[time-nuts] Choke Ring Pictures

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Mar 15 23:27:31 UTC 2010


Which antenna performance metric do you have in mind?
There are several, some of which are considered in the paper:
http://www.novatel.com/Documents/Papers/effectofantenna.pdf

Since the topography surrounding the antenna, its height and location on 
the Earth all affect measured performance any comparative measurements 
should use the same receiver and antenna location.

Some estimates for the effect of multipath on code phase receivers can 
be found:

http://bbcr.uwaterloo.ca/~wzhuang/papers/iee95_gps.pdf 
<http://bbcr.uwaterloo.ca/%7Ewzhuang/papers/iee95_gps.pdf>

Since the better timing receivers use carrier phase smoothing of the 
code phase timing, both the carrier phase and code phase performance of 
the antenna are important.

A phased array antenna like the one in the following papers may provide 
better performance than alternative antennae:

http://www.navsys.com/Papers/0001002.pdf


http://www.congrex.nl/07c12/papers/day1_s1_paper05_Konovaltsev.pdf

Some measurements with geodetic antennae:

http://www.fig.net/pub/fig2008/papers/ts05g/ts05g_03_eventzur_shaked_2816.pdf

Comparison of code phase and carrier phase time transfer:
http://tycho.usno.navy.mil/ptti/ptti2004/paper41.pdf

Bruce

WarrenS wrote:
> Brian wrote:
>
>> "There were also comments about surveying and timing antennas."
> Those may of been from me, unsuccessfully trying to make a point of 
> the difference between what is 'Best' and what is 'GOOD enough'.
>
>> "about every national timing laboratory uses choke ring antennas.   
>> ... for timing stability reasons."
> Then again they also have multiple CS and Just their Antenna budget is 
> likely more than the annual income of most time nuts.
> Can you do a test to show IF there is ANY improvement for the AVERAGE 
> time nut when compared to a well setup (Tbolt) GPSDO using a TacoSalad 
> antenna?
>
> Would be interesting to see a plot of cost vs. performance for the 
> various antenna types,
> Scaled to show the performance improvement that the average Time nut 
> would see.
> The TacoSalad antenna, originally cost me a total of $7.95, And took 
> under 30 seconds to build.
> That cost should be discounted because those parts had been considered 
> just throw away junk up until now.
>
> ws
>
> **********************
>
> ----- Original Message ----- From: "Brian Kirby" 
> <kilodelta4foxmike at gmail.com>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> Sent: Monday, March 15, 2010 2:09 PM
> Subject: Re: [time-nuts] Choke Ring Pictures
>
>
>> Dr. Clark passed on a tip that I used.  Put the funnel in a microwave 
>> oven and run it and see if the funnel warms up.  If it warms up, you 
>> do not use it.  I do not know what type of plastic the funnel was 
>> made out of; it was white, semi-transparent.
>>
>> There were also comments about surveying and timing antennas.  If you 
>> investigate about every national timing laboratory uses choke ring 
>> antennas.  Some enclose the antenna unit and they temperature control 
>> it. They do this for timing stability reasons.
>>
>> The commercial timing antenna is bullet shaped and is operated 
>> without a ground plane.  They are patch antennas.  When there is not 
>> ground plane, the antenna picks up best from the overhead and less 
>> towards the horizon. These antennas usually have a lot more gain 
>> (30-50 db vs most normal antennas in the 15-25 db range).
>> Also in surveying, we cut off the horizon at 15 degrees in software.  
>> A free Army Corp of Engineering manual on GPS Surveying is at 
>> http://140.194.76.129/publications/eng-manuals/em1110-1-1003/toc.htm
>> The main difference in surveying and timing is in surveying they use 
>> the carrier phase method, were in timing most use a solution derived 
>> from the processing of the coarse acquisition code, in were the 
>> receiver is in a fixed over-determined position .  Some timing labs 
>> are using carrier phase method, when they need more resolution.
>>
>> Brian - KD4FM
>>
> ****************
>>> warrens wrote:
> ...
>>> Preliminary results for the Taco Dish GPS antenna as an indoor 
>>> antenna are  looking good.
>>> Certainly worth considering if your GPS antenna is stuck indoors, 
>>> 'Out of the rain in the living room'.
>>> I find it best to rise it up near the ceiling such as on an upper 
>>> shelf with nothing above it.
>>> It would be hard to tell the difference between the GPSDO 
>>> performance obtained from this or the Best outdoor antenna if using 
>>> a Tbolt set to the  standard default settings.
>>> Picture attached
>>>
>>> ws
>>>
>> **************
>
>
>
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