----- Original Message ----- From: "Magnus Danielson" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Friday, August 22, 2008 5:25 PM Subject: Re: [time-nuts] Restoring GR 1120-AB Frequency Standard
> phil wrote: >> Gentlemen, >> Original poster is trying to "RESTORE" this entire old General Radio >> Standard ( a rack of equipment) to it's "original" glory. >> He simply needs a part, a unique thermoswitch or a way to fix it, not >> retrofit an atomic engine! This is a museum class instrument, 100kc. >> >> May I suggest start a new thread on the better/best merits/design of >> temperature control. >> Makes it rather difficult to follow a thread as the subject has changed. > > My proposal to use capacitive sensing rather than conductive sensing > would handle the electrode oxide issue. It is meant as a means to go > around the sensing issue with parts at hand and only some new electronic > design of very simple form, not the means to supercalibrate something. > > I guess this only shows that time-nuts are time-nuts... > > Cheers, > Magnus Magnus, Perhaps this will help understand why I made that comment. That old "primary" standard was quite a contraption. This things heyday was in the order of 1950's and used up into the 60's and some models into early 70's. Of course it was all tube equipment. My unit model was possibly a 620, it predated what Russ has (1100) but was quite similar in design. Russ's unit has all the multivibrators in one housing where mine was each separate. I think his is a 100kc oscillator and mine was 50kc. As I remember the one I had was in two 7-foot racks, a standard side and frequency measuring side. My oscillator was 50KC though about 300 dollars in the mid 6o's would have bought a 100kc quartz bar to upgrade it The unit had each module or circuit in a separate 19" rack space all averaging 8 inch high The main components, a power supply, oscillator (about 20 plus rack inches high by itself), separate multivibrators of 100kc, 10kc, 1kc, and 100 cycles. Yes they were called multivibrators though all tube. It also had a syncronometer at the top of the rack, better known as a clock. Apparently the crystal was rich in harmonics and they made use of it in this assembly. That clock ran off of the 1 kc output. The heart of the oscillator, main part of this contraption used a quartz bar about 3/8 of an inch square and about 2 inches long suspended on 4 springs. If I recall it was a single oven but it's specs called for about .01-degree regulation. I don't remember all the fine details, but it had many other components (all seperate rack units), a separate 5kc interpolation oscillator, amplifier, and even an 8-inch speaker to zero beat the standard to another unit, talking about phase lock! So as you can see, these vintage units only use/value is that of an antique or conversation piece. A 10811 would blow it away performance wise. Now with an understanding of that old antique, that discussion was like putting an electronic ignition in place of the old Ford Model T spark coil. You could, but .. You just search for the part. So it's not a "time-nut" issue as such other than appreciating the history or the evolution of time. I can see from the varied posts this is one heck of a super talented group. I guess we all get involved in something interesting and easily get carried away, as in the discussion. Granted you can do a given task many ways, and bantering ideas around is how things are born and perfected. Only problem is, it doesn't locate an "original" antique part, what he stated he wanted! That old GR stuff does occasionally show up, most free to haul off it's so massive. A bunch of the old vintage GR standard parts was listed as a lot on ebay some months ago. Someone asked what happened to my old GR stuff. I disposed of over 100 tons of old electronics that had accumulated including this old GR stuff. One of my sidelines was the used equipment business and the sales of tube stuff died. I had some 15,000 feet of "junk" as I call all this stuff. By the way, according to Bruce, that design of the old "thermoswitch" achieved resolutions as fine as .001 degrees. It would be hard to build any electronic sensor of any design that is that reliable and repeatable (.001 degree) with a "one-time" factory calibration good for a life exceeding 50 years without using a similar sensor design. The unit in question with the electrode in mercury design lasted about 50 years before showing it's age and misbehaving. Phil _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.