[time-nuts] antennas was Re: Common-View GPS Network

Chris Albertson albertson.chris at gmail.com
Thu Apr 18 03:01:47 EDT 2013


If I read the paper correctly you can skip the choke ring if you mount the
antenna on top of a 2 meter or longer mast.  Iron pipe comes on 10 foot
lengths.  The choke ring is for portable survey antenna that can't be
placed on tall rooftop masts.   I think a 2 meter pole on a roof pretty
much meets their criteria of multi path difference being over 10 meters.

I can see now why surveyers need the choke ring type antenna, because they
can not choose the location.  They need to place it where they need to
measure.  But timing is different, we can choose the best location which
would be two meters above the tallest object in the area.

The cake pan certainly would work.  This is not super critical.  They are
only blocking low elevation signals. and it would give you more option for
the location


On Wed, Apr 17, 2013 at 8:14 PM, Jim Lux <jimlux at earthlink.net> wrote:

>
> Javad has a bunch of choke ring theory..
> http://www.javad.com/jns/**index.html?/jns/technology/**
> Single-Depth%20Low-Multipath%**20Choke%20Ring.html<http://www.javad.com/jns/index.html?/jns/technology/Single-Depth%20Low-Multipath%20Choke%20Ring.html>
> http://www.javad.com/jns/**index.html?/jns/technology/**
> Choke%20Ring%20Theory.html<http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html>
>
> Their conclusion is you want the depth of the ring to be slightly more
> than 1/4 lambda.  lambda/4 for L1 is 1.87" so a 2" cake pan is just about
> the right size.
>

-- 

Chris Albertson
Redondo Beach, California


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