help w/testing oscope looking at variety of signals

I (hobbyist) was trying out the new (to me) oscope ( tek 2236 ) by trying a suggestion of looking at various waveforms from different equipment around the house , clock radio/oscilators/crystals/wall-wart etc.

i decided to crack open the $5 - 49.86 MHz remote control transmitter and sample the 49.86 MHz crystal and i was wondering what i should expect to see ?

it appears to be (in the best viewing case) a 49.86 MHz sine wave about 2.4 volts. i say 49.86 because the DMM displays that as frequency (as does crystal pkg)

however with diff oscope settings and adjustments there appears to be either a simultaneous super-imposed wave just slightly lower amplitude (.3v) and slightly less than sine like , maybe flatter and the peaks a little wider like a squashed sine wave ? then yet another setting i get what appears to be 3 or 4 of the sine waves super imposed all same magnitude with a slight horiz offset (1/10 of 1 graticule division) but they appear to be intertwined and kind of dancing in tight circle where it appears (3d'ish) the waves undulate toward/away (dimmer and brighter while moving appears to move toward ) very slight but perceptable to my eye fairly easily.

is there a typicle way that data is sent with simpl 4 button 49 MHz remote transmitter ? just wondering what i should expect to see when pressing a button.

thanks for any info robb

Reply to
robb
Loading thread data ...

The most important skill in seeing anything clearly on a scope is triggering. This is the mechanism that holds the trace till some recognizable and repeating part of the waveform occurs. If you trigger the sweep from the same place in a repeating wave, all the copies that you see will overlap precisely, and you will have a crisp, stable view.

The two basic modes for the triggering process are Normal and Auto. Normal mode holds the sweep, indefinitely, till the defined trigger conditions are met. Auto mode will hold the sweep for a while, waiting for the trigger conditions to be met, but will time out several times a second, just so you can see where the trace is. I'll bet you have yours set to Auto mode and it is not actually triggering on any part of the observed waveform.

After you have chosen Normal or auto, you have lots of choices as to what a trigger condition is. First you choose its signal source (channel 1 or 2, the power line, or the external trigger input jack). Then you pick a direction, rising or falling. Then you decide if you want the trigger signal to be filtered (some choices might be high frequency noise filtering, video horizontal or vertical frequency ranges or no filter). Then you adjust the trigger level, till it intersects your waveform. I think your scope shows you a little arrow along the right edge of the screen that shows you where the level is set if you choose channel 1 or

2 as the trigger signal source. Fiddling around with the level, and maybe the filter choices you should be able to lock in on almost any repeating waveform.
Reply to
John Popelish

"robb"

** Usually, the output of the transmitter is simply turned on and off with some type of pattern that identifies which button.

Turn your scope to a slow time base ( like 50mS / division) so you can see this pattern.

Usually no direct connection to the device is needed, just make a loop with the probe and earth clip, fit it around the unit and find the best location.

........ Phil

Reply to
Phil Allison

Adding to John's excellent description of triggering: you'll probably want to choose the Low Frequency Reject or "LF Rej" trigger option. There could easily be some 60 Hz (or other) in your signal that can make the trace dance around.

Mark

Reply to
redbelly
[trimmed]
2236 )

appears

49

having read that , i presume that scope quality/value/usefullness is directly proportional to the variety of user selectable triggering options/settings ?

yes, you are correct, in my case p-p auto

i don't know if it shows an arrow , i have not seen one, this scope may not have that feature as i think i read the 2200 series tek scopes were meant for production line type work with fewer user selectable settings and more Auto-magic for "quick use" as opposed to "thorough use".

Thanks John P,

can't wait to play some more and make the brain connection

thanks again for the help and taking time to respond, robb

Reply to
robb

Not proportional, but an otherwise scope with poor sweep trigger response is almost useless. (snip)

(snip)

Sorry, I was thinking of the newer, digital Teks, that have all sorts of test and indicator information superimposed around the edges of the screen.

Reply to
John Popelish

49

and off with

you can see

a loop with

best location.

thanks Phil,

that will be a fun instructive exercise, trying to find the different signals produced by diff buttons by catching or comparing diffs on scope.

hope i am not boring you pros too much.

thanks again for helpful reply, robb

Reply to
robb

playing with tek 2236 and researching more i probably should have gone for a more feature rich series but this suits my hobby budget and want/need. thanks again for help, robb

Reply to
robb

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.