On 2020-04-30 15:15, Phil Hobbs wrote:
On 2020-04-30 13:29, Joerg wrote:
On 2020-04-30 10:08, amdx wrote:
On 4/30/2020 11:59 AM, Joerg wrote:
On 2020-04-30 07:31, amdx wrote:
I bought this TDR a few years ago,
I used it on on a long wire on the ground to calculate the
antenna surge impedance, I saw a nice step in the trace, it
worked fine. Now my buddy bought one, and has a square wave
on the scope, but can't get a step in the waveform, with an
open cable on it. So he ask me to take it home and test it.
I can't get it to work either, and now, I can't get mine to
work! Both have a nice square wave output. I put a 12 ft
coax cable on it without any termination, no step. I put a
long (100ft?) coax, that is wound on a spool, I get a
small dot like it is a very short step, but hardly
Ahm, please don't hit me for saying, but you did not
accidentally have the bandwidth limit engaged on the scope
What can I hang on the output that will show a definite
step or any waveform just to show it works. (C, L, LC, RL
Won't work, it has to be a cable.
It a 50 ohm output impedance, I temporarily modified mine
for 500 ohms output for testing a high impedance antenna,
had a step at 50% of the voltage.
Time was my problem, After Jeroen's post I new time was my
error, I first used delayed sweep to expand the edge. That
found the step. Then I triggered properly and just used a 0.2
us time base to see the step. it saw 50 ohms for abut 320ft and
then the open. Joerg, worth asking, but, I fixed that at the
start. Thanks Guys.
Good! I once became very frustrated because a delayed-trigger
setup just didn't show what I was expecting. Until I found out
that the little plastic (!) delayed-trigger clutch inside the
otherwise very expensive Tektronix scope had quietly broken off.
A 485, right?
No, AFAIR it was a Tektronix 2465. To my surprise there was a guy in
Greece who made new knobs and other mechanical parts for these.
Shipping to the US was pricey but afterwards the scope felt great.
That was before 3D printing, he had made molds for all that.
Whenever a client doesn't have a fast analog scope but needs one (and
they usually do) I recommend these. Just not a version with a
digital meter built in because those tend to overheat.
I have a 2467 (350 MHz, microchannel plate CRT) that I use occasionally.