[time-nuts] Re: HP 5061A - bad cesium beam tube?

[Bob Camp]

Hi

One way to “decide” the who’s right argument is to get a reasonably good
GPS (Trimble NetRS from eBay maybe) that will run off of 10 MHz (yes this 
means a doubler if you have a 5061a). Feed the atomic clock into the input 
on the GPS.Then log the RINEX files for a while (= a month maybe). Send 
them off to NRCan (free) for analysis. 

If you send it in about 3 weeks after the end of the time period, you will get back
a pretty good clock estimate. It’s certainly good enough to tell you how well
your Cs or Rb is doing. With an Rb, you might do pretty well with a week’s 
worth of data. 

Bob

> On Feb 25, 2023, at 5:06 PM, paul swed via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> The shipping is going to be nasty but then you have dealt with that already.
> Frankenstein's beam is 0 and it was a bad tube given to me. The original
> was a option 004 and it was totally dead.
> It gets tricky if you have a RB and the CS. Who is right? If you have a
> gpsdo thats very helpful in understanding which one may be drifting.
> Frankenstein's beam has always been 0. But the 2nd harmonic is 32. I
> actually inserted an amplifier in the beam measuring circuit and could read
> the beam current or leakage. Who knows it was very small and did seem to
> peak. But it does lock and doesn't seem to drift with respect to the other
> Cs. I use a GPSDO to set the 5 MHz. Eliminates the whole double peak
> possible issue.
> Depending on how much you paid. It could be a keeper. Frankenstein was $125
> at a flea market. But the lessons I learned from it have been far more
> valuable/fun.
> Regards
> Paul
> WB8TSL
> 
> On Sat, Feb 25, 2023 at 2:56 PM Matt Huszagh <huszaghmatt at gmail.com> wrote:
> 
>> Chris and Paul, thanks for the notes.
>> 
>> It now locks! It wouldn't last night, but I just tried again and the
>> continuous operation lamp illuminated. Unfortunately, the beam current
>> is now close to 0 and the 2nd harmonic is at about 10.
>> 
>> The 5 MHz signal seems pretty stable relative to the one from my
>> 5065A. It drifts a little back and forth, but not much. I expect this is
>> a symptom of having a low SNR.
>> 
>> Chris, I do have the service manual; I'll take a look at the loop gain
>> adjustment and the -2500V supply.
>> 
>> Still, I'm not thrilled about having a unit with a weak tube. The seller
>> claimed this functioned correctly (from the pictures though I don't
>> think they knew how to test it). If I can get a good discount I'd keep
>> it, but otherwise I may send it back.
>> 
>> Matt
>> 
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