[time-nuts] Adjusting HP 5065A frequency

Sun Oct 21 16:43:23 UTC 2012

John
I agree with your observations. Before my time nuts time I did make the  
mistake of getting rid of my 5065A since I did have a Shera disciplined FRK 
and  had gotten hold of quite a few HP5061A's and FTS 4000's. Big mistake. 
Gave no  attention to A/V. Phase noise yes but I went about it by focusing on a 
low noise  100 MHz XO PLL as part of low noise signal generators, my key 
interest.
Recently how ever I was given a 5065A RVFR and thanks to Corby I know its  
performance and I am combining it with later technology, M1000, temperature  
control and a modified Shera, hoping for some outstanding results. If you 
are  interested contact me off list and I send you some pictures. Will take 
some time  to complete because of some other time nuts projects one of which 
I hope Corby  will report on. 
Bert Kehren

In a message dated 10/21/2012 11:58:56 A.M. Eastern Daylight Time,  
jra at febo.com writes:

Hi  Edgardo --

One slightly frustrating thing about the 5065A is that its  frequency 
settability isn't as good as its short term stability.  I  believe the manual 
says that the small divisions on the C-field counter dial  are 2x10e12, and 
it's hard to set closer than that.

A good 5065A is a  remarkable piece of gear, with medium term stability 
over, say, 1K to 100K  seconds that is very hard to beat by anything other than 
a maser.  As  best I can measure mine against a number of other sources (no 
maser here,  sigh), it is around 1e13, maybe a bit better, over that range. 
 That's an  order of magnitude better than any of the telco Rbs.

This is just a  guess, but from some data that tvb and others have 
reported, I suspect that  external tempco is the main limiter for medium term 
stability in the  5065A.  It would be interesting to see one in a 
temperature-controlled  environment vs. one that's not.

John

On Oct 21, 2012, at 11:11  AM, Edgardo Molina <xe1xus at amsat.org> wrote:

> Dear  Corby,
> 
> Good morning. Thank you for the detailed instructions  to bring the 5065A 
close to desired frequency. I couldn't have a cleaner  explanation of the 
process. 
> 
> Yesterday evening I tried  adjusting the C field in small steps using a 
mixer, lpf and two oscillators  setup as my current frequency counter is not 
able to resolve de small  increments/decrements of frequency adjustment. 
Still I could detect the  adjustments as I performed them. The response is 
quite fast. I have been told  that these units are really stable compared to the 
small telecom Rb units. I  heard a comment that the 5065A is even more 
stable than the new Symmetricom  units using the X72 Rb module. Have you ever 
measured such differences in  stability?
> 
> Thank you.
> 
> Regards,
>  
> 
> 
> 
> Edgardo Molina
> Dirección  IPTEL
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> On Oct 19, 2012, at 5:55 PM, cdelect at juno.com  wrote:
> 
>> Edgardo,
>> 
>> You do use the  C-field adjust to put a 5065A "On frequency". The Factory
>> values  are a moot point after all these years!
>> 
>> Just  incrementaly adjust the c-field control in small steps while
>>  observing the frequency comparison. 
>> 
>> The only thing  that might happen is that you reach one end of the 
C-field
>> pot  before getting to the frequency you want.
>> 
>> If that is  the case you will need to set the synthesizer switch to the
>> next  value in the chart. (either up or down depending on which way you
>>  ran out of room.)
>> 
>> Then start over with the c=field  adjustment.
>> 
>> If you switch the synthesizer setting you  will need to remove power
>> momentarily to reset the synthesizers  lock indication circuit. Otherwise
>> pushing the logic reset button  to get the green light wont work.
>> 
>> Corby
>>  ____________________________________________________________
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