[time-nuts] Some more info on the 5065A optical unit

Bob kb8tq kb8tq at n1k.org
Mon Nov 27 12:47:03 EST 2017


If the coil form really is plain old cardboard. I wonder what the impact
of humidity is? With the heat rise and all the packing, it’s going to be 
a pretty indirect effect. It might be an issue on a unit that had been stored 
powered off for a number of years. Straight cardboard *is* an issue on
RF coils in humidity.


> On Nov 27, 2017, at 12:34 PM, cdelect at juno.com wrote:
> Made some measurements on a 5065A optical unit.
> -There are 3 layers in the magnetic shield.
> -There is about 1/8" of insulation between the
> outer and middle, and between the middle and inner shields.
> -The C-field winding is wound on a cardboard form that 
> fits tightly into the inner shield.
> -There is almost 1/2" of foamed insulation between the C-field
> winding and the cell and oven forms and windings.
> Per Poul-Hennings data a 3.25 deg C change of the outer shield
> will result in a 1 deg C change in the C-field coil. 
> This equates to a 3.4X10-14 frequency shift when not using 
> active current drive.
> If the outer shield is actively held to plus/minus 1 deg C then 
> the shift will be held within plus/minus 1.05X10-14 as long as
> the ambient temperature stays within the regulating range of the 
> PC liquid cooler.
> Cheers,
> Corby
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