Fun with a Racal 9480 with OCXO & 40 10Mhz outputs  -  (8x 5 chan) - Page 1
Forum section: electronics / testgear

author: bingo600
author_rank: Super Contributor
timestamp: March 21, 2015, 09:13:09 am
content: GuyzzI just got a Racal 9480 with OCXO & 40 10Mhz outputs - (8x 5 chan) from KJDSUpdate: The 9840 has an Opt 04B sticker on the back , so i suppose its a 04B OCXO inside it , also used in some of the 1991/2 counters.And decided to connect it to my Phillips PM6680BMy HP 5370 has a fan, and SWMBO hates fannoiseI'm using my Tbolt GPSDO as input on the PM6680B ext-ref.Racal ontime is approx 45 hr's , so the OCXO hasn't settled yet. And i haven't adjusted it yet.Just logging the stability.Playtime ....http://www.ebay.de/itm/351323826114Measuring the :Racal 9480 with OCXO & 40 10Mhz outputs - (8x 5 chan)I have fumbled around with my PM6680B (ext ref Tbolt GPDSO) , linux-gpib python bindings , and a Beiming USB-GPIB adapter (100% HP Compatible)I'm measuring on one of the 40 outputs , not the master in front (I want to see it from a clients side)Code:## Line looks like this : 1 2 3 4 5 6 7 8 9 10 11# measline Collums : Date;Time;DateTime;Temp;F-Max;F-Min;F-Mean;F-SDEV;## 1 2 3 4 5 6 7 8# 2015-03-21;08:47:39;2015-03-21T08:47:39;24.5625;+9.99999886905E+006;+9.99999886353E+006;+9.99999886717E+006;+1.51490921548E-003;#Output (.csv)2015-03-21;08:42:23;2015-03-21T08:42:23;24.5625;+9.99999887083E+006;+9.99999886348E+006;+9.99999886857E+006;+2.14294251018E-003;2015-03-21;08:42:34;2015-03-21T08:42:34;24.5000;+9.99999887071E+006;+9.99999886380E+006;+9.99999886809E+006;+2.18569307406E-003;2015-03-21;08:42:46;2015-03-21T08:42:46;24.5625;+9.99999887181E+006;+9.99999886591E+006;+9.99999886918E+006;+1.99033610964E-003;The counter is saving 10 readings , 1 sec trigger , and doing statistics on the readings.I'm just reading out the 4 statistics values , and retriggering the counter for 10 more readings.Seems like there is a 1s overhead , so each measurement is 11 sec apartBut it was a "tough" , but learning experience.Mostly to figure out the PM6680B commands.But i actually spent the most time fumbling with detecting the REQ bit on the GPIB-Bus , from inside the linux-gpib python bindings.The Racal can also take the Tbolt 10Mhz as input , and will automatically detect an ext-ref and switch from OCXO to Ext-ref.But i'm testing the OCXO now, turnon time approx 45 hours , so the OCXO is prob not stable yetI guess i'm fit with enough channels for my instruments for now.Attached some newly created .csv files from my python scriptAny suggestions (examples) for fun measurements are welcome.Edit: Added some more measurements/Bingo

author: KJDS
author_rank: Super Contributor
timestamp: March 21, 2015, 11:36:54 am
content: I think these were last adjusted about 10 years ago, so to only be 1.2Hz low is testament to how good they are.

author: Howardlong
author_rank: Super Contributor
timestamp: March 21, 2015, 12:17:26 pm
content: Thanks for the heads up, just bought one. Looks like they have an external ref input too, so can be used as a distribution unit for a rubidium or GPS disciplined source also.

author: bingo600
author_rank: Super Contributor
timestamp: March 21, 2015, 01:28:31 pm
content: HowardKJDS have manuals.But they should also be on ko4bb , thanx to a kind fellow time-nuthttp://www.ko4bb.com/manuals/index.php?dir=Racal/Bingo

author: Mr Simpleton
author_rank: Unknown
timestamp: March 21, 2015, 07:08:49 pm
content: @Howard.... so you're the oneI was trying to make up my mind if I "needed" a box like this...and poof gone. No need to make room itGuess I should thank you

author: Howardlong
author_rank: Super Contributor
timestamp: March 23, 2015, 10:27:58 pm
content: Quote from: Mr Simpleton on March 21, 2015, 07:08:49 pm"Need" and "want" are two different concepts!I already have a Rb source to which I added my own homebrew distribution amps about ten years ago. It works fine for simple frequency measurement but it suffers from serious jitter/phase noise because I built it on veroboard, not a properly laid out PCB, so it's not so good for some other applications. The only other advantage with my current setup is that I have some older bits of TE that need 2MHz and 5MHz, so I might pull my finger out and do it properly. One other plus I suppose with my current setup is that I routed all the distributed outputs to the front panel.Sorry you missed out!

author: bingo600
author_rank: Super Contributor
timestamp: April 16, 2015, 06:27:25 pm
content: My Racal OCXO seem to have settled now.Here is logging from yesterday.My PM6680B is taking 60 readings (one/sec) , calculating Fmax,Fmin,Fmean,StdDevThen logging the calculated results (one per minute)That's not bad at all for a freerunning osc./Bingo