Don wrote:
This is typical for an underdamped second order servo. The oscillation
is the penalty for a shorter settling time. A critically damped system
would not oscillate, but approach the final value smoothly in a slightly
longer time. It may have been designed for a slight overshoot...
Ah. That seems right, Charles, going by the behavior. In that case, what
and where is the reference for the heater servo? The ambient
temperature? Not too wise a choice, but what else? So it may be that the
temperature is the controlling element but it, too, is an open system?
It can be open, too,
If I still have it, I'll take a picture of the 1992 i salvaged the
keyboard from. I was told it had
2 KW @ 700 MHz applied to it.
They do not make very good dummy loads.
-pete
On Tue, Dec 20, 2011 at 11:31 AM, Don Latham d...@montana.com wrote:
Ah. That seems right, Charles, going by the
Don wrote:
In that case, what and where is the reference for the heater servo?
It will be a voltage or current, suitably regulated and
conditioned. The temperature sensor's signal will be (or will be
converted to) a voltage or current that is compared to the reference
voltage or current.
Hi Ed,
my mistake, the test started from cold, but the curve I've posted starts at a
certain midnight. For completeness, the very initial warm-up is missing in the
curve. Checking my archive, I see that the test started the previous day around
02:22 pm and the reading was 3 mHz higher, and I
Antonio,
I suspected something like that.
I realized that I've never done a similar test so I'm correcting that
now. Both the oscillator and the counter have been off for some time -
days for the counter due to equipment rearrangements and months for the
oscillator. I replaced the 04E
I wrote:
I put one of mine in standby earlier this afternoon. I'll turn it
back on tomorrow afternoon and report the results.
(All results using 10 second gate): Yesterday, the 1992 had been
reading 000.00 E-3 stably for several days, and I switched it
to standby. After 16 hours in
The first reading after turn-on was about 370 Hz (yes, Hertz) low.
After 20 minutes the initial warm-up was complete and the reading was
238 counts (e.g. 0.238 Hz) above 10 MHz - well within the 1e-7 specification.
That's awfully similar to how mine behaves. I'm currently doing my annual
Charles,
My restart followed the same pattern as yours. Start high, go higher,
drift down, undershoot, recover. The start was 10 MHz +51 counts, rise
to +60 counts after 5 minutes, drift down to a minimum of +8 counts
after 90 minutes and recover to +11 counts after 10 more minutes for a
This is typical for an underdamped second order servo. The oscillation
is the penalty for a shorter settling time. A critically damped system
would not oscillate, but approach the final value smoothly in a slightly
longer time. It may have been designed for a slight overshoot...
Don
Ed Palmer
My mistake:
I wrote:
(peaks = PC has been turned on, dips = PC has been turned off).
Please read:
(dips = PC has been turned on, peaks = PC has been turned off).
Antonio I8IOV
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Well, the 1992, at least mine, is sensitive to rapid changes of the ambient
temperature, while ignores quite well the slow changes such as those due to the
cycling of the heating system of the house (which is well evident in the
recorded temperature of the LPRO heatsink).
And I see that the
On 12/16/2011 5:57 PM, Charles P. Steinmetz wrote:
Larry wrote:
However, while counting the 10 MHz from my HP Z3801A and displaying
0.01 Hz resolution on my 1992, I can rap very smartly indeed with my
knuckles on the outside of the counter case (anywhere) and not change
the displayed count.
I haven't seen a capacitor with detents. Could the fine adjustment be a
multi-turn pot? I've seen detents with those. I looked at mine but
couldn't tell. A pot would mean voltage control. Maybe we could build
a GPSDC (GPS Disciplined Counter). Yes, I'm kidding. I think.
Ed
On
measurement
Subject: Re: [time-nuts] My Racal-Dana 1992
The fine adjustment has detents -- if you adjust it slowly, you can count
the clicks.
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The fine frequency control on my 1992 with 9462 has a range of 1 Hz.
It is multiple turns end to end, which I did not count.
There is noticeable friction on the fine freq adjustment.
The slight end play (backlash) between screwdriver and the adjustment makes
fine adjustment difficult.
It has not
Ed wrote:
My 04E must be less stable than yours. I was monitoring a fully
warmed-up Efratom FRK rubidium and saw a drift of ~ 0.04 Hz (i.e. 40
counts) over two hours after I turned on my 1992 from standby. Are
more than one type of oscillator used for option 04E? Mine is a model 9462.
Chuck wrote:
It has not occurred to me that either the coarse or fine adjustment
has detents.
Could this be the friction you mention? If you turn the fine
adjustment very slowly, can you detect regular clicks (feels almost
like stiction and release, but very regular/periodic)? (I have not
On 12/18/2011 12:00 PM, Charles P. Steinmetz wrote:
Ed wrote:
My 04E must be less stable than yours. I was monitoring a fully
warmed-up Efratom FRK rubidium and saw a drift of ~ 0.04 Hz (i.e. 40
counts) over two hours after I turned on my 1992 from standby. Are
more than one type of
Ed wrote:
Agreed. But it was annoying to leave it in standby mode and then
still have some drift. At first, I thought the drift was due to the
rest of the unit warming up. I was quite surprised when my tests
showed that the drift was 100% due to the oscillator. Using an FRK
as an
Charles,
I don't know the answer to that question. Since it's a thermal issue,
it's a question of how long does it take for the temperature to
stabilize? 24 hrs. should be lots of time. I'd check it before going
to bed. A quick turn-on and measure won't raise the temperature much
and
18, 2011 12:00:58 PM
Subject: Re: [time-nuts] My Racal-Dana 1992
There are actually two Racal part numbers that you sometimes see in
documentation as being used for Option 04E -- 404386 and 454879. The
9462s in the US military contract 1992s that I have seen (pretty much
all of the 1992s one
As a contribution to this discussion, I attach a 17-day trace recorded with one
of my 1992s on Feb 2008. The counter was counting a LPRO Rb. The test started
from cold for both sets. Gate time was 10 sec.
The 1992 is the 02M/04E military.
Antonio I8IOV
attachment: racal1992.JPG
If the variable capacitor in question has ball bearings, it's probable that the bearing is
a bit tight and the races have indented. This gives the effect of a detent.
On 2011-12-19 01:17, Ed Palmer wrote:
I haven't seen a capacitor with detents. Could the fine adjustment be a
multi-turn pot?
Hi Antonio,
Between you and Charles, I'm getting the feeling that my 04E oscillator
is defective. Yours only moved 15 counts over a period of days from a
cold start. Mine moved 40 points in two hours from standby. I think I
have some testing to do.
Thanks,
Ed
On 12/18/2011 6:01 PM,
On 12/16/2011 2:31 PM, gandal...@aol.com wrote:
Hi David
It's part of the resolution settings, whereby you alter the number of
displayed digits using the up down arrows, holding the up arrow for over two
seconds will shift the display left and increase the gate time so you
effectively get a 10
It turns out that I unfairly maligned the 1992 (and the 9462
oscillator, option 04E) when I accused it of poor oscillator
settability. I was inspired by the recent discussions to have
another crack at mine, and they can, in fact, be set very
accurately. One of mine has been reading
Has a 9462 oscillator module in it.
I've been fooling with little C hacks to make freq and phase
measurements via GPIB.
In my desire to super-tweek the timebase I discovered that small
adjustments take
many minutes to settle down. It's like herding cats.
I noticed that physical shocks
Forgot to mention, each point is slightly more than 1 second.
On 12/16/2011 03:19 AM, Chuck Forsberg WA7KGX N2469R wrote:
Has a 9462 oscillator module in it.
I've been fooling with little C hacks to make freq and phase
measurements via GPIB.
In my desire to super-tweek the timebase I
Chuck, I have a Racal 1992 with exactly the same government label on its
side as in your picture, except that my ink-stamped warranty date is a
few days later than the date on your counter/timer. These must have come
from a large government contract order.
However, while counting the 10 MHz
I bought a 1992 a few years ago and I've been quite happy with it. It
does have a few quirks, of course. Some good, some bad.
1. You can get a 10 sec. gate time and therefore .001 Hz resolution at
10 MHz by holding the 'up arrow' key for about 2 sec. It's in the
manual, once. If you
-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf
Of Ed Palmer
Sent: 16 December 2011 18:09
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] My Racal-Dana 1992
I bought a 1992 a few years ago and I've been quite happy with it. It does
have a few quirks
Hi David
It's part of the resolution settings, whereby you alter the number of
displayed digits using the up down arrows, holding the up arrow for over two
seconds will shift the display left and increase the gate time so you
effectively get a 10 digit display with the left most digit
Larry wrote:
However, while counting the 10 MHz from my HP Z3801A and displaying
0.01 Hz resolution on my 1992, I can rap very smartly indeed with my
knuckles on the outside of the counter case (anywhere) and not
change the displayed count. Further, my counter seem insensitive to
orientation
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