Having used FRK for over 35 years I am partial to FRK/M100. More later. We have had some bad experience with PRS-10 failing lamp module and others have shared the same observation. Clear sign of oxidation and we know the unit has never been exposed to water! Back to FRK. Previously mentioned bigger is better also heatsink on all Rb's are a must Fan control is better. The biggest drawback of FRK and M100 is availability of lamps. At one time you could buy them for $ 300. I have spares for our team. If you buy one make sure lamp voltage is at least 8 Volt. Many of the M 100's have not seen continuous duty. The question is what do you want. We are frequency nuts and use FRK and M100 with active Fan control and keep the backplate to 0.01 C. Typical aging is below 5 E-14 per day over a 600 day period. An other plus is to the best of my knowledge M 100 have the only measured pressure sensitivity test data. Data would also apply to FRK's. Quite a few time-nuts have controlled these Rb's with a Shera contoller I included. The weakness of Shera is the AD1861 audio DAC. At one time we did a detailed analysis of available DAC's, went as far as designing and building a test board capable of auto testing multiple DAC's using the LTC2400 and decided for Rb's the best DAC is the 16 bit LTC1655. If not M100/FRK with what is out there I would go with Skip's RDR Fe5650. (no commercial interest) We have a couple of them. From what I can tell there is a high degree of similarity with the 5680A different packaging. There is a lot of data available, there was at one time a FE5680A frenzy after I did my first post based on some recommendation from Germany where they enjoyed popularity at least a year before us. What happened to our German time nuts? What comes now out of China I would not touch, my second order was so bad I had to return it. I doubt that Skip's units ever saw China, he may want to comment on it. As I mentioned in my first post and confirmed subsequently there are frequency spikes on the output and a cleanup is mandatory, I have a plot it was done with a HP5065A and time pod, maybe byTom? Cooling is low cost with a Laptop heatpipe/fan. Frequency control can be done with RS232 or a GPSDO. Cash Olsen is ready to ship first set of units for $65 plus shipping. Bert Kehren In a message dated 3/12/2016 11:02:12 A.M. Eastern Standard Time, kb...@n1k.org writes:
Hi The PRS-10 generally shows up in versions that do not have the external pps input working. Even on the ones that *do* have a pps, it is not one that works well with the pps from a GPS. Simply put, that option is not worth spending money on. Manually adjusting an Rb against a GPS is a bit time consuming, but fairly easy to do.You need observations spread over days and you need to keep track of what you have done. Once adjusted it should run quite well for a long time. Weekly / monthly / quarterly checks should be all it needs. All modern Rb’s are based on firmware. different versions have different code in them. Swapping those files around is *not* often successful. Repair can easily involve parts that no longer are made. A lot of PRS-10’s simply get scrapped… ==== For $129 you can get a batch of 5 Temex Rb’s. They probably will need two dollars worth of caps replaced. You likely will find that one or two of them work “as is”. Bob > On Mar 11, 2016, at 8:50 PM, time...@metachaos.net wrote: > > Bob, > > After all of the excellent feedback here, my current thinking is that I can > get a parts / repair PRS-10 for somewhere near $150. There are several reasons > that this might be the best option... > > 1. It appears to be about the best that I can afford from what I have seen > of the testing that others have done. The HP 4065A is completely out of > the question. The only one I see available is $1340, plus shipping. A > brand new PRS-10 is $1495. So the choice there would be a very old unit > that might work for a few months or even a few years, but probably not > very long - with no parts available without using a parts unit. Or, a > unit nearly as good that has an expected life span of 20+ years and > which is still in production and would be under warranty for the first > year or so. > > 2. There are complete schematics available for the PRS-10 which gives me a > leg up on attempting a repair. There are also detailed circuit operational > descriptions in the service manual. That helps too. > > 3. Worst case, SRS has a repair service available at, at least in the past, > a reasonable cost (reportedly a fixed price of $200). Now you need an > RMA quote, but the price probably hasn't changed that much. If the > repair is something that I can't handle - e.g. the rubidium tube is bad, > then it can still be repaired for a total cost of around $350 to $400. > > In that case the total cost might be a bit higher than a working unit. > Or, perhaps not. The two working TSD12s that I see on eBay (apparently > the same as the PRS-10 except the lock flag is set to 3 instead of 1 and > which can be reset) are $285 and $512. And I don't see any working > PRS-10s at all. If this option is necessary then the cost would be > split, making it easier to swallow. And, SRS calibrates the unit when > they fix it at no extra cost (as long as it is requested before shipping). > > 4. The PRS-10 can handle the GPS synchronization simply by feeding the GPS > 1 pps signal to it. That eliminates a lot of secondary effort needed to > get the disciplining up and running. That would minimize both the cost > and effort. Control of both the PRS-10 and an LEA U-Blox can be done via > an USB to RS-232 adapter (or two). This feature is something that none > of the alternative rubidiums appear to have. > > 5. The PRS-10 has free windows software to assist in programming and > controlling it. > > The main negative is that I have never repaired an SMD product before. I don't > know if my skills are up to it. However, I can practice on junk before I > actually attempt to make a repair. And that is certainly a skill that will be > needed in the future! > > > Mike > >> HI > >> None of this is a simple slam dunk. > >> The 5065 has great ADEV numbers. In “as delivered” condition It has horrid >> TC and pressure sensitivity. It also is > 10X more expensive than a lot of the other devices. > >> The units that *can* be disciplined are rarely set up to do so properly off >> of a GPS source. If you want to run one as a 24/7 GPSDO, that may be a significant issue. > >> All of the “modular” Rb’s require heat sinking. For a reasonable lifespan, >> either a fairly healthy heatsink or something smaller plus a fan is called >> for. The impact on lifespan can easily be 10:1. > >> If your target is something like a microwave radio, many Rb’s are >> “challenged” in terms of phase noise and/or spurs. Some sort of cleanup will be needed for almost all of them. > >> The salvage process that some parts have been through is a bit brutal. >> That’s both good news and bad news. It lets you buy a “kit of 5” Rb’s to >> repair yourself for very little money. With luck you will get two or three >> working and still not have spent $200 on the batch (delivered). On the other >> hand, if you expect a really good unit when spending a lot more money … . you >> may not like the water damage (or whatever). > >> Lots to think about. > >> Bob > > > > > >>> On Mar 11, 2016, at 4:45 PM, Mark Sims <hol...@hotmail.com> wrote: >>> >>> Mark's Law of Rubidium Goodness... the bigger the box, the better it is. The HP5065A is one of the best units ever made. It can rival a cesium beam unit. The X72 is a horrid little creature. >>> >>> >>> I would also go with the M100 / FRK units. The LPRO an FE56xx units were designed for telecom use and meet the specs required of them and low cost. The M100 and FRKs saw a lot of use in military systems. >>> >>> Which one you choose is best determined by your budget, applications, and requirements. A noisy little X72 could be just fine, or you may need the beastly HP5065. >>> >>> >>> >>> >>> >>> >>> _______________________________________________ >>> 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. > > > > -- > Best regards, > Timenut mailto:time...@metachaos.net > > _______________________________________________ > 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.