[time-nuts] BPSK Receiver & GPS Antenna siting

J. Forster jfor at quikus.com
Fri Sep 28 14:38:14 UTC 2012


Welcome to:

Regulation Nation

-John

==============



> Hi
>
> Flag poles are prohibited.
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Randy D. Hunt
> Sent: Thursday, September 27, 2012 10:24 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] BPSK Receiver & GPS Antenna siting
>
> On 9/27/2012 4:20 PM, Bob Camp wrote:
>> Hi
>>
>> At least in my back yard, a 6' tall tripod would be very noticeable from
>> a
> number of directions. There are many others in similar situations. If I
> were
> to interpret the restrictions literally as written, an antenna that was
> inside the house, but visible through an open window is also a violation.
>>
>> Bob
>>
>>
>> On Sep 27, 2012, at 7:11 PM, johncroos at aol.com wrote:
>>
>>> Various comments -
>>>
>>> Hal mentioned SNR for the scheme I suggested. A PLL can be a coherent
> demodulator of arbitrary
>>> bandwidth. Thus the PLL at the output of the doubler can have a small
> bandwidth since at that point
>>> there is no PSK, it having been removed by the doubler. So given a
>>> stable
> VCXO you can probably get down
>>> to 1 Hz and thereby achieve a good SNR. There is a lot of stuff out
>>> there
> on phase tracking receivers
>>> that do exactly that. You know the frequency so the loop does not have
>>> to
> search far and the BW can be increased
>>> for acquisition and closed up for tracking.
>>>
>>> On writing reams of code - my point was that it is not required to used
> the admittedly more powerful software
>>> techniques to do this job - I noted that one reason to write reams of
> code is for the fun of it, this is after all
>>> a hobby.
>>>
>>> GPS Antenna Siting -
>>>
>>> Lets not make this so hard. Mine is at 6 ft elevation and is blocked to
> an elevation angle of 20 to 30 degrees by a house
>>> within 15 ft and a forest of trees. I have room and no restrictions but
>>> I
> also have severe thunderstorms - so the house
>>> plays lightning protect for the antenna. My T bolt tracks a Rb to
>>> better
> than 1e-12 over 24  hours with no serious 10 MHz phase bumps
>>> as plotted on a  strip chart recorder.
>>>
>>> Sooooo  -
>>>
>>> Put your antenna at 6 ft in back yard. Start out on a photo tripod -
>>> who
> is gonna notice?
>>> set up a t bolt at EL=5 AMU=0 Damping = 1.2 and Time Constant = 100
>>> sec.
>>> get the t bolt manual
>>> get Tbolt monitor
>>> get Lady Heather and read all that stuff.
>>>
>>> Run Lady Heather antenna survey (command SAS)  for at least two days -
> you get a map of signal level in dBc vs elevation
>>> Reset the Tbolt elevation mask to reject anything that is shown as
> blocked using the signal
>>> level map. Likewise experiment with the AMU setting to reject the weak
>>> =
> poor signals. Mine works good
>>> with AMU all the way up to 10 as fewer good satellites are better than
> lots of weak ones.
>>>
>>> The satellites are in high orbits so masking those below 25 degrees is
>>> OK
> and the AMU sets the acceptable signal
>>> level - at AMU 10 my setup throws out those below about 40 dBc - the
> strong guys go up to 50. This is a function
>>> of you antenna performance so some experimentation is required.
>>>
>>> -73 john k6iql
>>>
>>>
>>>
>>>
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>>
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> Put up a flagpole.
>
> Randy, KI6WAS
>
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