[time-nuts] HP 5065A questions

timeok timeok at timeok.it
Mon Sep 26 01:58:47 EDT 2016

I think that these pages can help you:


   From "time-nuts" time-nuts-bounces at febo.com
   To "time-nuts" time-nuts at febo.com
   Date Sun, 25 Sep 2016 18:42:50 -0700
   Subject [time-nuts] HP 5065A questions
   Hello time-nuts,
   I have recently had the opportunity to play with an HP 5065A rubidium
   standard and have some questions. This unit has been powered down for
   quite a long time, it appears to be almost working. I can see both the
   137Hz and second harmonic signals but they seem very low.

   In the manual (the one from KO4BB.com) in section 3.9 (pg 3-1) there is a
   procedure to apply a 1A current through the TEC until the 2nd harmonic
   comes back (due to cell flooding).

   1. What the heck is rubidium cell flooding, and how does the TEC in the
   5065A fix this problem? None of the -many- rubidium oscillators that I
   have been inside before has a TEC, and I have never seen the subject
   The manual suggests that it may take several weeks at the 1A current to fix
   the problem (normal operation of the 5065A applies .7V across the TEC).

   2. When the coarse oscillator control is swept across 5Mhz (open loop) the
   137Hz ERROR signal swings about +/-8 on the meter. This seems low (and may
   be related to this flooding issue). Just wondering what others have seen
   on their units?

   3. On page 5-15 of the manual it says to adjust A7R29 for a 2nd harmonic
   voltage of 4V at A14(1). In the section on A14 on page 8-61 the table
   states that the normal A14(1) voltage is 8V. So which is it? Granted the
   2nd harmonic won't extinguish the CONTINUOUS light until it falls to less
   than about 1.1V.

   I'm also curious about the level of the 60MHz signal feeding the Rb cell.
   This unit has several volts of RF, which appears to be plenty, but just
   wondering if anyone has any baseline information.

   Also, any hints about the care and feeding of the HP 5065A would be
   welcome. Thanks in advance.

   Skip Withrow
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