Racal Dana 9914  - Page 1
Forum section: electronics / testgear

author: Flump
author_rank: Frequent Contributor
timestamp: June 19, 2014, 10:43:06 am
content: Has anyone had any experience of this frequency countergood or bad ?I just bought one as my current optoelectonics handy counter 2810can drift up to 10 Hz from day to day and I am hoping the 9914will be better.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 19, 2014, 01:34:33 pm
content: The stability will depend on which oscillator it has in it. Best is 04E, then 04B which are ovened. I'm sure the 99xx series had an option for a plain xtal oscillator - 04C I think - which you would want to avoid unless you intended to run it with an external standard.Note the external standard input on these was 1MHz, not 10MHz which is usual on more modern equipment.These rely on an unobtanium counter chip custom built by Ferranti so make sure you see it working.

author: Flump
author_rank: Frequent Contributor
timestamp: June 19, 2014, 08:47:06 pm
content: thanks very much for the info docI bought it because A it was cheap and B it had to be better than my current counter.Okay so it looks like it has a standard Xtal oscillator,would the 1Mhz check reading on the display be a good indication if the crystal is is ok and accurate ?or are there other tests I can do to determine if it needs to be upgraded ?.I found this on ebay, would this be a good upgrade for it ?http://www.ebay.co.uk/itm/PRECISION-1PPM-1-000MHz-TCXO-/380174345926?pt=LH_DefaultDomain_0&hash=item58842826c6I am not sure about the external standard input, I will do some googling on thatAny more info / advice anyone can share I would appreciate it.Here are a few pictures of it.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 19, 2014, 09:04:12 pm
content: Quote from: Flump on June 19, 2014, 08:47:06 pmUnlikely. The 1 MHz check is almost certainly a check of functionality of the counting circuits. It tells you that the crystal oscillator is functioning but not what frequency it is running at (it is checking itself against itself). If you have an oscillator and a longwave radio you could beat that oscillator against BBC radio 4 on 198kHz. you should be able to get within 1Hz with relative ease, this will give you a rough check of the accuracy.I have two Racals, their long term stability is excellent, but, the OCXO can take up to 40 minutes to warm up from cold before it is on-song.

author: Vgkid
author_rank: Super Contributor
timestamp: June 19, 2014, 09:05:33 pm
content: You could grab a 10 Mhz ocxo and throw it through a ls90 to get your 1Mhz.

author: Flump
author_rank: Frequent Contributor
timestamp: June 19, 2014, 11:28:30 pm
content: I would love to vgkid, if i knew how

author: Andy Watson
author_rank: Super Contributor
timestamp: June 19, 2014, 11:40:05 pm
content: Quote from: Flump on June 19, 2014, 11:28:30 pmSubstitute 74ls90 for ls 90 and see if that gets you anywhere

author: Flump
author_rank: Frequent Contributor
timestamp: June 20, 2014, 01:23:29 am
content: Thanks AndyI found the datasheet for it but there are no examples of how to wire it up,I looked on google too and cant find one.I feel like such a noob sometimesAtleast those chips are quite cheap at £2.93 on uk ebay

author: Vgkid
author_rank: Super Contributor
timestamp: June 20, 2014, 02:38:00 am
content: It is from the Fluke 1952 counter manual, only 1 LS90 is needed.Look at the bottom of the page, U3/U4/U5actually, here is a better examplehttp://circuit-diagram.hqew.net/Frequency-Divider-For-Measurements-Circuit_17100.html

author: Flump
author_rank: Frequent Contributor
timestamp: June 21, 2014, 04:07:40 pm
content: thanks for the diagrams vg kidI have ordered 1 of these and it should be here soonhttp://www.ebay.co.uk/itm/390699562045?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649To be honest I still dont understand how to get the 10mhz to 1mhz using 1 chip as i dont understandthe datasheet fully, but I am looking forward to playing around with it to see if I can work it out

author: babysitter
author_rank: Frequent Contributor
timestamp: June 23, 2014, 08:22:29 am
content: Hi Flump,these are logic ICs which contain some dividers. First page of your PDF explains what you need to do:QuoteTo-do: Turn your 10 MHz sine from OCXO into a logic level signal (TLL, as rectangularish as possible, anything which goes belov 0.8V and above 2V is sufficient. This signal should go into input B of the 74LS90, on QA comes the 1 MHz Signal, also a 5V logic signal but with 1 MHz.Clip, attenuate, higpass filter the output until it fits the requirements of your counters reference input.Alternative pathway, you might consider buying a QH40A xtal heater from Kuhne electronics (DB6NT, around 12€) to temperature-stabilize your internal references xtal, and check if it is already more stable. If the internal reference has a trimmer for adjustment you might consider reducing the trimming range.

author: Flump
author_rank: Frequent Contributor
timestamp: June 23, 2014, 11:33:31 am
content: Hendrik to the rescue again!How on earth did i miss that in the PDFI am really looking forward to having a play with that chip now,still waiting for the mail to arrive but i'm hoping it might come today.Never heard of those crystal heaters before, they are a great productand added to my bookmarks incase i need them in the future.I don't really want to change anything inside the counter so I thinkI will use an external reference first and see how that goes.