>From slowly working my way thru several new to me datum 1000's I'm coming to >the conclusion that powering them up checking for output and basic >functionality (ie can the frequency be adjusted ?) followed by leaving them >alone and powered up for several weeks to a month or so is probably the best >plan if you are looking for time nuts level performance.
I believe the datum 1000 and fts 1200 are some what related. Regards Mark Spencer ------------------------------ On Fri, 10 Aug, 2012 1:31 PM EDT [email protected] wrote: >Ed >I did not see any current, but that is also due to the fact that there is >most likely at least 10 K between pin 2 and the varactor. Most likely if it >was biased for instance + 12 Volt, there would also be a resistor before >the diode. I suspect John is right that with my + voltage the diode was >forward biased and blocked oscillation. Maybe this one was strictly - tuning > >voltage, hope so. I will run it for a time and observe stability. May be >similar to HP 10811 bias. >Thanks Bert > > > >In a message dated 8/10/2012 11:28:46 A.M. Eastern Daylight Time, >[email protected] writes: > >Hi Bert, > >I see on the data sheet that the tuning voltage is supposed to be -10 to >+10 volts and that the supply voltage is +22 to +30 volts. I suspect >that one side of the varactor is supposed to be biased at one half of >the supply voltage. But in your case, it looks like that bias is now at >zero volts due to an internal short - either a short between traces or, >more likely, a capacitor failure. When you apply a positive voltage, >you're changing the DC voltages in the oscillator circuit which disrupts >the oscillator. > >When you apply a positive voltage to the EFC lead, is there a current >flow into the lead? Since a varactor is always supposed to be >reverse-biased there shouldn't be any current. > >Ed > >On 8/10/2012 4:46 AM, [email protected] wrote: >> Bjoern >> Thank you for the link I am able to change the frequency 4 Hz from - 2Hz >( >> 0V) to + 2 Hz (-12.2V) using pin 2. Reading the info that you got me >> probably explains the slot next to the connector, but I experience a >much wider >> tuning range on pin 2 and John is right any positive voltage forward >biases >> the diode cutting off oscillation. Will do some testing. >> Thanks again Bert >> >> >> In a message dated 8/10/2012 6:28:17 A.M. Eastern Daylight Time, >> [email protected] writes: >> >> Bert, >> >> Good that you got the EFC working! But I would be a bit suspicious of >> needing -13V. >> >> It seems from: >> >http://www.ece.gatech.edu/academic/courses/ece4007/08fall/ece4007l01/al4/dat >> asheets/symmetricon_oscillator_instructionsheet.pdf >> >> that the default EFC configuration is (0 to +10)V with a range of 4e-7 >> (2Hz). From the same document there are a lot of other EFC >configurations, >> but none that goes outside of +-10V. >> >> My 1200 has about 3.5Hz tuning range on (0,10)V. Se attached jpg. I did >> not check behavior on negative EFC voltage. >> >> -- >> >> Björn >> >> John, >> that did the trick I can tune it with a negative voltage, minus 13 >gives me plus 2 Hz but this unit came out of a FTS 5000 and it had a >positive >> tuning voltage. >> Bert >> >> >> In a message dated 8/9/2012 9:13:29 P.M. Eastern Daylight Time, >> [email protected] writes: >> >>> John >>> Oven did reduce in current and I can not imagine that it would be >that >>> close with an overheated oven. At 0 V it is within .5 Hz of what >they normally are. Ground has no effect but even 0.8 V on pin 2 stops >oscillation >> That's a suspicious-sounding voltage. Are you sure you're not >> forward-biasing the varicap? Maybe some of these OCXOs were >specified >> for use with negative EFC voltage. >> >> If so, then driving the diode with a negative voltage should raise >the >> operating frequency (which is what you want.) >> >> -- john, KE5FX >> www.miles.io >> > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
