[time-nuts] OT: Power level reference

J. Forster jfor at quik.com
Wed Dec 2 14:19:27 UTC 2009


Not me. I've repaired and calibrated a lot of 7000 stuff for my lab.

That was the point of my earlier posts, where it was asserted that a good
pulse response indicated frequency flatness for power measurement. It does
NOT!

-John

==================

>>In fact, on the Tek 7704 or 7704A (I forget which) there were "No Cost"
>>options of maximally flat frequency response OR best pulse response. OR!
>
> I think you may find the option was best pulse response OR an increased
> 3dB
> frequency of 275 MHz.   The difference is just an matter of adjusting the
> compensation in the vertical amp.   The best pulse response in terms of
> least overshoot etc, also gives a flatter response in the pass band (which
> it should as this is effectively adjusting to give a pure Bessel
> response).
> The higher 3dB frequency version gave considerable overshoot on the pulse
> response, and a "bumpier" pass band.
>
> I was quite surprised to find quite HOW bumpy the pass band can be the
> first
> time I did a check on my 7904 using an SG504.
>
> Dave
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of J. Forster
> Sent: 02 December 2009 01:31
> To: Mike S
> Cc: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] OT: Power level reference
>
> I do. Very well, in fact.  Unless you have swept a scope with a very well
> leveled sine generator, you are only guessing it is flat.
>
> That's WHY Tektronix sells BOTH fast rise Pulse Generators and Leveled
> Sine
> Generators.
>
> In fact, on the Tek 7704 or 7704A (I forget which) there were "No Cost"
> options of maximally flat frequency response OR best pulse response. OR!
>
> -John
>
> ================
>
>
>> At 07:00 PM 12/1/2009, J. Forster wrote...
>>>Scopes tend to have non-flat frequency response. I'd consider a
>>>precision load and something like an HP 3400A True RMS meter for up to
>>>a hunderd MHz or so.
>>
>> You have to know your equipment. I have a Tek 485 350 MHz analog
>> scope, so I'm confident it's flat into VHF (at least beyond 100 MHz).
>> I've verified it exceeds the 350 MHz spec (i.e. < 3 db down @ 350 MHz)
>> with a tunnel diode pulser.
>>
>>
>>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>





More information about the time-nuts mailing list