[time-nuts] FRK specs.....

EWKehren at aol.com EWKehren at aol.com
Sun Aug 12 12:13:14 EDT 2012


In the commercial world a PRS10  is most likely the best but for  time nuts 
even at the surplus price in my opinion it is all hype and a waste of  
money. Have you looked closely at the specification and the design. Frequency  
accuracy can not be better than 1 E-12 since the OCXO is driven strictly by a 
 DAC and the A/V is for time nuts nothing to write home about. Any digital 
loop  controlling a Rb  in tern with an analog loop controlling a selected 
HP  10811 or for that matter a Morion will outperform a PRS 10.
I have a FRK-H controlling a HP 10811 that has an A/V below 1 E-12 from 1  
to 100 seconds, I modified the FRK loop and the 10811. On the 10811 it is 
easy  to get to the bottom PCB and without un soldering any component or 
further  disassembly cutting two traces and two jumpers you end up with a 2 to 12 
Volt  tuning voltage, perfect for a FRK or M100.. A second option is to use 
a separate  analog loop with a time constant suitable for your OCXO.
By the way the FRK-H is not lower noise but factor 2 lower aging with the  
proper OCXO not an issue, since hopefully you discipline it with GPS.
For 12 years I have used Shera in that application recently switching the  
DAC to a  LTC1655. Has served me well over the years.
Other Rb's will do also a very credible job. On one extreme a FEI 5680 is  
waiting to be integrated with a MV180 on the other extreme a HP5065 RVFR  
assembly will be integrated with a M1000 OCXO along with state of the art  
circuitry.  
Bert Kehren
 
 
 
In a message dated 8/12/2012 8:09:54 A.M. Eastern Daylight Time,  
wa1zms at att.net writes:

Thanks  Tom.  

I agree, the SRS seems to be the best
overall Rb except  maybe on old HP if one is willing to spend about the 
same price on a 20 year  old unit.  The SRS units I bought for work were only 
$2700 with chassis,  rack ears and multiple outputs.



-Brian, WA1ZMS

On Aug  12, 2012, at 3:17 AM, Tom Knox <actast at hotmail.com> wrote:

>  
> Hi Brian;
> There are a few decent rubidium oscillators short  term like the SRS but 
none are great, in my humble opinion you are much better  off disciplining a 
good quartz oscillator off your LPRO.
> Best  Wishes;
> Thomas Knox
> 
> 
> 
>> From:  wa1zms at att.net
>> Date: Sat, 11 Aug 2012 21:56:13 -0700
>>  To: time-nuts at febo.com
>> Subject: [time-nuts] FRK  specs.....
>> 
>> I used to be of the opinion that the  Efratom FRK-H was the best of the 
models of FRK Rb standards for both  short-term stability and overall 
performance.
>> 
>> Is that  still true today?
>> 
>> I know there are better solutions  for short-term (BVA OCXO) and long 
term
>> (Cs & MASERS). But  where to things stack up today?
>> 
>> I'm looking to buy an  Rb that's better than my LPROs and other models.
>> But I do not own  an FRK-H.
>> 
>> Looking for comments, please.
>>  
>> Thanks in advance,
>> -Brian, WA1ZMS
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