I really don't care about the 1024 week roll over. My only concern is the 10
MHz stability. I have my frequency counter, spectrum analyzer, my 8VSB
analyzer and my network analyzer locked to 10 MHz. I am using Belden 9913
cable for my antenna feed and I am reluctant to go to LMR type cable Sent from
my Verizon, Samsung Galaxy smartphone by Morse code.700.00
-------- Original message --------From: [email protected] Date: 3/2/22 9:30 PM
(GMT-08:00)77To: Discussion of precise time and frequencyuhuu8u7 measurement
<[email protected]> Subject: [time-nuts] Re: Stability question Hi
Jack.At work I had to bring GPS signal to one of our labs, which is in the
middle of a building with no rooftop access or nearby window. The only I was
able to do it was to bring a long run of LMR400 cable from my rooftop antenna
on top of the building which connects to a GNSS splitter amplifier in the
middle of the path; and then another long LMR400 cable connected to a second
splitter and from that second splitter I distribute the GPS signal to the
clocks that sync our lab equipment. The total cable run from the antenna to the
first splitter is 60 meters (196 feet). The cable from that first splitter to
the second splitter is 70 meters (229 feet), and at the output of the second
splitter I have cables from 5 meters to 25 meters to bring the signal to each
clock. Even with this far from optimal setup I have not experienced
insufficient signal level or signal loss problem.That being said, I had
problems with two older Datum ExacTime 6000 and 6010 clocks that would take
forever to lock or receive only 2 or 3 satellites. They also were affected by a
GPS epoch problem. So I attempted to cure their problems with a GPS receiver
upgrade made by a French company called HEOL designs :
https://www.heoldesign.com/, the exact product is :
https://www.heoldesign.com/N024-GPS-receiver-board-for-Tymserve-2100?lang=en .
With the receiver upgrade the long lock delay and intermittent signal loss
problems disappeared, and the epoch rollover bug was cured, BUT although the
clocked was locked and correcting the "LOCK" LED was never on. It seems that
the upgrade board is fully compatible with the TimeServe 2100 but only
partially compatible with the ET6000.So I junked the two ET6000 and replaced
them with more recent vintage clocks and all is OK since I installed the
replacement clocks. For some strange reason clocks of similar vintage as the
ET6000 always synced OK and they still sync perfectly, like an ancient TrueTime
NTS-100i.Of course this is my experience and things might be different for
you.ClaudeLe 02/03/2022 18:49, Jack Davis a écrit :> CAUTION: This email
originated from outside your organization.> Exercise caution when opening
attachments or on clicking links from> unknown senders.> > > > > I have a Datum
Exactime ET-6000TCXO that I use to lock all my test> equipment to 10 MHz. My
GPS antenna is approximately 200 feet from> the receiver and I have
intermittent GPS signal levels and associated> unlocking of my ET-6000TCXO. I
have tried using bigger less loss coax> cable but its just not enough to make
it reliable.> > > > I see there is a Symmetricom Kit 142.6150 consisting of a
model> 140-615 GPS antenna / downconverter and a model 150-615 upconverter>
available to allow longer runs of coax cable. From what I can tell> there is a
local oscillator in the antenna that down converts the> 1,575.42 MHz GPS signal
to 4.092 MHz for lower cable loss. The up> converter on the receiver side
apparently another local oscillator> that up converts the 4.092 MHz IF to
1,575.42 MHz.> > > > My question is: will the two local oscillators and the up
and down> conversion cause phase noise or frequency instability of the GPS>
signals into my ET-6000TCXO? It does have some sort of flywheel> correction
internally but is it enough to keep the 10 MHz timebase> stable?> > > >
Thanks,> > Jack K6YC> > _______________________________________________> >
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