[time-nuts] Any thoughts on best rubidium?

shalimr9 at gmail.com shalimr9 at gmail.com
Mon Sep 26 13:18:59 UTC 2011


There are aftermarket color LCD replacement available for the HP 8566 and HP 8568 analyzers, either as a do-it-yourself kit, or as a turn-key service.

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: EWKehren at aol.com
Sender: time-nuts-bounces at febo.com
Date: Mon, 26 Sep 2011 07:01:36 
To: <time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Any thoughts on best rubidium?

Roy,
for its time it was the best because of the spectral purity of its Osc. The 
 big problem with the unit today is its CRT. Limited life and no 
replacements. As  rare as Cs tubes. If you can live with 1.3 GHz an excellent choice, 
the 22 GHz  version because of source does not have as good 
specifications.Also repairable,  many parts are readily available.
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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