[time-nuts] HP 5065 Rb update

[Bob kb8tq]

Hi

Crazy as it seems, running at a higher C Field current makes the device 
more sensitive to stray mag field. If you want to “soup up” your 5065,
you would adjust the synthesizer for minimum (but still in range) C Field
current. 

Why not go to zero ( or real close to it) ? There are multiple quantum 
“resonance” modes. At zero C field they get very close to each other.
Locking to the “right one” becomes tough. 

Bob

> On Dec 5, 2020, at 3:09 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> Hello to the group.
> Did switch the leads and no major effect.
> I also did provide a separate power supply and am controlling the cfield
> with that. It appears that by going to 7 ma the system is stable on the
> original tube marking of 8714 on the thumbwheel. The original cfield range
> went up to 6.6 ma. Literally adjusting the current resistor in the cfield
> regulator will put it back into range. But thats still easily a 4ma jump to
> get it back to normal.
> Ed to your comment the pot could be expanded though with readings I am
> getting may be just fine. It seems to be approx 5.0 E-12. Its a simple 1K
> pot with digital dial readout that feeds a diff transistor and driver
> transistor. Quite simple.
> That said with the external supply sort of slapped in at 7.28 ma the unit
> is 5.6 E-10. Clearly not stable but the supply is a tek unit etc. I at
> least now know the range the cfield might want.
> *But does it matter that I use a different thumbwheel setting if the
> results are solid*?
> Regards
> Paul
> WB8TSL
> 
> On Sat, Dec 5, 2020 at 2:41 PM ed breya <eb at telight.com> wrote:
> 
>> If the only problem is that you're at the resolution limit of the pot,
>> you may be able to slightly modify the circuit, reducing the pot's
>> effect, but also reducing the total adjustment range. I don't recall
>> what the circuit looks like, but from the discussion I'm guessing it's
>> like a 10 kilohm or so ten-turn WW with a kilodial on it, and it adds
>> some adjustable current to the C-field network. The few k ohm range pots
>> have set-ability that's near the small tick dial resolution. If the pot
>> is quite low resistance, like less than 2 k, it can be much worse, due
>> to the larger resistance wire - the wiper can only interpolate so much
>> between the discrete wire turns, so the net value has more ripple with
>> rotation. If the pot is in the few k region, you can gain quite a bit of
>> actual resolution by upping it to say 50 or 100 k, but of course the
>> rest of the circuit would have to be adapted.
>> 
>> Ed
>> 
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