[time-nuts] Frequency standard

[Bob kb8tq]

Hi

So what’s the downside to all this:

Keeping an OCXO (and counter) turned on 24 hours a day, 365 days a year burns power. If you
also live in air conditioning land, you pay even more to get rid of the heat from the power. 
Sit down and do the math. You likely will find this is not as cheap as it first seems. 

A GPSDO running over the same time period also chews up energy. It might use less, it might 
use more. A lot depends on exactly which model of each. Same thing on an Rb while it is running. 
(note that sneaky qualifier).

The neat thing about the Rb is that you can turn it on today and it will be doing pretty darn well tomorrow.
Do your measurements and shut it down again. Since cost isn’t very different between a GPSDO and
an Rb, the comparison is not too far fetched. 

If you happen to play with radios, having a 10 MHz reference will get into things. Same may be true of 
harmonics of 10 MHz. How much and how often it is an issue depends on a lot of things. Turning 
the whole thing off eliminates the problem. 

Regardless of what you are running, keeping it on 24/ 365 will cause some wear on some parts of it. 
That’s just the way MTBF’s work out. Turning on and off also creates issues so there is no magic way
to eliminate failures. It is a pretty good bet that a device that is off 99.99% of the time will live longer than 
one that is on power all the time. 

So no, it’s not a one size fits all sort of thing. The solution that makes sense in one case will be 
needlessly expensive in another case. If it’s a focus of a hobby, that is different. If it is just another 
tool in the tool chest, no need to overspend. Save the hard earned cash for something else. 

Bob

> On Jan 26, 2019, at 4:31 PM, Bob Albert via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Well you are right that I am bit far from JPL.  I used to work there.  But I am impressed with the number of replies and the number of suggestions.  I am still mulling over what will work for me.  Apparently this group is made up of helpful and knowledgable guys who aren't afraid to share their expertise.
> I don't have a microwave receiver.  I don't even know what frequency range I might want to hear.  Yes there are amateur beacons but the only one that stands out in my mind is the one in Long Beach on 10 meters.  Given its target frequency, I am a bit at a loss as to how to make use of its accuracy.  I could use a local signal generator as a transfer oscillator and measure it while trying to hold it on zero beat with the beacon.
> Great stuff but I do have gaps in my knowledge that I'd love to close.
> Bob
>    On Saturday, January 26, 2019, 1:00:23 PM PST, jimlux <jimlux at earthlink.net> wrote:  
> 
> On 1/26/19 10:43 AM, Bob Albert via time-nuts wrote:
>>   Dave, thanks for the info.  I am, as I have said, money limited to the point where most solutions won't work for me.
>> My counter is an HP 5328A I belive.  Not the top of the line but with care it can do a decent job.  It's oscillator is the standard oven job.  When I got it, it was almost spot on but it's been a while and I'd like to reset or at least recheck it.  It's good enough that it can watch other oven oscillators drift, such as the one in my 8657B generator.  I mean, who is crazy enough to sit for hours watching a display progress more and more slowly toward some monte carlo frequency?
>> Anyway it's all in fun for me and I have no real need for this precision.  And I know how close my transceiver must be to be 'on frequency' and it certainly is fine with no intervention
> 
> If your email name is your zipcode in North Hills, then you're a bit far 
> away from JPL to pick up the omnipresent 10MHz (and harmonics) that's 
> leaked/radiated everywhere on lab. For most of the leakage, it's 
> probably based on either local Rb or GPSDO in the specific lab, or 
> locked to the lab's maser distribution.  Generally fairly close to "dead 
> on" ( a very narrow spectrum analysis from a whip antenna is fascinating..)
> 
> It's an idea..
> 
> If you have microwave receive capability, several of the amateur beacons 
> in the Los Angeles area are now locked to a GPSDO - I don't know which 
> ones off hand, but an email to someone in the SBMS (San Bernardino 
> Microwave Society) would probably be useful.  For that matter, their 
> monthly meetings often have someone there with a Rb source that you 
> could use to calibrate, or arrange to meet up with.
> 
> There's also some microwave shootouts in the area where everyone goes to 
> measure their noise figure and antenna gains, and I guarantee that at 
> one of those, *someone* will have a high quality frequency standard.
> 
> 
> 
> 
> 
> 
> 
> 
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