[time-nuts] Lucent RFG-RB

[Dr Bruce Griffiths]

Rex wrote:
> I just received a Lucent RFG-RB (no -m- in this one) rubidium unit eBay
> buy from the lady in Atlanta. Thought I'd share a few notes on what it
> is. Maybe some of this has already been covered -- I lost track of all
> the emails.
>
> Like John, I immediately opened it up, haven't tried it yet, and won't
> for a while.
>
> No GPS, as has been noted in the other messages, that seems to be in the
> crystal unit. This one was made in 2000. Inside mine, the main component
> is a Datum LPRO 102500. Seems to be functionally identical to the one in
> the manual here:
> http://www.symmetricom.com/media/pdf/manuals/man-lpro.pdf
>
> Box front panel:
> 3 sma's - TP (J1), 10 MHz RF Out (J2), 15 MHz Out (J4)
> 3 db9's - +24V (P1), Alarm (J3), Interface (J5)
> 3 led's - Fault, Stby, On
>
> Seems the +24V connector only uses two pins: 1 = +24, 2 = return/gnd
> I assume those two are all that's needed to make it run.
>
> Main board is made by Efratom.
>
> I don't see any connection to the rubidium C-field pin so I don't think
> there is any adjustment through the main board, just the adjustment thru
> the case of the LPRO.
>
> With some tracing, I can't figure where the 10 MHz output (sma) comes
> from. I assume it is functional, but haven't applied power yet. 
>
> The 15 MHz generation looks very similar to the other boad I described
> in another message on an FRS-C unit. The active source again seems to
> come from an Altera PLD. Maybe it divides 10 MHz by two, and (guess)
> narrows the pulse for better 3rd harmonic? 
Rex

Narrowing the pulse width does little for the amplitude of the third 
harmonic component.
There's already plenty with a 50% duty cycle square wave.
A waveform with duty duty cycle of 1/6 has the same 3rd hamonic 
component amplitude as a 50% duty cycle waveform.
Narrowing the pulse to a very small duty cycle tends to flatten the the 
frequency comb whilst reducing the amplitude of all components.
see:
http://www.wenzel.com/pdffiles/choose.pdf

Bruce
> Anyway, then it seems to go
> through a series resonant LC, with a trimmer on the C. Then thru the 15
> MHz filter, two stages of amplification, and a MCL low-pass filter to
> the sma.
>
> BITE signal from the LPRO goes somewhere so I assume it is at least part
> of the alarm connector output.
>
> If anyone finds or works out the pins on the alarm and interface
> connectors, I'd eb interested to hear about it.
>
> So there we are for now. Quick first look without even trying it yet.
> Assuming it works, the LPRO was probably worth my $130 investment. Hope
> some of my comments helps someone.
>
> -Rex
>
>
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>
>