Simple transmission line question

It looks more like 50 ohms. Not perfect, since you don't know an accurate source impedance. Attenuation is less important than termination accuracy, here, provided you can still see what you want to see.

What I'd do is load your source with a known resistor, and calculate the source resistance from the voltage drop, then calculate a suitable pad.

However:

Instead of source termination, use a 450 ohm resistance in series with the coax, at the sending end, and terminate the scope end with 50 ohms. That's effectively a 10:1 probe without reflection. I do that all the time, with

The main application of source termination is where you want to get pulse power down a line into a load that can't be matched, such as measuring trr of a diode.

That assumes that students still read *books*.

Depends how UHF you go. High enough, and fat enough, it starts to think it's waveguide, and you get all sorts of modes happening.

That might actually leave an impression on the student that won't be forgotten. Two lessons in one. That's teaching.

I hadn't spotted that Jim had already suggested this, so I did, too.

He said source, not sauce ;-)

I think George can afford 1%, or better, resistors. Hell, the difference in price is so small that it only matters if you're making millions of units.

I don't know of a development lab that even stocks >1% on 0805 and below. For cheeseparing clients, there is always Monte Carlo (costs extra).

Ever measure diode forward recovery? This is a 1N914. If you put 1.2 volts across it, it forgets to turn on for a couple of ns.

At +2 volts, it turns on a little sooner:

We ran some power diodes at 48 volts forward once, to pump them full of carriers, DSRD (drift step-recovery diode) mode.

(note water hoses on right)

(from an old HP185 training manual)

They do "read"... tweets :-(

One of the most disgusting of things I observe now-a-days... "Family" at dinner in a restaurant. Every family member, parents included, has a "smart" phone in hand, "thumbing" away, even when eating... no conversation :-( ...Jim Thompson

Looks similar in size to LDF6-50.

I used to have an HP180 scope.

I still have one around somewhere. Nasty little things, they were.

I do have an enormous HP185 sampling scope, circa 1960, with plugins up to 4 GHz bandwidth. It was a revelation at the time. The first units used an avalanche transistor in the sampler, and Boff used that to discover the step-recovery diode, which in turn replaced the avalanche transistor.

See the HP Journal of Jan 1960 if you're interested.

As in...

The only problem with that article was its length.

Interesting article. Thanks.

oops colour me clueless.

Depressing. WE have a FAMILY, with many gatherings of the whole 22, with much talking and laughter and hugging. Next up, Mother's Day, at Wild Horse Pass which has a dining room adequate to handle us all. ...Jim Thompson

of

into

reason

soaks

eat

_source_

pulse

reflection

techniques.

It may well be better to leave the problem in the test setup. Most people learn faster from failures than their successes. Think about it.

?-)

Manual stitch bonding is a lost art these days...

"stitch bonding [?stich ?bänd·i?] (engineering) A method of making wire connections between two or more points on an integrated circuit by using impulse welding or heat and pressure while feeding the connecting wire through a hole in the center of the welding electrode." McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright ©

If you put DC into a long unterminated coaxial cable it will store a charge, just like any other capacitor.