[NLRS] FWD: re: low cost, rubidium oscilators available

[tosca005 at umn.edu]

On Nov 9 2008, Jim Froemke wrote:

>The San Bernardino Microwave Society members Have been able to get 
>LPRO rubidium oscillators used for about $67 and been selling them to 
>members mostly.

Seems like nowadays I run into too many people who are too busy to RTFM so 
I will summarize a few good and bad points gleaned from my examination of 
the PDF files that Jim kindly linked to the original posting, and a little 
Googling around the Internet for more information. (Of course one of my 
email postings is typically long enough to induce readers to skip over the 
details too, so maybe this is not going to help much! :(

The good:
  1) Fairly compact, approximately 4" x 5" x 1.5" package
  2) Easy connection: minimum is 2 pins for power and 2 pins for 10 MHz out
       Almost Plug 'n Play!
  3) Optionally, a simple circuit can monitor for Rubidium osc lock
  4) Full specified performance between -30C and +70C (-22F to 158F), so
       temperature should not be a problem unless you tolerate much worse
       extremes than I do :)  Even if you decided to rove in January with
       one of these feeding your transverter(s), just keep the standard in
       the car and temperature shouldn't be a problem.
  5) Long-life lamp, designed for 10 year life
  6) Fairly fast turn-on to accurate output time:
       -- 3-4 minutes to atomic lock, accuracy +/- 5e-8
       -- 30 minutes to "full accuracy" (not defined in spec sheet!)
  7) At 5e-8 accuracy, your 10368.1 signal should be +/- 520 Hz! If the
       unit is even more accurate after full warm-up, you'd be even closer!
       The spec sheet implies better accuracy after full warm-up but I did
       not find what the full accuracy spec really is...

       URL http://www.leapsecond.com/museum/lpro/ may have the info, but I
       am reluctant to try to interpret the plots myself. Any takers?

       From URL http://www.gpstime.com.cn/downloads/Lpro.pdf if this is the
       same model, it looks like you can expect +/- 1E-9 or better after 
full
       warm-up, or +/- 10.4 Hz at 10369100000 Hz (10.3681 GHz). Wow!

       From URL http://www.technical-sys.com/QL%20LPRO%20DS.pdf it seems
       like worst-case including aging for 1 year is +/- 5e-10, or 5.2 Hz
       on 10368.1 MHz after full warm-up, if this is the same model.

The not so good:
  1) Needs 24 VDC at 1.7 amps (peak) at turn-on, typically 0.5 amps 
sustained
       which is not a problem for a home station, but another annoyance for
       most rover stations, especially because you'd want to run it for many
       hours at a time in most contest situations. Or maybe not, with less 
than
       5 minutes to 0.5 KHz accuracy on 10 G, if you turned it on and off at
       each rover stop.
  2) Heatsink recommended, even for room temperature usage, so plan on 
needing
       a little more room than the quoted package size.
  3) How "used" are they? If they have been operated already for 10 years,
       there may not be much life left in them.
  4) As Donn already posted, they seem to be selling faster than the seller
       can get them, but no information on how long the waiting list delay 
is
       at this time (I'm sure Donn will tell us if/when he gets his).

I picked up one of DEMI's N5AC synthesized oscillator board upgrade kits 
(A32RFK) at MUD, and also won a coupon to have DEMI upgrade a DEMI 
transverter for me, to use an A32 board in place of the MicroLO board, so 
this subject is of a lot of interest to me. But I also have a 
GPS-disciplined OCXO reference oscillator that needs to be assembled and 
tested, so I'd like to see how well that performs before investing in more 
parts such as these Rubidium standards. But of course, the siren call of 
"(nearly) no assembly required" is always tempting!

Thanks for forwarding the information to the NLRS reflector, Jim! I hope 
some of the locals manage to snare one or more of these standards and can 
tell us how the integration into their systems went.

73 de W0JT