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Message |
Joe McElvenney
Guest
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 Posted:
Fri Apr 29, 2005 4:07 pm Post subject:
Rubidium Lamp Voltage |
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Hi,
Rubidium frequency standards based on the EFRATOM FRK modules
usually have the facility to measure 'Lamp Voltage'. Does anyone
know what is actually being measured here as the lamp is an
acorn-sized phial of gas with no internal electrodes? Lamp
excitation is, I believe, by induction so maybe this 'voltage' is
simply an analogue of some other process.
Thanks.
Joe - Possessor of an aging RACAL-DANA 9475.
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Dan Rae
Guest
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| Posted:
Sun May 01, 2005 12:35 am Post subject:
Re: Rubidium Lamp Voltage |
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Joe McElvenney wrote:
| Quote: | Hi,
Rubidium frequency standards based on the EFRATOM FRK modules
usually have the facility to measure 'Lamp Voltage'. Does anyone
know what is actually being measured here as the lamp is an
acorn-sized phial of gas with no internal electrodes?
|
It is the voltage of the output of the op-amp that amplifies the output
of the photocell that is being measured there. Approx 5 to 12V is
healthy, if 3 Volts, you need a new lamp.
good luck...
| Quote: | excitation is, I believe, by induction
79 MHz RF |
dr |
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Clarence_A
Guest
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| Posted:
Mon May 02, 2005 8:35 am Post subject:
Re: Rubidium Lamp Voltage |
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"Dan Rae" <danrae@verizonEXTRACTTHIS.net> wrote in message
news:vfSce.1523$nN.791@trnddc05...
| Quote: |
Joe McElvenney wrote:
Hi,
Rubidium frequency standards based on the EFRATOM FRK
modules
usually have the facility to measure 'Lamp Voltage'. Does
anyone
know what is actually being measured here as the lamp is an
acorn-sized phial of gas with no internal electrodes?
It is the voltage of the output of the op-amp that amplifies the
output
of the photocell that is being measured there. Approx 5 to 12V
is
healthy, if 3 Volts, you need a new lamp.
good luck...
excitation is, I believe, by induction
79 MHz RF
dr
|
Lamps are not free nor can they be installed other than in the
factory.
If there is Lamp voltage and your not getting lock, there is an
oscillator adjustment which you might try. Use only a
non-metallic adjustment tool and try tuning the pot a quarter turn
"counter Clockwise at a time. Wait a few seconds to see if you
get lock. then try again. If there is no lock by the time you get
to max, you can try "Clockwise" slowly, however If you reach less
than two turns to the end of travel the oscillator is DEAD.
Efratom was purchased by Datum, six years later it was sold to
Symetricon. They might still service it, but it is EXPENSIVE!
These oscillators were about %5,000 to $7,500 in small quantities
new!
Test-Equity some times has some refurbished to sell.
Dan, do you agree? Carolyn gave me the instructions!
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Joe McElvenney
Guest
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| Posted:
Tue May 03, 2005 12:35 am Post subject:
Re: Rubidium Lamp Voltage |
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Hi,
Thanks to the both of you for that information. In fact the
standard I have that contains the FRK-L is in good working order
and locks fine after a few minutes even though the lamp voltage
is down to 5.5. It is just that on the schematic, the EFRATOM
subassembly for the RACAL-DANA 9475 is shown as a simple block
and so far I haven't been able to run down a copy of the internal
circuit.
I have a spare surplus lamp arriving in a few days although
I've had to take it on trust that it doesn't have too many hours
on the clock. Unfortunately the mounting boss is slightly
different to mine but I hope to release the bulb from this and
get a new fitting turned-up. I am able to carry out basic
confidence checks against off-air standards and, as my
requirements are modest, the odd digit reduction in the 'n' of
'parts in 10^n' is not of concern.
As penance for my sins in a former life, I once had charge of
a calibration lab where the frequency sources were Rubidium
referenced. They were dumped when the cost of new lamps or trips
back to the manufacturer from the Middle-East became greater than
new GPS-disciplined oscillators.
Thanks - Joe |
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Clarence_A
Guest
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| Posted:
Tue May 03, 2005 10:28 pm Post subject:
Re: Rubidium Lamp Voltage |
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"Joe McElvenney" <ximac@btinternet.com> wrote in message
news:VA.000000f4.0041e4c6@btinternet.com...
| Quote: | Hi,
Thanks to the both of you for that information. In fact the
standard I have that contains the FRK-L is in good working order
and locks fine after a few minutes even though the lamp voltage
is down to 5.5. It is just that on the schematic, the EFRATOM
subassembly for the RACAL-DANA 9475 is shown as a simple block
and so far I haven't been able to run down a copy of the
internal
circuit.
I have a spare surplus lamp arriving in a few days although
I've had to take it on trust that it doesn't have too many hours
on the clock. Unfortunately the mounting boss is slightly
different to mine but I hope to release the bulb from this and
get a new fitting turned-up. I am able to carry out basic
confidence checks against off-air standards and, as my
requirements are modest, the odd digit reduction in the 'n' of
'parts in 10^n' is not of concern.
As penance for my sins in a former life, I once had charge of
a calibration lab where the frequency sources were Rubidium
referenced. They were dumped when the cost of new lamps or trips
back to the manufacturer from the Middle-East became greater
than
new GPS-disciplined oscillators.
Thanks - Joe
|
There were no schematics released! You will be unlikely to find
one. I only saw schematics because I quoted the upgrade of the
FRK, but there was no contract. I had to return the one schematic
I had, and Carolyn said it was an earlier version anyway. Carolyn
was the one who assembled and tested the units for compliance for
eleven years. |
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Ray
Joined: 18 May 2005
Posts: 1
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| Posted:
Wed May 18, 2005 2:56 am Post subject:
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Joe,
You probably will not get schematics because all their info is proprietary.
They are very secretive.
Even if you get a bulb, there is a lot you have to do that is criticle to get the unit locked. The improper reassembly alone can cause the unit not to work. The adjustment that you can access is to correct for frequency drift.
Sometimes you can get lucky and get the unit to lock if you turn the pot.
It takes a tech. a couple of months just to learn how to tune a rubidium
oscillator. I remember Carolyn, she was very knowlegdeable.
Good Luck, Ray |
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