[time-nuts] HP 5071A Electron Multiplier of Cesium Beam Tube
xde-l2g3 at myamail.com
Tue Sep 8 17:20:16 UTC 2009
"John Miles" <jmiles at pop.net> wrote:
> 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 room).
My GF passed away some time ago so I have no problems in that area.
But I'd word it a bit different - my bed happens to be in my lab:)
> 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
Very interesting. Thanks. It is amazing to see how good crystal
oscillators were in the 1980's.
> 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
> john, KE5FX
That's an interesting answer. Can you explain what you mean by
"faster digital noise analysis capabilities"?
The reason this interest me is I'd like to get the low phase noise
of a Wenzel 100MHz ULN, but I understand the price is $1,500 which
is a bit too high.
Some guys at NIST got very good noise performance with a DRO at
10GHz. This is interesting, since MiniCircuits sells inexpensive
low-noise microwave amplifier ic's and mixers. So it might be
possible to get a low noise cavity DRO at 8GHz and use regenerative
dividers to get down to 1GHz (8 / 2^3), then use injection locking
to get down to 10MHz. This could be an inexpensive solution to a
difficult problem. And you have shown you can put 10GHz on FR4, so a
Rogers pcb may not be needed:
So the question is what kind of tweaking is needed to get the best
performance in a regenerative divider, and what kind of equipment is
needed to do it? Then, is perfection really needed in order to beat
the Wenzel ULN? Maybe put up with lower performance in the
beginning, then upgrade later.
BTW, I love your construction techniques. Everything on ground plane
in shielded boxes, such as
One trick I have found that really helps isolate circuit blocks is
to put them on their own small island pcb, which is then soldered to
the main ground plane to hold it in place. Then find the location of
ground connections that give the lowest crosstalk. A brief
description is here.
I need to post some pictures to show how easy it is to mount
descrete components like caps, transistors and ics. Hopefully I may
find the time to do that soon. But this is now my preferred method
of construction, both for convenience and very low crosstalk.
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