[time-nuts] Choke Ring Pictures

[Brian Kirby]

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
>
> -