albertson.chris@gmail.com said:

Ignacio said it was 1 us wide.

I don't have a 5680A to look at, but all the PPS pulses I have looked at are
at least a few volts.  They are easy to see on a scope.  One common setup is
a 5V driver with a 50 ohm series terminator.  That gives a 5V pulse without a
terminator or a 2.5 V pulse if you terminate it with 50 ohms.

The PPS on a TBolt is 10 uSec wide.

I do have a 465.  You should be able to see a 1 uSec PPS.

Here is the recipe I would use:

Use the probe on Channel 1
Ch 1 Volts/Div: 1 V
Vert Mode: CH1

Horiz Display: A lock knobs
Time/Div: 1 uSec
Trigger Mode: Auto

That should give you a horizontal line.
Adjust the Channel 1 Position so the line is a division or two above the
bottom.

Switch the Trigger Mode to Norm
Trigger Coupling to DC
Trigger Source to Norm (or CH1)
Trigger Slope to +
Turn the Trigger Level knob all the way to the right (CW)

Watch the TRIG light (lower right from the Time/Div knob)
It will blink each second when you get the triggering level right.

Now slowly turn the Trigger Level CCW.
When it starts triggering, you have found the top of the pulse.
If you keep going, it will stop triggering when you get to the bottom.
You want half way between top and bottom, but anything that blinks the light
is good enough.

Now turn up the Intensity until you can see the pulse.  It might help to turn
down the room lights.

Now that you can see something, adjust vertical and sweep to show what you
want.

The above assumes a positive pulse.  If you have a negative pulse, you want
the line positioned a few divisions from the top and to trigger on the
negative slope.

If the pulse is way wider than you expect and the level is the same as you
see on AUTO, you are probably triggering on the trailing edge of the pulse.
Flip the Trigger Slope.

--
These are my opinions, not necessarily my employer's.  I hate spam.

On Thu, 05 Jan 2012 01:44:13 -0800, Hal Murray
hmurray@megapathdsl.net wrote:

60MHz is about a 6nS rise time and is easily fast enough to see it.

This is the problem.  With a 1 second repetition rate, the brightness
is going to be very low.

The old ways of viewing such a low repetition rate signal include
using a hood or dark room, special CRT phosphors, photographic film,
MCP (micro channel plate) intensified CRTs, and of course analog
storage and later digital storage.

I think there is something funny about the 1 PPS output on pin 6 from the currently available cheap FE-5680A units. I have three of these units. On one unit, on one occasion, I did observe a logic-level 1 PPS pulse, exactly 1 microsecond wide.  But after a power cycle it never came back, although the unit indicates a locked condition, and is apparently working. The other two units also seem to work (10 MHz output OK, lock OK) but I have never seen a 1 PPS signal on pin 6 from them. My Tek TDS-210 is easily capable of triggering on and displaying a 1 usec pulse.  Is it possible the pulse appears only after a RS-232 command, or after some other special condition?

On 05/01/2012 16:49, David wrote:

I agree, I've seen it in a Tek 7623A with the storage on, it is quite
difficult without it.

Regards,
Ignacio, EB4APL

PD. Just trying to verify this I made some error and let the magic smoke
leave the unit. It is still smelling ...

On Thu, Jan 5, 2012 at 9:46 AM, beale beale@bealecorner.com wrote:

I think the signal is there, it is just very small

I tried again this morning.  On mine the pulse is there but it's very weak.
I can't see it one the scope but I can see the trigger light flash every
second if I work to set it "just right".  I also see an about 0.3V peak to
peak, about 60MHz sine wave.  I can get the scope to trigger and display
the sine wave just fine.  I have to use a 10X scope probe or I load the
signal to "millivolts"

The PPS signal coming from my Oncore GPS is easy to see on my scope and
even on a DMM set to "DC Volts"

The FE-5680's PPS is not usable directly with my counter, I have to amplify
it then set the counter to 10X attenuation then mess with the trigger
setting so it does not see the 60MHz signal.    Maybe I'm lucky that my
scope has a BNC output on the back for the vertical amplifier, so I can
apply a 20MHz low pass filter and about 20X voltage gain.

The documentation I have says pin 6 is "N/C" but it looks like there is a
way to extract a usable PPS but I think I'm going to need and LC filter,
some op amps and a one-shot and a TTL level driver.  My guess is that pin
6 is either some kind of engineering test/diagnostic signal not intended to
use used or the signal is an accident

--

Chris Albertson
Redondo Beach, California

On Thu, 05 Jan 2012 18:54:31 +0100, EB4APL
eb4apl@cembreros.jazztel.es wrote:

I can not imagine using my worn 7603 to see it.  I rebuilt a 7834
analog storage oscilloscope for just that sort of application although
I have a 2230 analog/DSO that I repaired which would be easier to use
for this.  I just checked and in analog mode, my 2230 can display a
1uS/div sweep at a 1 second interval without trace thickening in room
light but it is dim enough that I sure would not want to use it for
other than verfying the pulse is there.

If you use a Tektronix TDS series scope you can set the acquiring to "peak
detect" instead of sample to let the PPS be visible even for long timebase
run. That is: usually, with the trigger set to "normal" and the timebase to
100nS/div or 1uS/div you can see the PPS anyway. If you set the timebase to
100mS/div then you can no longer see the pulse even if the trigger triggers
the scan: setting the acquire to "peak detect" then the pulse returns
visible and you can see the repetition rate.

On Thu, Jan 5, 2012 at 7:17 PM, Chris Albertson
albertson.chris@gmail.comwrote:

The 2230 like I have was the earliest Tektronix oscilloscope with peak
detect that I know of.  Everything after it with some odd exceptions
like the TDS 620 series included peak detect.

I bought and fixed the 2230 instead of a new Rigol just for the peak
detect.  The low end Rigol oscilloscopes have envelope detect but it
is not clear if it includes peak detect when operating in that mode.

On Thu, 5 Jan 2012 19:47:28 +0100, Azelio Boriani
azelio.boriani@screen.it wrote:

I found it,  I used the +15 V of my triple output supply to power the
pin 4, +5 V input.  A 75ACT240 popped up and who knows the health of the
other things.

Wish me luck,
Ignacio, EB4APL

El 05/01/2012 18:54, EB4APL wrote:

Doh!

Hopefully anything directly connected to that 5 volt supply pin can be
replaced if neccessary.

On Thu, 05 Jan 2012 20:37:06 +0100, EB4APL
eb4apl@cembreros.jazztel.es wrote: