[time-nuts] A silly question ...

[Dave B]

Many thanks to all the respondents to my question.

Nice to know I can still think some things through in a good way!  ;-)

Re the below..

Yes, I should have said "dual trace" not "dual beam".  "My bad" as some say.

I should know better, having spent some 3 1/2 years of my life as
in-house service serf at Tek here in the UK (Harpenden and Maidenhead)
towards the end of the transition between the venerable "steam driven"
500 series (Valved, or Tubed 'scopes) and the then new-fangled solid
state equipment, I do indeed know how the 465 (and a lot of other Tek
products of that era) work, and it's differences to the true "dual beam"
instruments (such as the 556 and so on.)

Also, as an RF guy, coax run's are always terminated where so needed at
times like this, and trigger points set-up to be as close to the mid
point of the sharpest edge of a clock signal as possible.  (Taking note
of the specification of whatever is producing it, so as not to get hit
by any pulse width jitter that may be a "known feature" etc.)  In this
instance, two sinusiods, so I chose the rising edge, just because ...

Though it is not "needed" to show two signals on screen at the time, it
is a lot easier (on the eye) to compare one signal drifting past another
(known frequency) signal, not relying on the otherwise excellent
graticule for the purpose I need.

In this instance, I'm more interested in the relative frequency between
the two sources, so the mk1 eyeball and trigger set-up is good enough
for my needs.

When the project is eventually deployed, it will be referenced to the
Thunderbolt and generate a sufficiently stable and accurate 20.45 (and
divisions of) MHz clock for other equipment.

But interesting reading none the lest.

Thanks very much again to all respondents.

Much appreciated.

Dave B. (G0WBX)

PS:    I do like the idea of setting up a camera to take a photo of the
'scope every hour or so!  Not practical for many I guess, but it
illustrates the point well.   But the aliasing opportunity I think would
be perhaps too great, in essence being a sampled data system by then.  
Also, one then needs an accurate 1 hour timer!   And so it goes on ;-)


------------------------------------------------------------------------
On 28/09/18 17:00, time-nuts-request at lists.febo.com wrote:
> Subject: Re: [time-nuts] A silly question ...
> Message-ID:
> 	<1538136285.3807422.1523450984.2C16D488 at webmail.messagingengine.com>
> Content-Type: text/plain; charset="utf-8"
>
> On Thu, Sep 27, 2018, at 11:55 AM, Dave B via time-nuts wrote:
>> Triggering a dual beam 'scope (Tek 465) from the TB on Ch1, and having> the output of the OCXO on Ch2, the resulting display on Ch2 of course> drifts in relation to the static waveform on Ch1.  (Both nice
>> sinusoids.)
> The Tek 465 analog cathode ray oscilloscope was/is a very flexible
> instrument. But this flexibility allows you to set up the instrument in
> ways which will not allow this commonly used oscillator comparison
> technique to work correctly. Since you are interested in these
> instruments, here are some details about setting up the instrument for
> such comparisons.
> (1) The Tek 465 is not a dual beam oscilloscope. Dual beam oscilloscopes
>     (such as the Tektronix 556 and 7844) use a special CRT which
>     incorporates two independent electron guns. Each electron gun

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