Racal-Dana 9475 Rubidium Frequency Standard - Page 1
Forum section: electronics / testgear

author: balu
author_rank: Regular Contributor
timestamp: February 04, 2018, 02:03:43 pm
content: Hello,I got a new test gear. This is a Racal Dana 9475 Rubidium Frequency Standard from 1983 (I think). This unit has a weight of approx. 5.2 kg (11.5 lb.) and a dimensions of 132 x 232 x 270 mm (5.2 x 9.1 x 10.6 inches). On the front panel is the main power switch, a power LED, three LEDs for the signal output, an oscillator lock-in indicator LED, a voltage gauge and a voltage display section switch. The Racal 9475 has three isolated and protected 1 MHz signal (> 1Vrms @ 50 Ohm) outputs and one 10 MHz (> 1Vrms @ 50 Ohm) output. The Racal 9475 used an EFRATOM (Model FRK) rubidium frequency standard.

author: balu
author_rank: Regular Contributor
timestamp: February 04, 2018, 02:05:56 pm
content: Hello,I some mor photos

author: balu
author_rank: Regular Contributor
timestamp: February 04, 2018, 02:07:31 pm
content: And more photos

author: Vgkid
author_rank: Super Contributor
timestamp: February 04, 2018, 03:28:23 pm
content: Pretty cool , I like the warning on top of the rb oscillator.

author: edpalmer42
author_rank: Super Contributor
timestamp: February 04, 2018, 04:01:29 pm
content: The FRK is one of my favorite Rb standards. Full schematics, pure analog - no processor, and big enough that if repairs are required, you can actually see the parts!Ed

author: balu
author_rank: Regular Contributor
timestamp: February 05, 2018, 02:34:29 pm
content: Hello,After a short repair (just a broken wire between transformer and rectifier) I can power on the Racal 9475. For about 10 minutes the oscillator control voltage changes between 12 and 6 V and the lamp voltage was approx. 6V (see photos). The 10MHz and 1MHz output looks stable. I use a 50 Ohm terminator with a T and x1 Input of the oscilloscope for the measurements until the rubidium frequency standard is in lock mode.

author: balu
author_rank: Regular Contributor
timestamp: February 05, 2018, 02:40:07 pm
content: Hello,After warm up (approx. 10 minutes) the rubidium frequency standard goes into lock mode. I used a 20dB attenuator for the spectrum analyzer measurements and a 50 Ohm terminator with a T and x1 input for the oscilloscope measurements.

author: edpalmer42
author_rank: Super Contributor
timestamp: February 05, 2018, 04:57:33 pm
content: I'm sure that the frequency is closer than 10.0307 MHz, but you'd need something like a GPSDO to compare it to.Ed

author: ChrisLX200
author_rank: Unknown
timestamp: February 05, 2018, 06:17:55 pm
content: I was looking for one of these myself for a few months but the asking prices were always high - around £800. In the end I bought a Racal 2202 counter (which has an internal Rb standard) for a fraction of the price and it now provides my external ref. The problem with these 30yr-old devices is that the physics package is going to be reaching its end of life so unless it has already been replaced then durability is of concern. I'm not sure whether it's better to leave the thing powered up 24/7 or only turn it on when needed, the fan is quite noisy for one thing but obviously it takes time to stabilise. My 2202 achieves lock within 5 minutes (which is good), there is no indicator but it's connected to another counter so I can observe it sweeping up/down prior to locking.

author: edpalmer42
author_rank: Super Contributor
timestamp: February 05, 2018, 06:53:05 pm
content: I don't know anything about the 2202r. If you can monitor the lamp voltage, see where it is in its 'acceptable' range and monitor it over time. I've got an FRK that's been running for maybe 5 years and the lamp voltage hasn't moved. As long as that's stable, the physics package is probably okay. Other than that, you're looking at electrical failures that are similar to any other piece of complex electronic equipment.Ed