[time-nuts] OT favorite signal generator?

[Robert Darlington]

Patrick,
Using a large fixed attenuator should work fine.   I learned the attenuator
trick when dealing with some variable gain amp chips from Analog.  Instead
of varying the gain, they run at some fixed level that produces a clean
output, and vary the attenuation level to prevent non-linear effects and
distortion.  HP might be doing this, then again, maybe not.   Some of my
instruments are very sensitive to input overloading and I just got in the
habit of using a step attenuator between the signal source and the VNA or
spectrum analyzer, or what have you.   It helps to prevent stupid mistakes
that seem to happen at all the wrong times.

As John Miles said, no HP signal generator should produce a distorted output
at low level.  My Tektronix does!

-Bob

On Fri, Jun 19, 2009 at 7:38 AM, <optomatic at rogers.com> wrote:

> Hey Robert
>
> Great tip about the attenuator.
>
> I looked up some models on the internet and some look fairly expensive. I
> know that I will always be injecting low voltage signals, do you think it
> would be wise to buy a cheaper fixed attenuator, let's say 20dB?, and then
> just depend on the variable rate that the signal generator?
>
> Thanks-Patrick
>
>
> Robert Darlington wrote:
>
>> I just bought an HP 3325A synthesizer/function generator that I really
>> like
>> (for some things anyway) in about that price range.   What you get is
>> probably dependent on what YOU need though.  This thing is pretty limited
>> but this particular one has the high voltage option so the output goes up
>> to
>> 40 volts up to 1MHz.   It only goes to 20.99999999 Mhz (at up to 10V I
>> think) but for 99% of what I do that's just fine.  It has a 10MHz external
>> reference which I hook to either an Rb osc or a Thunderbolt depending on
>> what I'm doing.  It's pretty neat to see all the digits match between the
>> 3325A and the 5335A counter.  Of course, that's being clocked by the same
>> oscillator too.
>>
>> Also, I noticed on some signal generators, dropping the output down to a
>> few
>> mV distorts the signal.  What I learned to do was send my signal out at
>> about 1 volt ((RMS or p2p, doesn't matter) and go through a step
>> attenuator
>> to drop it back down so it comes out clean.
>>
>> -Bob, N3XKB
>>
>> On Fri, Jun 19, 2009 at 6:04 AM, Patrick <optomatic at rogers.com> wrote:
>>
>>
>>
>>> Hey everyone
>>>
>>> Sorry for the off topic post. I have received great advice in the past
>>> with items for my little shop and I can't resist to ask again.
>>>
>>> I am thinking about buying a signal generator. I suspect that I will
>>> mostly use it to inject low uV/mV signals into the amplification stages
>>> of the laboratory instruments I service.
>>>
>>> Any feedback you have would be greatly appreciated-Patrick
>>>
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>
>
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