[time-nuts] Choke Ring Pictures

Bob Camp lists at rtty.us
Mon Mar 15 23:48:23 UTC 2010


Hi

The helix was the original "NBS" antenna for GPS. Lucent's antenna dates back to the early 80's. The patch came along later. There are some significant differences between them, few of which matter in normal time nut applications. 

It's pretty easy to translate surveying units into timing units as far as just the antenna is concerned. All you really need to know is the speed of light. For quick calculations 30 cm = 1 ns. If you are moving around an extra +/- 1 M with antenna X,  then you have ~ +/- 3.3 ns flopping around that you otherwise would not have. 

Bob


On Mar 15, 2010, at 7:12 PM, Brian Kirby wrote:

> And the Andrew , Motorola and Pansonic have patches....
> 
> Brooke Clarke wrote:
>> Hi Brian:
>> 
>> The Lucent bullet antenna has a quad helix antenna structure, photos at:
>> http://www.prc68.com/I/DAGR.shtml#Ant and scroll down,
>> or maybe faster go to:
>> http://www.prc68.com/I/DAGR.shtml#DC
>> and scroll up.
>> 
>> Have Fun,
>> 
>> Brooke Clarke
>> http://www.PRC68.com
>> 
>> 
>> Brian Kirby wrote:
>>> 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
>>> 
>>> 
>>> 
>>> Bob Camp wrote:
>>>> Hi
>>>> 
>>>> Any idea what the funnel was made out of? Some plastics aren't real great at
>>>> microwaves...
>>>> 
>>>> Bob
>>>> 
>>>> -
>>> 
>>> 
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>> 
>> 
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> 
> 
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