Oscilloscope for DCS and other signals for a beginner

That is a SERIOUS scope! I’m sure it will serve you well.

For myself when the scope arrives, and others following, here is Adrian!’s post explaining the filter to eliminate 60 Hz and the details of how to set the scope for showing DCS signal, excellent hand-holding for “the rest of us.”

Viewing the DCS Spread-Spectrum (CDMA) Track Signal

A good place to practice on would be an old radio, especially tube type. Many different amplitudes and frequencies there plus they are continuous. DCS signals will be pulsed and a bit harder to trigger on. With the radio you won’t have keep hitting buttons on your hand held.

Two buttons you will find handy are “Auto” to get the sweep on screen with amplitude and frequency in a range easily observable and “Measure” that will tell you what the amplitude and frequency is without having to count screen graduations.

Have fun.

Pete

Ha! I'm plenty old to have such a radio, but unfortunately don't.  Hopefully their educational modules will suggest some alternatives :-)

My dad was an EE and knew his way around a scope.  One day in the mid-'90s we decided to use one to analyze the DC going from then-newfangled "electronic E-units" to the can motors that were beginning to take over O gauge.  This was all before command control, speed control, etc.  Even so, we discovered some interesting things.

I believe the E-unit in the K-Line steam loco (the one derived from Marx tooling) was designed by, or with input from TCA past president Al Ruocchio.  It produced a PWM-like waveform with well-controlled amplitude.  We also looked at the output of a Starr-Tec Hogger, which was (for the time) a high-end, high-capacity walkaround DC throttle.  Sadly a lot of my Dad's equipment got ruined in a basement flood.  I never learned how to work a 'scope well enough to warrant spending money on one of my own.  Great topic, I hope you have fun with yours!  If you find anything interesting, please post up some waveforms!

@Norton posted:

A good place to practice on would be an old radio, especially tube type. Many different amplitudes and frequencies there plus they are continuous. DCS signals will be pulsed and a bit harder to trigger on. With the radio you won’t have keep hitting buttons on your hand held.

Two buttons you will find handy are “Auto” to get the sweep on screen with amplitude and frequency in a range easily observable and “Measure” that will tell you what the amplitude and frequency is without having to count screen graduations.

Have fun.

Pete

Are you nuts?  I’ve repaired many tube type radios and if you don’t know what you are doing you could blow your scope (a specially if you don’t have a isolation transformer) and there’s hundreds of volts powering those tubes that could kill if you slip with the probe.  I don’t recommend starting out with a tube radio.

@Ted S posted:

...snip... We also looked at the output of a Starr-Tec Hogger, which was (for the time) a high-end, high-capacity walkaround DC throttle. ...snip...

Do you still have any of that data? A friend uses them exclusively on his HO layout and I plan on using one on my proposed O two-rail setup. We would be interested in the results of your research.

@superwarp1 posted:

I don’t recommend starting out with a tube radio.

Especially the old ones that  had the neutral tied to the chassis, and a non-polarized 2-wire plug!  Where is UL when you really need them!

@superwarp1 posted:

Are you nuts?  I’ve repaired many tube type radios and if you don’t know what you are doing you could blow your scope (a specially if you don’t have a isolation transformer) and there’s hundreds of volts powering those tubes that could kill if you slip with the probe.  I don’t recommend starting out with a tube radio.

Seriously Gary? Typical plate voltages run around 500 volts. The scope in question displays 10v/div with ten divisions is 100 volts. Use a 10x probe and you can measure 1000v. This is radio, no CRT anodes and flyback transformers. On a floating chassis use two channels added in minus mode to simulate a differential probe.  You kids need to go back to school.

Pete

@Norton posted:

You kids need to go back to school.

Please...   I know how to use the 'scope, but for some old radios, I'd be somewhat circumspect about fooling around inside as I mentioned.  Besides, since you're not likely to be working on tube radios, why not do some scoping on the many electronic boards we have on our model trains, that's practical experience that you may actually use.

@Norton posted:

Seriously Gary? Typical plate voltages run around 500 volts. The scope in question displays 10v/div with ten divisions is 100 volts. Use a 10x probe and you can measure 1000v. This is radio, no CRT anodes and flyback transformers. On a floating chassis use two channels added in minus mode to simulate a differential probe.  You kids need to go back to school.

Pete

Let’s see an all American 5 radio powered directly from line voltage, no transformer,  depending on which way it’s plugged in the chassis(no polarized plugs here) could be hot, you have a 50/50 chance, connect the ground of that scope to the chassis and watch the sparks fly. Hate to see him ruin  a expensive scope.

@superwarp1 posted:

Let’s see an all American 5 radio powered directly from line voltage, no transformer,  depending on which way it’s plugged in the chassis could be hot, you have a 50/50 chance, connect the ground of that scope to the chassis and watch the sparks fly.  Now who needs to back to school

I understand differential scopes are not common anymore but you can simulate them buy using a second channel as the ground reference. You don’t have to connect scope ground to chassis ground and would avoid it in cases like this.

Just so we make this train related, You use the same technique to test RCMC and later Legacy if you don’t want to blow the board up. Signal ground and chassis ground are not the same.

Pete

Agreed.  I only get the hand me down Chinese scopes from work. I’m kind of jealous. I haven’t played with a textronics since my previous job.

@PRRMP54 This was the '90s, long before smartphones or digital cameras.  My dad's scope was even older, probably from the 1960s, and as far as I know, didn't have the ability to capture or store waveforms.  So my "data" consisted of handwritten notes in a bound copybook, and maybe crude sketches?  I must have at least two dozen of those copybooks.  Unfortunately most of them aren't dated.

What I do remember is that the Hogger ran my postwar Lionels ran very smoothly.  It didn't do anything to improve the performance of what were then-current production Lionels: train set 4-4-2's, 2-6-4's and diesels with the walnut-sized can motors in the trucks.  Chopping a waveform that's already being chopped, and then feeding it to a cut-rate 3-pole motor geared for 200 mph isn't a recipe for scale operation!

Before I could afford digital 'scopes, I used to take pictures of the screen when I wanted a capture.

Great interchange of ideas, guys.  This will compete with other priorities, so keep on poking, it will keep my curiosity where it needs to be to figure this out.  I’m guessing it may help me figure out signal problems with older PS2 locos at certain points on certain TIU channels’ blocks, and answer questions about TIU channel aging, but mostly it’s just interesting.  The multi-track passenger terminal is a likely candidate.  At $500+ this scope is not cheap, but it’s less than some of those nice diesels that periodically come to the front porch, and looks like a much better learning tool for a novice user.  For sure will post when I get a screen to photograph.

Welcome to the digital age. You can save screen shots to a USB drive. No camera required.

Pete