[time-nuts] HP-5065A frequency adjustment advise and Common (all in) view GPS comparisons proposal.

Magnus Danielson magnus at rubidium.dyndns.org
Sun Oct 21 12:52:46 EDT 2012


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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