[time-nuts] RFTG-u REF 0 Z3812 as cleanup module for FEI5680A
Bob Camp
kb8tq at n1k.org
Wed Nov 19 19:29:55 EST 2014
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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