Walt, is your PRS-10 factory new, or just new for you?

The 20-25 minute initial lockup time seems awfully long,
and the 25 mHz frequency error (against what?) is
way high, unless the reference for this measurement is
off.

You've got me kind of worried.  I just took delivery of
a factory new PRS-10 a few days ago, but have been too
busy so far to fire it up.

I bought a PRS-10 surplus several years ago and it has
been fine except that it is surplus from the telecomm market
and does not include the PPS locking feature.  I also have
a CNS Clock II (GPSDO) which I use for a reference, but
its "GPS noise" level is much too high for its 10 MHz output
to be used directly.  I have been comparing its 10 MHz
output to the old Rb in a quadrature demodulator, viewing
the difference frequency output on a DSO in "roll mode",
so that i can see what's been going on for the past 14,000
seconds at a glance.  This arrangement has been quite
satisfactory for manual checking and tweaking the PRS-10
from time to time, but I'd been getting tired of having to
make the effort manually.  Thus my purchase of the brand
new PRS-10 with all the features.

My old PRS-10 started out being on frequency with the
tune voltage being set around 1.5 V, but over the last 7
years the required tune voltage has been drifting down-
wards and of late has been down around 0,7 V.

My aim in buying the brand new PRS-10 has been in
eliminating the need for manual attention to keep in on
frequency- I want to just turn on the "bubble machine"
and let it take care of itself for a long time thereafter.
The role of the PRS-10 in this play will be to serve as
a big "flywheel" to smooth out and reduce the "GPS noise"
on the CNS Clock II.  Time will tell, so to speak.

Dana

It is used, and appears to be a pull that has not been messed around with.
I am getting familiar with it in anticipation of buying more.  If it turns
out to be a dud, well, I am still getting some experience with Rb.

Yes, the 25-minute lockup time is rather long and suggests to me a unit
nearing its EOL.  New ones are, what, 5 minutes?  Some of the analog values
are near the lower limits specified in the user manual, and that has me
wondering.  More study is needed to find out how to assess the important
things (lamp intensity and varactor voltage?) and to see if PPS locking
works.

As for the +25 mHz error against the Z3805A GPSDO, I will eventually center
the external ref pot and see if the internal ref pot has enough range left
to bring the frequency down to 10MHz.  Or try the external voltage method.
If I am lucky I may find that it has simply never been adjusted.

As the St. Pauli Girl beer poster I had in the late 70s said, "You always
remember your first."

Walt

-----Original Message-----
From: Dana Whitlow via time-nuts time-nuts@lists.febo.com
Sent: Tuesday, February 11, 2025 12:14 AM
To: Discussion of precise time and frequency measurement
time-nuts@lists.febo.com
Cc: Dana Whitlow k8yumdoober@gmail.com
Subject: [time-nuts] Your "first" PRS-10

Walt, is your PRS-10 factory new, or just new for you?

The 20-25 minute initial lockup time seems awfully long, and the 25 mHz
frequency error (against what?) is way high, unless the reference for this
measurement is off.

You've got me kind of worried.  I just took delivery of a factory new PRS-10
a few days ago, but have been too busy so far to fire it up.

I bought a PRS-10 surplus several years ago and it has been fine except that
it is surplus from the telecomm market and does not include the PPS locking
feature.  I also have a CNS Clock II (GPSDO) which I use for a reference,
but its "GPS noise" level is much too high for its 10 MHz output to be used
directly.  I have been comparing its 10 MHz output to the old Rb in a
quadrature demodulator, viewing the difference frequency output on a DSO in
"roll mode", so that i can see what's been going on for the past 14,000
seconds at a glance.  This arrangement has been quite satisfactory for
manual checking and tweaking the PRS-10 from time to time, but I'd been
getting tired of having to make the effort manually.  Thus my purchase of
the brand new PRS-10 with all the features.

My old PRS-10 started out being on frequency with the tune voltage being set
around 1.5 V, but over the last 7 years the required tune voltage has been
drifting down- wards and of late has been down around 0,7 V.

My aim in buying the brand new PRS-10 has been in eliminating the need for
manual attention to keep in on
frequency- I want to just turn on the "bubble machine"
and let it take care of itself for a long time thereafter.
The role of the PRS-10 in this play will be to serve as a big "flywheel" to
smooth out and reduce the "GPS noise"
on the CNS Clock II.  Time will tell, so to speak.

Dana

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