[time-nuts] Need some wisdom from the cesium beam tube gurus out there

paul swed paulswedb at gmail.com
Wed Nov 9 19:14:34 EST 2016

Not the expert but as you say the lower oven temp means higher em and visa
Funny you mention no writing in some document or ebay pixs I saw the same
thing a tube with no details. So that now makes 2 instances of no marking.
My non-professional 10 cents put a tube in you know. Set EM to some beam
current level.
Replace using the same temp resistor if it the beam current goes up lower
the oven temp.

On Wed, Nov 9, 2016 at 7:02 PM, Skip Withrow <skip.withrow at gmail.com> wrote:

> Hello Time-Nuts,
> I have been checking out some cesium beam tubes lately and have run into an
> interesting one.  The tube is a standard HP 05061-6077 unit.  There are two
> labels on these tubes, one at the end that has a serial number, and the
> other large label on the side that has the operating information (and the
> serial number).  Problem with this tube is the large label is completely
> BLANK.  It appears that there was never any information on this label.  The
> source that it came from was pretty closely connected to HP, so it could be
> a tube that escaped before testing/characterization.
> The nice thing is that it works!  Using some random nominal resistors for
> the oven temperature I get good beam current.  Changing the electron
> multiplier voltage also dramatically changes the beam current.  I see the 3
> peaks around the on-frequency point quite nicely.
> So, the question is - how do I determine the operating point of the tube
> with no data?  I could fire up a known tube and set the beam current for
> the same value, but how would the oven temperature vs. electron multiplier
> voltage be resolved.  I would think that a lower oven temp and higher EM
> voltage would give the same beam current as a higher oven temp and lower EM
> voltage.
> I'm sure the HP did not do any characterization of the tube until it was
> all buttoned up.  So how did they determine the temperature of the oven?
> Just from the value of the internal thermistor?
> I suspect the answer is what kind of S/N ratio do I want?  If that is the
> case then I would be tempted to run at the lowest oven temp and highest EM
> voltage that gave me a usable signal - for the sake of tube life.
> Any thoughts?
> Thanks,
> Skip Withrow
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