Max is correct. The GR 1120-AB contains the following units in a standard relay rack:
The GR Standard Frequency Oscillator 1113-A with an output frequency of 5 MHz. This unit is settable to 1 x10 -10 with an output of 1 V RMS. Located in the relay rack above the Standard Frequency Oscillator is the GR Frequency Divider 1114-A (all discrete transistor) with inputs of 5 MHz, 1 MHz and 100 MHz and outputs of 1 MHz (Sine), 100 kHz (Sine + Square), 10kHz (Sine + Square), 1 kHz (Sine) with two output jacks and 100 Hz (Sine) with two output jacks. There were plug-in options that provided additional outputs of 400 Hz and 60 Hz output but unfortunately I don't have either option installed. Installed in the relay rack above the Frequency Divider is the GR Syncronometer Time Comparitor 1103-B. The GR 1103-B uses a 1 kHz motor and 24 hour clock to display the integral of the number of cycles executed by the standard frequency oscillator as a standard time interval. The GR 1103-B contains a set of dry contacts that open one each second for 0.05 seconds. In the mid-1960s, this time standard was compared to a standard time radio station, such as WWV, using the GR 1103-B. While this a beautiful piece of mechanical gear, a HP 117A is much easier to use. The bottom of the relay rack includes the Battery Storage drawer, the GR 1268-A Automatic Battery Charging Unit and the GR 1116-B Emergency Power Supply. These three pieces of equipment are capable of maintaining power to the rack for four hours in the case of commercial power failure. This particular GR 1120-AB, rack number 195, was donated by General Radio to the Moore School of Electrical Engineering - University of Pennsylvania in 1965. The equipment was assigned to the School's Valley Forge Research Center in the late 1960s and remained there serving as the time standard for a number of research projects. By the late 1970s, the GR 1120-AB was stored in an unheated area at Valley Forge and was unused. I was granted approval to remove the Standard after approaching the administration at Penn. Otherwise, it would probably be in a landfill today. My work to completely electrically and mechanically restore this Standard started in May 2004. Once the inner oven thermoswitch is replaced and tested, the Standard will be completely operational. Probably one of the few remaining GR 1120-AB racks in the world. -----Original Message----- From: Max Robinson <[EMAIL PROTECTED]> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Sent: Sat, 23 Aug 2008 1:19 am Subject: Re: [time-nuts] Restoring GR 1120-AB Frequency Standard There must have been several different versions of this unit. The oscillator I have is 5 MHz. The frequency dividers in the rack I got it out of were discrete transistor construction. Seems to me the clock used a 25L6 although I don't remember how they derived the heater voltage. There was also a phase locked frequency multiplier with outputs at 10 MHz, 100 MHz and 1 GHz. The frequency divider module had outputs down to 1 PPS. After typing that I'm not sure the oscillator frequency is right. Maybe it's 1 MHz. I'm sure it's not 100 kHz. Regards. Max. K 4 O D S. Email: [EMAIL PROTECTED] Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with tubes group send an email to, [EMAIL PROTECTED] ----- Original Message ----- From: "phil" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Friday, August 22, 2008 10:15 PM Subject: Re: [time-nuts] Restoring GR 1120-AB Frequency Standard > > ----- 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. > > _______________________________________________ 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. _______________________________________________ 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.
