[time-nuts] HP 5071A Electron Multiplier of Cesium Beam Tube

John Miles jmiles at pop.net
Mon Sep 7 23:46:46 UTC 2009

>   > It's an  HP  3048A.  I   have  long  held  vague  ambitions toward
>   > replacing it with a homebrew digital system but it hasn't happened
>   > yet.
>   > john, KE5FX
>   Thanks, John. You have a fortune in first-class equipment!

Thanks -- this stuff is all pretty cheap if you wait by the eBay river long
enough.  It is more important to have an understanding S.O. than a large
equipment budget (the 3048A occupies a 6' rack in what amounts to my living

>   The -105 dBc/Hz at 1Hz looks pretty good. Is that measured  with the
>   internal reference  in the 11848A? Or can it even get down  that low
>   at 1Hz?

The reference was a surplus 5 MHz Wenzel ULN.  It is rated at -115 dBc/Hz at
1 Hz, so was sufficient for these tests.  The 11848A's 10 MHz sources have a
good broadband floor but are not very stable close-in due to their wide
tuning range.

The actual measurement is here fwiw: http://www.thegleam.com/ke5fx/cs.gif

>   If not,  I see from your web site you have a Wenzel  80MHz  ULN. Did
>   you use  that for the reference? If so, did you ever  find  out what
>   was causing  the ~10dB excess noise in the  regenerative  divider...?

I'm waiting until I have faster digital noise analysis capabilities before
tinkering with the regenerative divider any further.  They need a lot of
tweaking to perform at their best, rather than being the plug-and-play
devices that I originally expected.  The results on that page should be
treated as provisional.

-- john, KE5FX

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