BPSK Receiver & GPS Antenna siting
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
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@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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and follow the instructions there.
Hi
A PLL locks to phase. If the phase switches by 180 degrees, the phase tracking switches signs. There's no way to track that. You either need to double the frequency (and thus eliminate the modulation) or demodulate the signal and lock to the result. If you simply put up a real narrow filter and hit it with continuous 180 degree phase shifts, the output will be nothing at all…
Bob
On Sep 27, 2012, at 7:11 PM, johncroos@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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and follow the instructions there.
You cannot put a narrow filter before the squarer for reasons previously
cited. In a low S/N area, squaring just makes matters worse wrt dynamic
range and clipping.
-John
==========
Hi
A PLL locks to phase. If the phase switches by 180 degrees, the phase
tracking switches signs. There's no way to track that. You either need to
double the frequency (and thus eliminate the modulation) or demodulate the
signal and lock to the result. If you simply put up a real narrow filter
and hit it with continuous 180 degree phase shifts, the output will be
nothing at all
Bob
On Sep 27, 2012, at 7:11 PM, johncroos@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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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On 9/27/12 4:34 PM, Bob Camp wrote:
Hi
A PLL locks to phase. If the phase switches by 180 degrees, the phase tracking switches signs. There's no way to track that. You either need to double the frequency (and thus eliminate the modulation) or demodulate the signal and lock to the result. If you simply put up a real narrow filter and hit it with continuous 180 degree phase shifts, the output will be nothing at all…
that's the whole thing about the inphase arm on a Costas loop.. that
gets multiplied by the phase error signal from the quadrature arm and
fixes the sign flip from the modulation.
Until I move into the house I'm getting I'm in a rental condo where absolutely
no antennas are permitted. It's a building and I'm on the 4th floor so have
done things like ran a very thin wire out one window to a far one, a wire with a
weight nearly to the ground, a rather long wire (#26 stranded copperweld) to a
far fence (at night), the Tbolt antenna clamped to my railing, and a mil type
multisection vertical clamped to said railing (also at night). Been here for a
couple of years and nobody's said a word, yet I've seen letters go out to
everyone about christmas decorations that were visible through windows. The
roof is locked but if I were to live here longer I would find a way up there and
feed a coax or three through the 1" PVC conduit which carries the thermostat
cable up to the A/C unit up there for my unit and have a blast with it.
Peter
On 9/27/2012 7:20 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@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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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Hi
Ok, to try to bring this back together.
There is indeed a valid Time Nuts need for something other than GPS. In reality there are many reasons. One that has not been mentioned is to check on the validity of your long term GPS time estimate Small errors that accumulate can be a really nasty thing …
If you live in the mainland US, there aren't a whole lot of alternatives to WWVB. Propagation is a reality that no amount of wishing will eliminate. HF isn't going to do you much good. Other LF signals just don't get here in any sort of useful condition.
The only rational way to get time information off of WWVB is to look at carrier phase over many days. We have decades of information about that. Unless they implement a fancy modulation scheme (which they very much have not) we are stuck with phase.
Making this all happen (or not) with legacy gear is an independent issue of the basics above. I believe that if you can extract phase by some technique, you can re-broadcast a signal that the old gear will work with. Maybe it's easier that that, I hope so, but have not proven that by doing it.
IF you want to simply do a new phase tracking receiver, there are a lot of bits and pieces you can use. None of them are terribly expensive. The "radio" part of the system (not the antenna, not the frequency standard, not the other boxes that input to the system) likely can be done for < $50 in raw parts. Weather that's a $5,000,0000 receiver or a $200 receiver depends on your markup.
Back when I bought them new, none of the legacy WWVB receivers cost $200. I don't remember any of them being much under $2,000. Would I pay $2,000 for one today? Nope, no more than I'd pay the same for a Loran-C receiver. Just for the record, I wouldn't pay $2,000 for a GPS either.
Would I dive into a receiver project before we see the patent filings? - no. I'm not independently wealthy. Financing the challenge(s) to the likely stupid series of patents isn't something I want to fund. Easy or hard technically has nothing to do with it. It's not worth going broke for ….
Bob
On Sep 27, 2012, at 7:59 PM, Jim Lux jimlux@earthlink.net wrote:
On 9/27/12 4:34 PM, Bob Camp wrote:
Hi
A PLL locks to phase. If the phase switches by 180 degrees, the phase tracking switches signs. There's no way to track that. You either need to double the frequency (and thus eliminate the modulation) or demodulate the signal and lock to the result. If you simply put up a real narrow filter and hit it with continuous 180 degree phase shifts, the output will be nothing at all…
that's the whole thing about the inphase arm on a Costas loop.. that gets multiplied by the phase error signal from the quadrature arm and fixes the sign flip from the modulation.
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
Bob,
Thanks for the nice, concise, summary of the screwing the new WWVB format
will inflict on the timing community, especially because LORAN-C is dead.
The only "benefit" to the NIST/XW scheme I can see is creating a monopoly
for Xtendwave in precision TOD marketplace for those not relying on GPS.
When, due to governmental action, people are thrown out of a job, the
government often funds millions and millions in "retraining",
"outplacement" and other forms of aid.
IMO, the very least the government, NIST specifically, could do is provide
a vetted design so that the installed base of receivers will continue to
function.
YMMV,
-John
===============
Hi
Ok, to try to bring this back together.
There is indeed a valid Time Nuts need for something other than GPS. In
reality there are many reasons. One that has not been mentioned is to
check on the validity of your long term GPS time estimate Small errors
that accumulate can be a really nasty thing
If you live in the mainland US, there aren't a whole lot of alternatives
to WWVB. Propagation is a reality that no amount of wishing will
eliminate. HF isn't going to do you much good. Other LF signals just
don't get here in any sort of useful condition.
The only rational way to get time information off of WWVB is to look at
carrier phase over many days. We have decades of information about that.
Unless they implement a fancy modulation scheme (which they very much >
have not) we are stuck with phase.
Making this all happen (or not) with legacy gear is an independent issue
of the basics above. I believe that if you can extract phase by some
technique, you can re-broadcast a signal that the old gear will work
with. Maybe it's easier that that, I hope so, but have not proven that
by doing it.
IF you want to simply do a new phase tracking receiver, there are a lot
of bits and pieces you can use. None of them are terribly expensive.
The
"radio" part of the system (not the antenna, not the frequency standard,
not the other boxes that input to the system) likely can be done for
$50 in raw parts. Weather that's a $5,000,0000 receiver or a $200
receiver depends on your markup.
Back when I bought them new, none of the legacy WWVB receivers cost
$200. I don't remember any of them being much under $2,000. Would I pay
$2,000 for one today? Nope, no more than I'd pay the same for a Loran-C
receiver. Just for the record, I wouldn't pay $2,000 for a GPS either.
Would I dive into a receiver project before we see the patent
filings? -
no. I'm not independently wealthy. Financing the challenge(s) to the
likely stupid series of patents isn't something I want to fund. Easy or
hard technically has nothing to do with it. It's not worth going broke
for
.
Bob
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@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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Put up a flagpole.
Randy, KI6WAS
Flagpoles need caps, right? A GPS antenna would be just perfect. And a
fiberglass flagpole could hide a significant HF vertical!
On 9/27/2012 10:24 PM, Randy D. Hunt wrote:
Put up a flagpole.
Randy, KI6WAS