[time-nuts] Any thoughts on best rubidium?
EWKehren at aol.com
EWKehren at aol.com
Mon Sep 26 11:06:06 UTC 2011
Roy
I did have a HP 8566A before replacing it with the 70000 series. Same size
and weight.
Bert Kehren
In a message dated 9/26/2011 6:27:59 A.M. Eastern Daylight Time,
phill.r1 at btinternet.com writes:
Bert
What's your opinion of the "old" HP8568B with its max. frequency range of
1.3 Ghz and its weight of around 100 lbs. - are the more recent
instruments
that much better ?
Roy
--------------------------------------------------
From: <EWKehren at aol.com>
Sent: Sunday, September 25, 2011 10:47 AM
To: <time-nuts at febo.com>
Subject: Re: [time-nuts] Any thoughts on best rubidium?
> If you want low noise in a spectrum analyzer it all comes down to the
> signal quality into the first mixer. Every thing else with today's
> technology
> is down hill.
> Bert Kehren
>
>
> In a message dated 9/25/2011 5:32:31 A.M. Eastern Daylight Time,
> Robert at delien.nl writes:
>
>> One other thing is that some spectrum analyzers aren't really designed
>> for low noise performance. Since the noise floor is often pretty high,
>> the design of the whole RF chain (e.g. spur levels and such) might have
>> assumed that lots of things would be hidden in the grass.
>
> True, it's one of the many selection criterions for selecting the
> instrument that meets your needs.
> I've been looking a the luggable HP series 859x and 856x, preferring the
> latter because they have a PLL YIG whereas the fist uses a free-running
> oscillator. But these machines are old, 80's and 90's, pricey, and not
> really
> THAT good. Add decent range (up to 9GHz to see recent 5.8GHz devices)
and
> a
> tracking generator and before you know it, you'll be paying $6k or more
> for
> a 20 year old instrument.
>
>> If the
>> analyzer is of the recent "bring a band of RF down to an IF, sample and
>> FFT it for fine resolution" architecture, such things as the number of
>> bits in the ADC and the "cleanliness" of the sampling clock might have
>> been chosen based upon doing 1024 point transforms being displayed with
>> 100dB dynamic range (10dB/div and 10 divisions).
>
> Most modern instruments do that, at least to some degree. My R&S goes
> down
> to a RBW of 10Hz by just mixing. Additionally RBWs of 5, 3, 2 and 1Hz
are
> achieve by additional FFT. This instrument dates from 2001, but I don't
> think more recent instruments can achieve a mixing-only RBW of 5Hz or
> below.
>
>> (not to mention the spectrum analyzer actually generating spurious
>> signals. I ran across that one last year and thought I had an
>> interference source, but, no, went back and checked the spec sheet and
>> it said spurious are <-80dBc, and sure enough, there it was at -82 dBc.
>> And stories about the first LO coming back out through the input are
>> legion.)
>
> Gee, I wish I had consulted this group BEFORE buying my instrument. I'm
> happy with it and I don't regret anything, but you could have added a
lot
> more arguments in favor or against…
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