Dear Edgardo,
On 10/21/2012 05:50 PM, Edgardo Molina wrote:
Dear Magnus,
Good morning. Welcome back! I hope you are enjoying typing at home again.
a. I just downloaded TimeLab. What a nice pice of software! Now I am ready for
some action.
Great. Do enjoy.
b. Regarding your comment on the TBolt as a close UTC source, I just finished
my first approach for my thesis GPSDO using the TBolt module. I still have to
master the use of Lady H. to get the best out of it. I have only been using
TBolt monitor software while I gain experience with it.
Tbolt + Lady Heather is a good combo.
c. As per our last comments on instrumentation for phase and time
interval measurements, I decided first to get an affordable unit such
as the 53132A with the Prologix GPIB adapter. Afterwards I am not
moving my finger from pointing to an SR-620 as a dedicated unit for
time interval and phase measurements. Until now I feel blind in terms
of measuring resources and technics. I must put some attention to it.
Once you are up to 5370, 53132A or SR620 level, you won't gain very
much, unless you go for a Wavecrest DTS.
For "deep" measurements, the TimePod with cross correlation and best
current practice in hooking it up will get you far more knowledge. It
will set you back, but it is amazing what you can measure in the home
lab with one of these. Especially since you can do real phase-noise
measurements, which the counters isn't at all suited for.
d. Your clarification of the use of Phase Shifters is welcome. I can
see the need for them to work with time scales and the differences
among the old and new Cs and Rb standards.
BTW, the term is "phase stepper".
e. Yes, you are right. They are currently using the Novatel antenna.
How different in performance is the Novatel 700 pin-wheel GPS antenna
compared for a regular amplified GPS unit such as the Symmetricom
52532A or the legacy HP units? Is it a matter of gain? Or radiation
pattern characteristics?
The Novatel 700 pin-wheel has significantly better multipath suppression
than many of the other antennas. It behaves similar to a choke-ring, and
the benefit of using choke-rings compared to simpler antennas has
already been tested and it was found that choke-ring antennas has
significant suppression of multipath and hence cause a stabler phase of
the timing receiver. As I recall this have been tried out using the
Tbolt and Lady Heather, and using the averaging mechanism.
Regarding the VP Oncore receivers I recall a comment from them
praising those receivers for both amateur and pro work. I haven't got
one yet, but certainly planning to do so. Dr. Levine commented that
the older units are better made and so, better performing. How can I
tell the difference? I have seen several variations on the used market.
There used to be more documentation on the Motorola range of GPS
receivers and chips. Would love to get collected.
f. A warm welcome to the new Atlanta member. Has he posted yet?
Just as me he was only in Atlanta for the meeting, and I haven't seen
him posting yet.
Thank you as always.
You are welcome.
Cheers,
Magnus
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