and I agree that it's an expensive luxury, but if you can afford it, a lot of fun. I suspect that I could find quite a few more friends who agree.
As for you, I'm not too sure you could do a decent job of sweeping floors at NIST; so much ego and so little to justify it.
Have Fun (somewhere else)!
Reg
And yeah, I'm not a *nice* guy. I have this unplesaant habit of telling the truth whether people like it or not.
tomato:
--- Quote from: rhb on August 24, 2019, 12:49:04 am ---You seem very busy avoiding identifying and explaining my 485 photos.
--- End quote ---
--- Quote from: maxwell3e10 on August 24, 2019, 12:54:54 am ---@rhb, see reply #1994
--- End quote ---
--- Quote from: rhb on August 24, 2019, 03:50:45 am ---Sorry, kid, but that's more trouble than you are worth. I'm not going to play "hunt the wumpus" for a message number.
--- End quote ---
His reply to your question is in post #1994.
svetlov:
dear DaveR :) ! detailed photos could not find-probably one of the participants of the forum will want to do photos - so far there's only this video
https://www.youtube.com/watch?time_continue=763&v=FaNvHQW_CsQ
rhb:
Here is a photo showing, starting at the bottom, the reflection response for an 50 ohm BNC terminator , 50 ohm thru BNC terminator and the 50 ohm terminator on a tee. Display is 50 mV/div and 500 ps/div.
The scope BW is 20 GHz with an SMA-M to BNC-F cable. What you see in the first horizontal division is the reflection from the BNC-F connector.
Points:
The thru shows a capacitive reflection as does the tee & terminator. I don't have a 1 M ohm BNC termination, so the thru trace is not entirely accurate
The tee & terminator has a lot of ringing in the stub which is not terminated. The spikes on the trailing edge are multiple bounces. The tall ones are the open end of the tee. The short ones are the terminator end of the tee. The geometry doesn't exactly match the way a tee and terminator are used on a scope input, but it's pretty close. To match the geometry better I'd have to use a different cable and that would change the BNC-F to a BNC-M and change the time relationships as well.
From this one may conclude that the BNC terminator has a BW of about 1.5 GHz, the thru about 1 GHz and the tee and terminator about 650 MHz. These are Chinese, but have been tested and bad ones discarded.
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