[time-nuts] RFTG-u REF 0 Z3812 as cleanup module for FEI5680A

[Bob Camp]

HI

For anything short of microwave multiplication, the 15 MHz output of the Z3810/11/12 is likely to be “good enough”. The 60 KHz noise hump that may be from the power brick isn’t going to make it through a PLL going to VHF, so the only benefit of pulling the brick would be some sort of SDR running directly off of 15 MHz. A crystal bandpass filter at 15 MHz could be made (or found) in that case. The brick probably does a better job rejecting  the 50/60 Hz stuff you would get into with a direct supply setup. 

So let’s see … Nyquist at 7.5 MHz. 1/2 band at 3.75 MHz. You could have a real good radio from maybe 4 MHz on down to DC. That might be interesting, but it’s probably not going to get a lot more people buying these up to do it. 

Bob

> On Nov 18, 2014, at 9:22 AM, Bert Kehren via time-nuts <time-nuts at febo.com> wrote:
> 
> I would not mess with the power management of the unit, HP did know what  
> they where doing. Any clean up I would move off the unit if you want to stay  
> with the same OCXO you have one in the second unit. 
> As to phase noise before time nuts issues took up all my time low noise  
> signal generators where my main focus and will be again. I know of no high  
> quality Sig. Gen  that does not include a 100 MHz XO and in some cases  higher 
> frequency SAW units. And that has been going on for as long as I can  
> remember and I am 72.
> One subject no one has touched on is thermal control. I do not know but  
> suspect forced air cooling that would explain why all connectors on the front. 
> From comments by some members we are looking at 20 W. I will include a fan 
> along  with temperature control.
> Bert Kehren
> 
> 
> In a message dated 11/18/2014 12:21:32 A.M. Eastern Standard Time,  
> don_hendi at gmx.de writes:
> 
> Hello  List,
> 
> having not looked at the spectra yet as I am confined to mobile  phone 
> instead of PC often, I had the idea to marry those two well-known  
> devices to get a nice clean reference oscillator. I remember the  
> spectrum of the FEI as not so nice, and the MTI sounds  better.
> 
> 
> My understanding is yet that I would need to emulate the  REF1 unit, 
> basically need to look up the "lonely REF" tweak with the  bridges in J5, 
> maybe fake valid GPS datagrams with a microcontroller and  turn the 1PPS 
> pulse from the FEI into that 2 PPSes  expected.
> 
> Replacing the Lucent Power Brick with a linear supply and  bridging the 
> tripler to get 5 MHz out might be tweaks to increase the  output spectrum 
> further. This was discussed before, I think, i have to  look it up too.
> 
> (I wonder if the REF0 acts up after complete removal of  the source REF1 
> or keep on doing holdover which would be a nice way to  take a good 
> frequency standard to a ham radio repeater  side)
> 
> BR
> 
> Hendrik
> 
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