I can't do any antenna comparisons. The choke ring was at my house - I
now live in a apartment and the landlord allowed me to put a patch
antenna on the edge of the roof (and his rules are no external antenna -
got his permission before moving in).
I would expect the average patch antenna with a ground plane would be
good enough for any gps receiver as long as the antenna has enough gain
and transmission line loss is acceptable.
I showed the pictures, because somebody ask me about them a couple of
years ago and I forgot. And they were made for a multi path problem,
and it stopped it. The reason I made the other two was for testing
carrier phase surveying with the Motorola Oncore VPZ receiver. I was
able to get down to the inch level with these units - maybe if they were
commercial they may have done better. It was an experiment for myself.
As with any hobby, you can spend what you want, your choice.
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"
<[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
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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