[time-nuts] Best Rubidium Frequency Standard

Bob Camp kb8tq at n1k.org
Sun Mar 13 10:31:54 EDT 2016


Hi

Ok, so I can spend $2,500 on a working 5065A if I can find one. I can spend the same money on five working FRK’s at $500 (if I can find them). I can spend the same money on 10 working PRS-10’s (if they show up). I can spend that money on 40 working with a warranty telecom Rb’s right at $125 each now any day of the week. I can get 200 of the “repair” grade telecom Rb’s for the same money. 

Yes that neglects shipping and it also does not include your time spending a year or two shopping for this or that. 

Let’s say that the buyer is 65 years old. Let’s also guess that by age 95 this stuff isn’t going to be of much interest. 

Based on their history, the 5065A will need a pretty major rebuild over the course of 30 years. 

The FRK’s each would need to run for 6 years to keep you going for the time period. That’s a reasonable bet, but not a slam dunk based on my data here.

The PRS-10’s would need to work for about 3 years to last you that amount of time. None of mine have run that long and I do not seem to be the only one who has seen that. 

The telecom Rb’s would need to run for less than a year to make it. That’s a slam dunk. In fact it’s a slam dunk with 15 of them. 

The repair units are a bit of an unknown. If you get 120 working units, they need to each last 3 months. That is indeed a slam dunk. If they each run for 2 years (the unknown) you are back to 15 units. 

Can I call up and get a PRS-10 repaired today for the same cost as a replacement unit on eBay? Maybe I can. If so how long does it run after the repair compared to the eBay part. If it’s no better than the eBay unit, the math does not change. If in 10 years they stop doing that, the math changes a bit. 

Can I call up somebody and get a 5065A rebuilt? I suspect that there is *some* amount of cash I can throw at him to do so. Expecting him to do if for free … that’s crazy. Is somebody still rebuilding the 5065’s in 15 years … who knows. I’d bet it does not get cheaper.

Can I call somebody and get any of the other stuff repaired? I suppose I can if I was offering $5,000 for the repair. (No I’m not offering so no need to email me). Once you get past the simple stuff, it’s not easy to fix this stuff. 

===

So based on a “bang for the buck” estimate:

The rebuild units come out on top

The working telecom units come in second

The FRK’s come in third

The others come in someplace further back than that.

===

Even simple repairs on theses are far more complex that manually setting an Rb on frequency against GPS. The more involved repairs are way more complex that a manual frequency set. To me that makes a “auto locking” unit that likely needs complex troubleshooting a much less attractive thing. Yes, that goes into the numbers above. 


Bob



> On Mar 13, 2016, at 1:18 AM, Mark Sims <holrum at hotmail.com> wrote:
> 
> In many ways the 5065A is the probably the most repairable of all the units (closely followed by the FRK family and the M100).   They all use parts that are mostly still available and the circuitry is accessible.  You can assume that the lamp (and maybe some of the microwave parts) in any Rb oscillator is unobtainium.  
> Most failures seen in these systems tend to be in the power related parts (electrolytic caps and heater / lamp driver transistors).  Total rubidium lamp failures are rare.  Lamps with degraded output due to rubidium depositing on the lamp walls can usually be refurbished with a heat gun.
> If you don't need the ultimate in performance the telecom Rb's are a very good value.   They can be had for prices where repair is not an issue... just replace them.  At one time LPROs could be had for less than $50 and they were usually in good operating condition.   The bulk packs of the TEMIC units on Ebay approach that level today.  As time has passed the availability has gone down,  prices have gone up,  and the quality what is available had gone down. 		 	   		  
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