[time-nuts] 35601A as stand-in for 11848A ?

[BriMDavis at aol.com]

Kent,
 
 Thanks for that nice run-down of the differences between 
the two phase noise interface units, that should give me a
good head start on sorting things out.
 
Kent wrote, not necessarily in this order:
>
>The block diagram is hard to read, but there is another one
>in the 3048A Phase Noise Measurement System Reference Manual-
>03048-90002 on pfd pages 296 through 299 (section 5-40) 
>that can be printed out and pasted together. 
>
I was also able to find plenty of online info on the 11848a, 
and already had its' service manual; but I had no luck turning 
up the 35601a equivalent of system block diagram.
 
 I've ordered a hardcopy 35601a manual, when it shows up next
week I'll try to piecemeal scan the block diagram for each
interface at high resolution and post a link here.
 
>
>The High Frequency circuits which contain the input mixers, 
>input switching, diplexers following the mixers, amplifier chain, 
>gain switching, PLL lead-lag filters and other PLL circuitry are 
>almost identical.  
>
That sounds like a good start...
 
>
>What is different is the Analyzer Interface, assembly A4. The 35601A 
>was closely tied to the 3585A spectrum analyzer, using the 350Khz IF 
>out of the analyzer in the low frequency processing circuits.  
>
OK, so the low band path will need an overhaul, or some outboard
processing, to drive the 3561a
 
>
>The 11848A shares many of the same control signal assignments but there 
>are enough differences both in the control signal assignments and other 
>circuits to make the 3048A software unusable with one possible exception.
>  <snip>
>They also changed the LP/HP filter arrangement and signal path 
>switching in the Analyzer Interface of the 11848A which means 
>that the 3048A software will not correctly control the Analyzer 
>Interface and so will not properly drive a 3561A spectrum analyzer. 
>
If the assignments for the supportable subset were close enough, 
I was thinking of running the HPIB controller board output ribbon 
cables through an breakout card to reassign the control bits.
 
 Else, socket the address and data latches on the HPIB controller
card and piggy back a CPLD board pretending to be an 11848a
 
>
>I also recently acquired a 11848A interface and have written
>a small program to control the 11848A (and also the 35601A) 
>over the HPIB bus which allows the various signal paths and 
>filters to be manipulated using a PC.
>
I'd be interested in that control program for experimenting 
with the unit from a PC.
 
( I haven't had the Series 300 fired up for about five years;
when went to dig it out last month, the moving box with the 
HP-HIL keyboard seems to have hidden itself quite well... )
 
 I don't have much time just now to contribute any code of 
substance, but I could poke a stick at it for testing once 
I've tracked down a 3561a.

thanks,
Brian



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