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" <kilodelta4foxm...@gmail.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts@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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