Novice X-Y Problem 2265


Alan Young <agyoung@...>
 

Hello all,
I am trying to use a 2246 for monitoring a two tone input in ch1 and 2 to look at the beat pattern of a transmitter.
When in X-Y mode I don’t see anything. If I push the beam finder I see the two dots all the way to the left and have superimposed them. The test setup is a demodulation signal from the tap to X and the Y is the RF sampler out. The device has a trigger port for triggering, using ch 3 for the trigger. When the transmitter is keyed and beam finder pushed in I can see vertical deviations of the demod signal but no movement in time. Without pushing in the beam finder I see nothing. I haven’t used a scope in 40 years, last one used was a 465.
Any thoughts would be helpful, and thanks in advance.

Alan
N5AGY


Wayne
 

Hi,
I've been away from anything RF for almost 50 years, but I have both 2245A and 2247A scopes and have used the X-Y functions a little bit. I am very well old enough to be rusty at using something I haven't used in a long time, so I fully get where you are coming from.

I am confused by your statement about triggering on chan 3--if you are in XY mode, the scope's sweep generator is turned off and horizontal deflection is provided by the chan 1 input, so triggering is irrelevant--there is nothing to trigger.

Vertical deflection is provided by either chan 2, 3, or 4--I use chan 2 as you did because it has full functionality.

Turn off all of the chan 1-4 pushbuttons above the vertical attenuators--all lights in that row off. Ground the inputs of both chan 1 and chan 2 (both coupling selector lights off), and adjust intensity, chan 1 position, and horiz position for a dot in the center of the screen. Be sure to keep the intensity down so as not to burn your tube. Next, connect your X signal to the chan 1 input and choose AC coupling. Do not push the vertical button for chan1 as you would if making a voltage measurement. Adjust the chan 1 attenuator as necessary to get a horizontal line in the center of the screen. Again, it is important NOT to push the button to turn on channel 1 vertical--chan 1 is going to be your "horizontal sweep". Now connect your second (Y/vertical) signal to the chan 2 input, select AC coupling, and push the CHAN 2 button above the attenuators. Adjust the chan 2 attenuator as necessary. You should now see your X-Y display. Hope this helps!


Alan Young <agyoung@...>
 

Hello and thanks Wayne.
I was using ch3 for the trigger as the sensing device Precise RF SMT Station Monitor has a trigger line out. They really don’t describe how to use it but I agree with you, it isn’t necessary.
I think the problem is with the scope. I can’t deselect all of the MODE buttons at the same time. If there is one remaining selector lit, pushing the deselect button does nothing except flash the vert on lower left and “X-Y” on the lower right. The dot is present, actually two dots, for just a brief second before the relays change. It does this whether any of the channels are the last one selected. I have power cycled it numerous times to no avail.

I hope there is some clarity in what I’ve described!

Thanks again.

Alan


Wayne
 

That does sound like a problem with the scope. There might be some info in the book about the flashing displays but I don’t have time to look into it for a couple of days now. See if you can find anything about what the flashing means. And, it my be something peculiar to the 2246-I only have the s open on either side of that one. Maybe someone else can shed some light.


David Holland
 

What about these settings? (From another one of my old pictures where I
was aligning an IF strip w/ a 2246, IIRC, it was w/ X/Y mode.)

X in Channel 1
Y in Channel 2

DC Coupling for both.

A and B Mode button: X-Y
Vertical Mode button: Channel 2

I wouldn't think triggering would be applicable to X/Y Mode. So the
whole group of Triggering settings on the right have no bearing.

David

On Wed, May 5, 2021 at 3:03 PM Wayne via groups.io <WAYNECL=
AOL.COM@groups.io> wrote:

That does sound like a problem with the scope. There might be some info
in the book about the flashing displays but I don’t have time to look into
it for a couple of days now. See if you can find anything about what the
flashing means. And, it my be something peculiar to the 2246-I only have
the s open on either side of that one. Maybe someone else can shed some
light.






Alan Young <agyoung@...>
 

By flashing I should have said blinks once. I think that is normal behavior as anytime a switch is pushed that will briefly blink an indicator.
I really like the 465 much better than this 2246. This one feels “cheap” and flimsy. (Trying to justify a 465!).

Thanks again.

Alan


Wayne
 

Good clarification--I think you are correct on the single blink, but can't remember for sure.

Actually, you might still be able to get it to work--there may not be a problem here. Since you can't seem to turn everything off in the MODE section, If you just leave chan 2 on, and ground the chan 2 input (both lights off), you should still be able to get a horizontal line if there is a signal on the channel 1 input. If you are feeding the square wave probe compensation ("calibrator") signal into chan 1, the square wave will result in two dots in the horizontal plane, due to the "dwell time" of the signal at the positive and negative portions of the square wave. If you briefly turn up the intensity, you should see a faint line between the dots, representing the rise/fall portions of the square wave. Just put your X and Y signals in as I said in the previous post, and it ought to work if all is OK with the scope.

I understand your "cheap and flimsy" comment after using the 465; I feel the same way, but I have to say I find it very nice to have a much lighter scope to carry around. And both my 2245A and 2247A work very well. And all of them, in my estimation, are nicer to use than the new digital scopes that have one knob with many functions that you are always having to select with push buttons. The older ones are much faster to use, at least for me.


 

Alan,

The 2200-series WERE "cheap and flimsy" compared to the 400-series scopes (well, the knobs and buttons were, at least. The cases were still pretty well made), but that was by design: Tek was facing fierce competition from Japanese manufacturers and they designed the 2200-series scopes to reduce cost of parts and assembly (and, whether intentional, or just a fortuitous side effect, of maintenance). The 2200-series scopes also wound up being much lighter than the 400-series, but I'm not sure that is a cost-cutting measure, or if it was meant as an improvement in user-experience (it certainly is easier to haul a 2235 around than a 465).

The later 2200-series scopes, like the 2246, increased the cost cutting by going to entirely (or mostly) digital controls, but this also allowed the controls to be programmed by GPIB or loaded from saved settings, which was another kind of user-experience improvement, though not one that everybody appreciates in equal measure. Lots of folks, myself included, like solid, direct mechanical controls rather than fly-by-wire instrumentation.

-- Jeff Dutky


-
 

I never considered DSOs and other digitally controlled equipment as
Fly-by-Wire but that's an excellent analogy. Thanks.

On Wed, May 5, 2021 at 8:10 PM Jeff Dutky <jeff.dutky@gmail.com> wrote:

Alan,

The 2200-series WERE "cheap and flimsy" compared to the 400-series scopes
(well, the knobs and buttons were, at least. The cases were still pretty
well made), but that was by design: Tek was facing fierce competition from
Japanese manufacturers and they designed the 2200-series scopes to reduce
cost of parts and assembly (and, whether intentional, or just a fortuitous
side effect, of maintenance). The 2200-series scopes also wound up being
much lighter than the 400-series, but I'm not sure that is a cost-cutting
measure, or if it was meant as an improvement in user-experience (it
certainly is easier to haul a 2235 around than a 465).

The later 2200-series scopes, like the 2246, increased the cost cutting by
going to entirely (or mostly) digital controls, but this also allowed the
controls to be programmed by GPIB or loaded from saved settings, which was
another kind of user-experience improvement, though not one that everybody
appreciates in equal measure. Lots of folks, myself included, like solid,
direct mechanical controls rather than fly-by-wire instrumentation.

-- Jeff Dutky






Alan Young <agyoung@...>
 

It appears that the 2246 has a problem with the X-Y mode. Long story short - each of the two inputs. When viewed individually (or comparatively in AB mode) I can see the demod signal on one channel and the RF envelope on the other, normally. However, when in X-Y mode, only by pushing the beam finder can I see anything. While pressed, it shows bothe the X and Y input only in the vertical mode. I can see each channel, but the respective inputs just modulate in the X (vertical) axis.

I have poured through the manual and nothing helpful. I guess I am looking for another scope. Didn’t pay much for this one, and it is always a gamble. So, I guess I’ll try another one. I don’t need anything esoteric as it will just be looking at RF in the 4mh-50 MHz range. So the search is on.

Thanks to all for the help and information.
Alan