alex mclaggan wrote:
Like many of you, I have seen these advertised on Ebay at good prices. Also, like many of you, I am confused about the 'programmability' and connections. Many of them advertise these connections:-PIN 1: INPUT +15V to +18V PIN 2: GROUND PIN 3: LOCK/UNLOCK (high = unlock) PIN 4: INPUT +5V PIN 5: GROUND PIN 7: OUTPUT ( 10MHz sinewave ) Many of them also say "Digitally programmable to 1x10-13", with the above connections. (Many of the sites seem to have the same descriptive text.) On questioning one of them about how the programming was done, they replied "Not with this model; only with the more expensive one he sells !" But from what I read in some of the time-nuts contributions, there is sometimes (?) or often (?) also these connections:- Pin 6 1 pps out Pin 8 RS-232 Rx (into rubidium) Pin 9 RS-232 Tx (from rubidium) Can anyone tell me if they ALL have the MAX level shifter/driver chip fitted, even though it may not be connected to the connector ? I don't want full programmability, just 10 MHz frequency correction. Perhaps I just have to take pot luck when I buy ? What are my chances of getting one with the 'hidden' RS232 and 1PPS output ?
For what it is worth, this unit: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270870764984appears identical to the one I purchased four weeks ago. Same seller, same cut off PCB, same "extras" thrown in, same price.
My unit has the pins and functions you list above (including the 1PPS and the rs-232 connections.
I have been able to adjust the frequency in a restricted range around the nominal 10MHz. The results from my experiments can be seen here:
http://c-c-i.com/image/tid/4 Bob S.
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