[Milsurplus] Shade-Tree Scope Calibration

[jphutch60bj]

Dave -

I like your Idea!

May I suggest suggest a small circuit using MPSA92 as a current limiter 
driving your (zenier and resistor) stack.

Then use 1% resistors in a stack, across the stacked ziner diodes, 
something like this Attached?

Pic cut from my regulated power supply circuit feed by  ~ 340V.

If it makes it through the filters ? Attached file: junk_thoughts.jpg

Hutch

On 10/10/2020 6:53 AM, David Stinson wrote:
> Shade-Tree Scope Calibration at RF.
>
> IMHO, a properly-functioning scope is
> the First member of the "Holy Trinity"
> of test equipment-
> The Scope, The Meter
> and The ZM-11 Bridge, Amen.
>
> But a scope is only as good as the
> calibration and linearity of it's
> vertical amplifiers.  One can use a
> variable voltage supply and see if the
> amplifier agrees with what it says, but
> who's to say the supply is properly cal'ed?
> Improperly calibrated test equipment
> can have you chasing your tail for days.
>
> For checking the scope at DC input,
> perhaps a 300V supply feeding the top
> of a Zener stack, then stepping down the
> stack, checking agreement at each step?
> Can someone recommend a Zener family
> with closer tolerances than most?
>
> Well and good for DC, but how about
> "where the rubber meets the road"
> at RF?  An old vertical amp in a Tek scope
> might be spot-on at DC or 60 Hz, but that's
> no promise of how it behaves at 4 or 7 MC.
>
> So here's the question:  You don't have
> the NIST-certified standards available
> and you aren't going to take a 2nd mortgage
> to get them.  You need to scope a transmitter's
> output and read the PTP voltage so you can
> calculate the true power output in Watts,
> then use that to calibrate a Wattmeter.
> I have three or four Wattmeters around here
> and none of them agree with each other.
> One Drake is connected to a Johnson Viking II
> with AM 270 V PTP output and the meter says
> the carrier is only 45 Watts.... Uhhh, no...
>
> So, if you calibrate your scopes at RF,
> how do you do it?
>
> TNX OM ES 73 DE Dave AB5S
>
>
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