lists at cq.nu
Thu Feb 11 17:12:55 UTC 2010
The case of a rubidium acts as a magnetic shield. I would not recommend
operating one without the case or any of the internal shields and covers.
The rubidium physics package operates on the internal crystal oscillator
through a fairly narrow loop bandwidth. If the issue looks like microphonics
I would start looking at the OCXO and buffering first.
The physics package needs to heat up in order to do it's work. If you try to
cool it, the heaters will just draw more power to keep it hot.
With any standard, keeping the external environment constant is more
important than keeping it at one temperature or another. The first thing to
do is to eliminate drafts. The stuff will run a few degrees warmer, but it
will be more stable.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Raj
Sent: Thursday, February 11, 2010 9:47 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Vibrations
I will explore this issue tomorrow, 20:00 here now. I was just going
through a boyish thrill of fiddling with a Sony ICF-S10Mk2 and the amazing
numbers of AM stations it picks up.. maybe it can be used at 60Khz.. for 10$
it worth it !!
How about keeping he Rb cover open ? I measured the lamp housing at
110C and the rest at 60-70C. I dont intend to keep my units on all the time
but I dont feel good about anything running hot! Maybe a small slow fan
might help. I am fascinated by the blinking light inside at 1Hz and thats
not available on the DB connector. I did add a reverse polarity protection
by soldering a 2A diode between the center pin of the regulator and the +15
pin. I wish I can find a schematic and what else I can do with this gizmo!
73 Raj vu2zap
At 11-02-10, you wrote:
>I integrated a Symmetricom model X72 Rb into a Down East Microwave (DEMI)
>and it does experience microphonics. This was for a friends 10 GHz
transceiver used for portable work.
>So getting rid of the microphonics is important.
>Somehow I need to mechanically isolate the Rb from the chassis and still
have a heat sink.
>>While comparing a Rb FE5680 frequency reference with another RB or GPSDO I
find that tapping a Rb unit causes a sudden shift in the scope display
meaning the frequency has slightly shifted momentarily and locks back
steadily with a phase shift. This does not happen in another Rb FE5680.
>>Would something be loose I wonder ? Any experiences?
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