[time-nuts] Note on early VNA's

[Jim Sanford]

Jeff:
Was really great to see you yesterday at BreezeShooters!  Hope to see 
you again soon, maybe better yet, chat on the air!
73,
Jim
wb4gcs at amsat.org

On 6/2/2014 6:11 PM, Kmec at aol.com wrote:
> To the learned audience:
>   
> I agree that the 8410 is an excellent place to start to learn  about VNA
> architecture and issues. I, as well, learned the HP 8410, first  as manual
> system, then we did the automation ourselves (Westinghouse was too  cheap to
> buy a "bundled" system) using a 9825 desktop calculator, from the HP  app note
> of "Semi-automated Network Analysis". My education in this regard was
> superb!  My industrious Vietnamese grad student is learning the issues from  my
> 8410 books and he is building a more modern version.
> However, a slight clarification about the early VNA's: They were not YIG
> based, that came later. The classic HP8542A system was a BWO based system
> with  the 8690 Sweeper and a bunch of plug-in drawers that worked with a Signal
>   Multiplexer to yield a 1-18 GHz system. A 5100 based synthesizer was used
> to  lock the harmonic converter to eliminate harmonic "skip" cal errors
> (Brooke  alluded to this) and the whole mess was driven by an HP 1000
> mini-computer and  had a reel to reel tape drive for mass storage! It was huge ( a
> three bay rack)  and cost $250K in 1968 money (a lot today, $1.5 M ??).  I had
> one of these  systems and still have parts of it! I automated my own newer
> 8410 system in 1986  when I started my consulting company and used the 12
> term error model software  pak (HP11863??) in RM Basic on a 9826 computer (big
> step up!). While I do not  recommend this approach for anyone today, the old
> literature provides great  insight into the issues, where the errors come
> from and so on, as HP had figured  all this stuff out. It is a shame that
> shipping to Europe is so high, as a lot  of these systems and components are
> still around (I have six 8410 systems  still !). A mainframe is under $50.00
> and I bought a working 8411A converter for  $20.00 at Dayton this year (dont
> ask why, I guess it was too cheap....).
>    I had just about every variant of this stuff, VLF through 40 GHz.  Man,
> HP engineering was tops in those days!
> Still, I think a very dedicated homebrewer could build his own design for a
>   < 3GHz VNA from adapted "wireless" parts, but I am too lazy for that. I
> much  prefer hacking some proven hardware into what I need.
>   
> 73
> Jeff Kruth
>   
>   
> In a message dated 6/2/2014 5:47:17 P.M. Eastern Daylight Time,
> time-nuts-request at febo.com writes:
>
> Message:  7
> Date: Mon, 02 Jun 2014 14:36:09 -0700
> From: "Richard (Rick) Karlquist"  <richard at karlquist.com>
> To: Discussion of precise time and frequency  measurement
> <time-nuts at febo.com>
> Subject: Re:  [time-nuts] VNA design
> Message-ID:  <538CEE49.6000901 at karlquist.com>
> Content-Type: text/plain;  charset=ISO-8859-1; format=flowed
>
> On 6/2/2014 12:41 PM, Brooke Clarke  wrote:
>> Hi:
>>
>> I started with the HP 8410 and added an  external computer.
>> Since it can be used manually I think it's an  excellent way to learn
>> about VNAs.
>>   http://www.prc68.com/I/MWTE.shtml#NA
>>
> For my last 8 years at  Agilent before retiring in March, I
> was doing advanced R&D on network  analyzers.  The newer
> guys coming up didn't have an intuitive  understanding of
> network analyzer architectures like I did. I
> started  using the 8410 back in 1973 before I even worked
> for HP.  Because of  the modular design, it was like a
> teaching tool that forced you to  understand what was
> going on.  When I mentored the young guys, I  would
> explain to them a lot of principles based on the 8410.
> Modern  network analyzers are too "automatic".
> The 8410 puts modern VNA's into  perspective.  BTW, I used
> to sit next to Dick Lee, who was a member of  the 8410
> design team in 1963 at the dawn of the golden age of
> microwave  instruments based on YIG tuned oscillators
> and step recovery diode  samplers.
>
> As you noted, the architecture was built around the YIG tuned  oscillator
> and certain things were done that way they were because of  that.
>
> Rick Karlquist  N6RK
>
>
>
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