Best location for a GPS antenna...?
Time-Nutters--
My workshop is surrounded by tall trees (70 to 80 ft). There
is no easy way to place my T-Bolt antenna above the tree-top
foliage. Since choke-ring antennas do not provide much benefit
for dealing with multi-path that originates from directly above
the antenna I have considered putting the antenna on a 10-ft
pole and mounting the pole in the top of the nearby trees so
as to have the antenna just above the tree-top foliage.
However, here in north-central Florida lightning is a serious
problem. In the 12 years we have lived here, 3 trees have
been hit within 75 meters of my workshop building behind
my house.
Here is a DropBox link to a map of lightning-strike-days
in USA locations:
http://dl.dropbox.com/u/60102282/Lightning%20Isokeraunic%20map.JPG
I have a number of VHF and UHF antennas mounted on my
workshop building but when not in use, they are kept
disconnected where they enter the building.
I have thought about finding some way to bring the GPS
RF signal into my workshop via an optical fiber interface
and sacrifice the RF to optical fiber interface if lightning
strikes it in a treetop but have not found a way to implement
this idea.
Two years ago lightning struck a neighbor's TV antenna
mounted on a pole attached to the side of his house and
started a fire in one of their 2nd floor bedrooms which
did a lot of damage before it was put out. The tower
was well grounded and the coax leading into the room
was fed through a grounded lightning protector but none
of these precautions prevented the fire from the lightning
strike.
Any list folks have ideas on this?
Mike Baker WA4HFR
Gainesville/Micanopy, Fla
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
For example, locate the antenna as suggested. Locate the t'bolt in a
suitable enclosure/location either at the building entry or even at the
bottom of the tree. Protect it as well as you can, take best practices for
grounding, etc, but expect to loose one every few years. Maybe put one in
the spares collection. Then take the output of the t'bolt, run through
appropriate electrical to fiber conversion, and feed that to the
distribution amplifier. don't use metal jacketed fiber or metal conduit. A
mistake I have seen made, to great expense.
The issue is that this treats the t'bolt as a sacrificial item. I would
contend that, at a cost of $80-90, you could spend far more time and effort
trying to isolate, amplify, correct, and bias the antenna than that is
worth. Effort and gear that would need to be replaced every time it gets
blown up. My admittedly small direct experience is that lightning arrestors
don't protect from near or direct strikes, just from 'close' strikes.
Just $0.02 from a part of the world that doesn't get zorched nearly as
often. :)
Bob
KI2L
On Wed, Apr 11, 2012 at 8:50 AM, Michael Baker mpb45@clanbaker.org wrote:
Time-Nutters--
My workshop is surrounded by tall trees (70 to 80 ft). There
is no easy way to place my T-Bolt antenna above the tree-top
foliage. Since choke-ring antennas do not provide much benefit
for dealing with multi-path that originates from directly above
the antenna I have considered putting the antenna on a 10-ft
pole and mounting the pole in the top of the nearby trees so
as to have the antenna just above the tree-top foliage.
However, here in north-central Florida lightning is a serious
problem. In the 12 years we have lived here, 3 trees have
been hit within 75 meters of my workshop building behind
my house.
Here is a DropBox link to a map of lightning-strike-days
in USA locations:
http://dl.dropbox.com/u/**60102282/Lightning%**20Isokeraunic%20map.JPGhttp://dl.dropbox.com/u/60102282/Lightning%20Isokeraunic%20map.JPG
I have a number of VHF and UHF antennas mounted on my
workshop building but when not in use, they are kept
disconnected where they enter the building.
I have thought about finding some way to bring the GPS
RF signal into my workshop via an optical fiber interface
and sacrifice the RF to optical fiber interface if lightning
strikes it in a treetop but have not found a way to implement
this idea.
Two years ago lightning struck a neighbor's TV antenna
mounted on a pole attached to the side of his house and
started a fire in one of their 2nd floor bedrooms which
did a lot of damage before it was put out. The tower
was well grounded and the coax leading into the room
was fed through a grounded lightning protector but none
of these precautions prevented the fire from the lightning
strike.
Any list folks have ideas on this?
Mike Baker WA4HFR
Gainesville/Micanopy, Fla
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and follow the instructions there.
It seems to me (and I would be more than happy to hear any differing
opinions) that your GPS antenna only needs to be high enough to be able
to see a reasonable slice of sky. i.e. if your workshop were in the
middle of a circular clearing 80 feet in diameter in a forest with an 80
foot tree canopy, 40 feet of elevation gives you a 90 degree slice of
sky. It makes no sense (again, to me) to elevate your antenna in order
to make your choke ring antenna effective against horizontal multipath.
Below the canopy there would be no horizontal multipath to deal with.
Consider your forest as a 'poor mans choke ring antenna upgrade'
As far as fiber isolation of the GPS RF, I have seen many commercial
installations like that, and judging by the cost and complexity of the
equipment used, I would say that solution is pretty non-trivial. Fiber
isolation of the thunderbolt reference clock output and serial control
would be far easier. You might even be able to rig up rudimentary solar
power for the remote portion of the system. That would effectively
eliminate any ground path for lightning.
My 2 cents
Dale Robertson
NV8U
On 4/11/2012 8:50 AM, Michael Baker wrote:
Time-Nutters--
My workshop is surrounded by tall trees (70 to 80 ft). There
is no easy way to place my T-Bolt antenna above the tree-top
foliage. Since choke-ring antennas do not provide much benefit
for dealing with multi-path that originates from directly above
the antenna I have considered putting the antenna on a 10-ft
pole and mounting the pole in the top of the nearby trees so
as to have the antenna just above the tree-top foliage.
However, here in north-central Florida lightning is a serious
problem. In the 12 years we have lived here, 3 trees have
been hit within 75 meters of my workshop building behind
my house.
Here is a DropBox link to a map of lightning-strike-days
in USA locations:
http://dl.dropbox.com/u/60102282/Lightning%20Isokeraunic%20map.JPG
I have a number of VHF and UHF antennas mounted on my
workshop building but when not in use, they are kept
disconnected where they enter the building.
I have thought about finding some way to bring the GPS
RF signal into my workshop via an optical fiber interface
and sacrifice the RF to optical fiber interface if lightning
strikes it in a treetop but have not found a way to implement
this idea.
Two years ago lightning struck a neighbor's TV antenna
mounted on a pole attached to the side of his house and
started a fire in one of their 2nd floor bedrooms which
did a lot of damage before it was put out. The tower
was well grounded and the coax leading into the room
was fed through a grounded lightning protector but none
of these precautions prevented the fire from the lightning
strike.
Any list folks have ideas on this?
Mike Baker WA4HFR
Gainesville/Micanopy, Fla
time-nuts mailing list -- time-nuts@febo.com
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
The simple / stupid approach to the feed lines:
Put up the tower away from all structures
Put the antennas up on the tower.
Ground the tower well.
Run the feed lines down the tower
Ground the feeds both at the antenna and at the base of the tower
Put in a good arrestor at the base of the tower
Run the feed lines underground to where ever you are going to need them
Put in a separate ground at the outside wall of the destination
Bond all the lines to that ground
Protect the lines again with good arrestors
Run them off to where ever you need to use them
Plan on checking / replacing the removable cartridges in the arrestors a few
times a year.
Yes that's a lot. Fires are no fun.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Michael Baker
Sent: Wednesday, April 11, 2012 8:50 AM
To: time-nuts@febo.com
Subject: [time-nuts] Best location for a GPS antenna...?
Time-Nutters--
My workshop is surrounded by tall trees (70 to 80 ft). There
is no easy way to place my T-Bolt antenna above the tree-top
foliage. Since choke-ring antennas do not provide much benefit
for dealing with multi-path that originates from directly above
the antenna I have considered putting the antenna on a 10-ft
pole and mounting the pole in the top of the nearby trees so
as to have the antenna just above the tree-top foliage.
However, here in north-central Florida lightning is a serious
problem. In the 12 years we have lived here, 3 trees have
been hit within 75 meters of my workshop building behind
my house.
Here is a DropBox link to a map of lightning-strike-days
in USA locations:
http://dl.dropbox.com/u/60102282/Lightning%20Isokeraunic%20map.JPG
I have a number of VHF and UHF antennas mounted on my
workshop building but when not in use, they are kept
disconnected where they enter the building.
I have thought about finding some way to bring the GPS
RF signal into my workshop via an optical fiber interface
and sacrifice the RF to optical fiber interface if lightning
strikes it in a treetop but have not found a way to implement
this idea.
Two years ago lightning struck a neighbor's TV antenna
mounted on a pole attached to the side of his house and
started a fire in one of their 2nd floor bedrooms which
did a lot of damage before it was put out. The tower
was well grounded and the coax leading into the room
was fed through a grounded lightning protector but none
of these precautions prevented the fire from the lightning
strike.
Any list folks have ideas on this?
Mike Baker WA4HFR
Gainesville/Micanopy, Fla
time-nuts mailing list -- time-nuts@febo.com
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On Wed, Apr 11, 2012 at 5:50 AM, Michael Baker mpb45@clanbaker.org wrote:
I have thought about finding some way to bring the GPS
RF signal into my workshop via an optical fiber interface
and sacrifice the RF to optical fiber interface if lightning
strikes it in a treetop but have not found a way to implement
this idea.
I always preface my antenna comments with "unless you live in
Florida..." I think the way to use fiber is to place the t-bolt
inside a weathertight box mounted to the antenna mast and then run the
PPS, 10MHz and re-232 out on fiber cables.
Also you don't really need to have the GPS above the trees. Maybe you
can find a compromise locations such that the GPS is NOT the tallest
target in the area.
I was looking to use fiber for something like this too. I found the
best parts to use were those designed for consumer audio s/pdif like
you might have on a home theater recover or flat screen TV. The jacks
are wired up directly to logic level and you can buy the fiber cable
at Best Buy (or cheaper at monoprice.com)
Chris Albertson
Redondo Beach, California
On Wed, Apr 11, 2012 at 7:19 AM, Bob Bownes bownes@gmail.com wrote:
The issue is that this treats the t'bolt as a sacrificial item. I would
contend that, at a cost of $80-90, you could spend far more time and effort
trying to isolate, amplify, correct, and bias the antenna than that is
worth. Effort and gear that would need to be replaced every time
I thought of that right after I suggested using fiber data lines.
You'd loose a few expensive t-bolts. But I think there is a better
and cheaper way to go: Buy a cheap Motorola Oncore receiver. The
Oncore UT costs all of about $18 on eBay, buy four of them. The
only signal you need to bring into the workroom from an Oncore is PPS
and that is "way easy" to do using fiber. The other signals (rs232)
can be connected as needed and that is not often. Then you build a
"standard" GSPDO in the workshop. The initial cost is lower and the
engineering is simple (because only the PPS has to go over fiber)
The Oncore and GPSDO can give as good of result as the t-bolt. It
mostly depends on how good the OCXO is, maybe even you build two
GPSDOs running off the same PPS the second one being Rubinium based.
My $35 Rb can holdover for many weeks (at the level I need) if GPS is
down.
Then you can install the t-bolt with an antenna you can disconnect and
only use the t-bolt now and then during good wearer to double check
the GPSDO that you can leave running 24x7
Chris Albertson
Redondo Beach, California
Don't forget to tighten the fiber connectors and correct for the length of
the fiber or you'll be off by 60ns! ;)
On Wed, Apr 11, 2012 at 1:17 PM, Chris Albertson
albertson.chris@gmail.comwrote:
On Wed, Apr 11, 2012 at 7:19 AM, Bob Bownes bownes@gmail.com wrote:
The issue is that this treats the t'bolt as a sacrificial item. I would
contend that, at a cost of $80-90, you could spend far more time and
effort
trying to isolate, amplify, correct, and bias the antenna than that is
worth. Effort and gear that would need to be replaced every time
I thought of that right after I suggested using fiber data lines.
You'd loose a few expensive t-bolts. But I think there is a better
and cheaper way to go: Buy a cheap Motorola Oncore receiver. The
Oncore UT costs all of about $18 on eBay, buy four of them. The
only signal you need to bring into the workroom from an Oncore is PPS
and that is "way easy" to do using fiber. The other signals (rs232)
can be connected as needed and that is not often. Then you build a
"standard" GSPDO in the workshop. The initial cost is lower and the
engineering is simple (because only the PPS has to go over fiber)
The Oncore and GPSDO can give as good of result as the t-bolt. It
mostly depends on how good the OCXO is, maybe even you build two
GPSDOs running off the same PPS the second one being Rubinium based.
My $35 Rb can holdover for many weeks (at the level I need) if GPS is
down.
Then you can install the t-bolt with an antenna you can disconnect and
only use the t-bolt now and then during good wearer to double check
the GPSDO that you can leave running 24x7
Chris Albertson
Redondo Beach, California
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On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate it?
I mean, rx external antenna -> preamp -> tx directional internal antenna -> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Best regards,
Andrea Baldoni
I suspect that would make the multipath problem even worse.
On Wed, Apr 11, 2012 at 4:06 PM, Andrea Baldoni erm1eaae7@ermione.comwrote:
On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the
t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate
it?
I mean, rx external antenna -> preamp -> tx directional internal antenna
-> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Best regards,
Andrea Baldoni
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
On Wed, 11 Apr 2012 22:06:06 +0200
"Andrea Baldoni" erm1eaae7@ermione.com wrote:
On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate it?
I mean, rx external antenna -> preamp -> tx directional internal antenna -> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Yes it would be. What you basically would need is to have a LNA,
a bandpass filter and something that converts the voltage into
light with very little noise. I think it would be easiest to down
mix it first to 100MHz or so, then modulate a laser diode. In the
house you'd have to mix it up to 1.5GHz again, of course.
I have no clue whether that is feasible from the noise this whole
circuitry will add or whether it would add so much noise that the
receiver would have no chance...
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
On Wed, 11 Apr 2012 22:06:06 +0200
"Andrea Baldoni" erm1eaae7@ermione.com wrote:
I mean, rx external antenna -> preamp -> tx directional internal antenna -> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Oh.. err.. sorry... i read that you would be modulating it onto a fiber
instead... Must be already half asleep ^^'
Yes, it would be possible. But you are not allowed to do it, because
you will be very strong GPS jammer. And don't count on the directivity
of antennas. They are not as directional as people think and the side
and back lobes will jam any receiver nearby
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
Hi
Putting the GPS on a fiber is fine, except you need a very large battery to
keep it running. As soon as you have a power line up to it, you are right
back to a metal conductor going to the wrong place(s).
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Attila Kinali
Sent: Wednesday, April 11, 2012 4:37 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On Wed, 11 Apr 2012 22:06:06 +0200
"Andrea Baldoni" erm1eaae7@ermione.com wrote:
On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the
t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate
it?
I mean, rx external antenna -> preamp -> tx directional internal antenna
-> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Yes it would be. What you basically would need is to have a LNA,
a bandpass filter and something that converts the voltage into
light with very little noise. I think it would be easiest to down
mix it first to 100MHz or so, then modulate a laser diode. In the
house you'd have to mix it up to 1.5GHz again, of course.
I have no clue whether that is feasible from the noise this whole
circuitry will add or whether it would add so much noise that the
receiver would have no chance...
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
time-nuts mailing list -- time-nuts@febo.com
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On Wed, 11 Apr 2012 17:09:32 -0400
"Bob Camp" lists@rtty.us wrote:
Putting the GPS on a fiber is fine, except you need a very large battery to
keep it running. As soon as you have a power line up to it, you are right
back to a metal conductor going to the wrong place(s).
You are at the top list of things to hit for a lightning anyways.
No matter whether you have a ground connection or not. Just simply
because the antenna is up there.
Ie the antenna and everything connected to it is to be sacrificed in an
lightning strike. The question is, how much you have to replace and what
additional damage it can cause.
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
This is a great discussion. I have been trying to decide the best compromise between optimal reception and safety. Here in Boulder afternoon thunder stormers are often a daily occurrence.
I cannot afford to learn from my mistakes on this one.
Thomas Knox
Date: Wed, 11 Apr 2012 22:37:06 +0200
From: attila@kinali.ch
To: time-nuts@febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On Wed, 11 Apr 2012 22:06:06 +0200
"Andrea Baldoni" erm1eaae7@ermione.com wrote:
On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate it?
I mean, rx external antenna -> preamp -> tx directional internal antenna -> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Yes it would be. What you basically would need is to have a LNA,
a bandpass filter and something that converts the voltage into
light with very little noise. I think it would be easiest to down
mix it first to 100MHz or so, then modulate a laser diode. In the
house you'd have to mix it up to 1.5GHz again, of course.
I have no clue whether that is feasible from the noise this whole
circuitry will add or whether it would add so much noise that the
receiver would have no chance...
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
If the antenna is no higher than your house, it's no more likely to get hit than the house. If it's higher than the house by a few feet, the increase in hit probability is vanishingly small. Provided the antenna is grounded as well as your house power (as in very poorly) it's no more a hazard than any other conductor in your home. Run it down to ground level and through a proper protector and it's less of a hazard than the rest of the conductors in the house.
Food for thought: do you have metal downspouts on the gutters? A metal lining in the chimney? Metal heating ducts ? Any bets on how they are grounded...
Bob
On Apr 11, 2012, at 5:34 PM, Tom Knox wrote:
This is a great discussion. I have been trying to decide the best compromise between optimal reception and safety. Here in Boulder afternoon thunder stormers are often a daily occurrence.
I cannot afford to learn from my mistakes on this one.
Thomas Knox
Date: Wed, 11 Apr 2012 22:37:06 +0200
From: attila@kinali.ch
To: time-nuts@febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On Wed, 11 Apr 2012 22:06:06 +0200
"Andrea Baldoni" erm1eaae7@ermione.com wrote:
On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the t'bolt
and the antenna, but to put the isolation between the t'bolt and the
distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate it?
I mean, rx external antenna -> preamp -> tx directional internal antenna -> big
air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe
it could be powered via a magnetic link (or a little solar panel with a
lamp illuminating it).
Yes it would be. What you basically would need is to have a LNA,
a bandpass filter and something that converts the voltage into
light with very little noise. I think it would be easiest to down
mix it first to 100MHz or so, then modulate a laser diode. In the
house you'd have to mix it up to 1.5GHz again, of course.
I have no clue whether that is feasible from the noise this whole
circuitry will add or whether it would add so much noise that the
receiver would have no chance...
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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and follow the instructions there.
There are commercial "re-radiators" for GPS. I found these on Google:
http://www.gps-repeating.com/?gclid=COTV88D6rq8CFcwTfAodhSKvmQ
http://gpsnetworking.com/GPS-re-radiating-kits.asp
One of my old suppliers in the UK was marketing a range of these, but I seem
to remember some problem in getting approval in the UK, and they had to drop
them. Things may have changed as this was a few years ago.
Rob Kimberley
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Andrea Baldoni
Sent: 11 April 2012 21:06
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
I do like the optical isolation suggestion. While less than optimal,
perhaps the easiest solution is not to put the isolation between the
t'bolt and the antenna, but to put the isolation between the t'bolt
and the distribution amplifier.
By the way, would it be possible to retransmit the GPS signal to isolate it?
I mean, rx external antenna -> preamp -> tx directional internal antenna ->
big air gap -> rx directional internal antenna -> receiver.
The preamp would not be so power hungry as the full thunderbolt and maybe it
could be powered via a magnetic link (or a little solar panel with a lamp
illuminating it).
Best regards,
Andrea Baldoni
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 4/12/12 2:09 AM, Rob Kimberley wrote:
There are commercial "re-radiators" for GPS. I found these on Google:
http://www.gps-repeating.com/?gclid=COTV88D6rq8CFcwTfAodhSKvmQ
http://gpsnetworking.com/GPS-re-radiating-kits.asp
One of my old suppliers in the UK was marketing a range of these, but I seem
to remember some problem in getting approval in the UK, and they had to drop
them. Things may have changed as this was a few years ago.
Interestingly I've just been looking into this... Why would you need
anything special to reradiate.. It's not like you need a particular
antenna pattern or constant gain or something. What about something like
a fat monopole against a ground plane, with a attenuator at the feed to
provide a good terminating impedance for the LNA/Line driver.
If it's L1 only, you don't even need particularly wide bandwidth (<1%)
Yes, I've seen setups at JPL where they reradiate with D&M or Ashtech
chokering antennas (or even helibowls), but that might be because we've
got a bunch of them sitting around, so why not use it.
You must read:
http://transition.fcc.gov/eb/Orders/2005/DA-05-2998A1.html
Which discusses a FCC complaint with Navtech for selling GPS receivers.
An exert is presented below:
``Please note: re-radiation kits are currently only
available for purchase to International Customers and in
cases where the U.S. Government is the end user.''
Pursuant to Section 15.201(b) of the Rules, 47 C.F.R. §
15.201(b), intentional radiators must be authorized in accordance
with the FCC's certification procedures prior to the initiation
of marketing in the United States. However, GPS re-radiators
operate within the restricted frequency bands listed in Section
15.205(a) of the Rules, 47 C.F.R. § 15.205(a).4 Thus, GPS re-
radiators cannot comply with the FCC's technical standards and
therefore cannot be certificated or marketed for use by the
general public or non-federal government entities. Accordingly,
it appears that Navtech has violated Section 302(b) of the Act
and Sections 2.803 and 15.205(a) of the Rules by marketing in the
United States radio frequency devices that are not eligible to
receive a grant of certification.
You should be aware that the Commission has recently
addressed a Petition for Rulemaking and a Request for Waiver
seeking amendment of FCC regulations to permit the marketing of
GPS re-radiation kits.5 By Order released July 6, 2005, the
FCC's Office of Engineering and Technology (OET) denied the
Petition for Rulemaking and Request for Waiver.6 OET noted that
the Petition raised significant issues that needed further study
and therefore did not warrant consideration at the time.
Accordingly, Navtech is reminded that at this time GPS re-
radiating devices are not permitted to be sold to the general
public or to state or local governments.
John WA4WDL
From: "Jim Lux" jimlux@earthlink.net
Sent: Thursday, April 12, 2012 9:51 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On 4/12/12 2:09 AM, Rob Kimberley wrote:
There are commercial "re-radiators" for GPS. I found these on Google:
http://www.gps-repeating.com/?gclid=COTV88D6rq8CFcwTfAodhSKvmQ
http://gpsnetworking.com/GPS-re-radiating-kits.asp
One of my old suppliers in the UK was marketing a range of these, but I
seem
to remember some problem in getting approval in the UK, and they had to
drop
them. Things may have changed as this was a few years ago.
I meant to type GPS repeaters not GPS receivers
John WA4WDL
From: "jmfranke" jmfranke@cox.net
Sent: Thursday, April 12, 2012 12:28 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?
You must read:
http://transition.fcc.gov/eb/Orders/2005/DA-05-2998A1.html
Which discusses a FCC complaint with Navtech for selling GPS receivers.
An exert is presented below:
``Please note: re-radiation kits are currently only
available for purchase to International Customers and in
cases where the U.S. Government is the end user.''
Pursuant to Section 15.201(b) of the Rules, 47 C.F.R. §
15.201(b), intentional radiators must be authorized in accordance
with the FCC's certification procedures prior to the initiation
of marketing in the United States. However, GPS re-radiators
operate within the restricted frequency bands listed in Section
15.205(a) of the Rules, 47 C.F.R. § 15.205(a).4 Thus, GPS re-
radiators cannot comply with the FCC's technical standards and
therefore cannot be certificated or marketed for use by the
general public or non-federal government entities. Accordingly,
it appears that Navtech has violated Section 302(b) of the Act
and Sections 2.803 and 15.205(a) of the Rules by marketing in the
United States radio frequency devices that are not eligible to
receive a grant of certification.
You should be aware that the Commission has recently
addressed a Petition for Rulemaking and a Request for Waiver
seeking amendment of FCC regulations to permit the marketing of
GPS re-radiation kits.5 By Order released July 6, 2005, the
FCC's Office of Engineering and Technology (OET) denied the
Petition for Rulemaking and Request for Waiver.6 OET noted that
the Petition raised significant issues that needed further study
and therefore did not warrant consideration at the time.
Accordingly, Navtech is reminded that at this time GPS re-
radiating devices are not permitted to be sold to the general
public or to state or local governments.
John WA4WDL
From: "Jim Lux" jimlux@earthlink.net
Sent: Thursday, April 12, 2012 9:51 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On 4/12/12 2:09 AM, Rob Kimberley wrote:
There are commercial "re-radiators" for GPS. I found these on Google:
http://www.gps-repeating.com/?gclid=COTV88D6rq8CFcwTfAodhSKvmQ
http://gpsnetworking.com/GPS-re-radiating-kits.asp
One of my old suppliers in the UK was marketing a range of these, but I
seem
to remember some problem in getting approval in the UK, and they had to
drop
them. Things may have changed as this was a few years ago.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Rerad-systems are getting controlled in Europe too.
http://www.etsi.org/deliver/etsi_en/302600_302699/302645/01.01.01_60/en_302645v010101p.pdf
Any reports on how quick this is going? Where I live, there are rules, but
not many are aware of them.
Björn
You must read:
http://transition.fcc.gov/eb/Orders/2005/DA-05-2998A1.html
Which discusses a FCC complaint with Navtech for selling GPS reradiating
kits.
An exert is presented below:
``Please note: re-radiation kits are currently only
available for purchase to International Customers and in
cases where the U.S. Government is the end user.''
Hi
GPS is pretty close to the noise "as received". A fully passive system with
significant cable loss and low / no gain antennas does not sound like it's
going to do a very good job.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Jim Lux
Sent: Thursday, April 12, 2012 9:52 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On 4/12/12 2:09 AM, Rob Kimberley wrote:
There are commercial "re-radiators" for GPS. I found these on Google:
http://www.gps-repeating.com/?gclid=COTV88D6rq8CFcwTfAodhSKvmQ
http://gpsnetworking.com/GPS-re-radiating-kits.asp
One of my old suppliers in the UK was marketing a range of these, but I
seem
to remember some problem in getting approval in the UK, and they had to
drop
them. Things may have changed as this was a few years ago.
Interestingly I've just been looking into this... Why would you need
anything special to reradiate.. It's not like you need a particular
antenna pattern or constant gain or something. What about something like
a fat monopole against a ground plane, with a attenuator at the feed to
provide a good terminating impedance for the LNA/Line driver.
If it's L1 only, you don't even need particularly wide bandwidth (<1%)
Yes, I've seen setups at JPL where they reradiate with D&M or Ashtech
chokering antennas (or even helibowls), but that might be because we've
got a bunch of them sitting around, so why not use it.
time-nuts mailing list -- time-nuts@febo.com
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On Wed, Apr 11, 2012 at 3:08 PM, Bob Camp lists@rtty.us wrote:
Hi
If the antenna is no higher than your house, it's no more likely to get hit than the house.
If it's higher than the house by a few feet, the increase in hit probability is vanishingly small.
Antenna do not have to be directly hit to destroy the receiver. Let's
say that something 100 feet away is hit. The nearby strike is
thousands of amps of current in a brief pulse. What you have is
a strong electromagnetic field pulse. This will induce current in any
nearby conductor, including your antenna mast, power lines, phone
lines and even the copper traces on a PCB. The effects vary based on
the geometry. One does not even worry about a direct hit. It is
rare and if it happens your equipment is vaporized. But near hits
happen all the time you can expect them and they are mostly the cause
of damaged equipment and it is actually posable to protect against a
nearby hit.
Think of lightening like a 1,000 pound bomb. If one falls from the
sky on a city and hits you on the head you are dead. But most of the
people effected by the bomb did NOT get hit on the head and were
varying distances from it and for most of them various protection
measures can be very effective.
Redondo Beach, California
On Thu, 12 Apr 2012 12:41:51 -0400
"Bob Camp" lists@rtty.us wrote:
GPS is pretty close to the noise "as received". A fully passive system with
significant cable loss and low / no gain antennas does not sound like it's
going to do a very good job.
GPS is pretty much under the noise "as received" :-)
At least in urban regions with lots of noise around, the GPS signal is
burried deep within the noise. In rural areas the signal of a single
satelite is still below thermal noise. The combined signal of all satelites
can be above noise though.
Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
Hi
Some of the people posting to the thread seem to be concerned about the
house burning down because they put up a GPS antenna...
Receivers can die from a lot of causes. A TBolt like GPS being killed by
input overload from a strike 100 feet away would not be very high on my list
of likely problems.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chris Albertson
Sent: Thursday, April 12, 2012 12:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best location for a GPS antenna...?
On Wed, Apr 11, 2012 at 3:08 PM, Bob Camp lists@rtty.us wrote:
Hi
If the antenna is no higher than your house, it's no more likely to get
hit than the house.
If it's higher than the house by a few feet, the increase in hit
probability is vanishingly small.
Antenna do not have to be directly hit to destroy the receiver. Let's
say that something 100 feet away is hit. The nearby strike is
thousands of amps of current in a brief pulse. What you have is
a strong electromagnetic field pulse. This will induce current in any
nearby conductor, including your antenna mast, power lines, phone
lines and even the copper traces on a PCB. The effects vary based on
the geometry. One does not even worry about a direct hit. It is
rare and if it happens your equipment is vaporized. But near hits
happen all the time you can expect them and they are mostly the cause
of damaged equipment and it is actually posable to protect against a
nearby hit.
Think of lightening like a 1,000 pound bomb. If one falls from the
sky on a city and hits you on the head you are dead. But most of the
people effected by the bomb did NOT get hit on the head and were
varying distances from it and for most of them various protection
measures can be very effective.
Redondo Beach, California
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On Thu, 12 Apr 2012 18:41:43 +0200
bg@lysator.liu.se wrote:
Rerad-systems are getting controlled in Europe too.
http://www.etsi.org/deliver/etsi_en/302600_302699/302645/01.01.01_60/en_302645v010101p.pdf
Any reports on how quick this is going? Where I live, there are rules, but
not many are aware of them.
Interesting, I thought that repeaters were covered by the standard
frequency regulation: ie they are forbidden (or in long: you are not
allowed to make radiations in a frequency band you are not licensed to
send). Unless of course, these repeaters do not fall under the
"radio devices" category, which then the radiation would be simply EMI :-)
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
Michael,
There is a very effective fix: move!
:)
I live in NW Florida and I believe I have found a good solution to the lightning problem.
Since lightning never strikes the same place twice (or so goes conventional wisdom), I built my 60' antenna tower a few feet from the exact spot where a tree had been destroyed by lightning 5 years prior. That was 20 years ago, so far, so good...
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: Michael Baker mpb45@clanbaker.org
Sender: time-nuts-bounces@febo.com
Date: Wed, 11 Apr 2012 08:50:24
To: time-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Best location for a GPS antenna...?
Time-Nutters--
My workshop is surrounded by tall trees (70 to 80 ft). There
is no easy way to place my T-Bolt antenna above the tree-top
foliage. Since choke-ring antennas do not provide much benefit
for dealing with multi-path that originates from directly above
the antenna I have considered putting the antenna on a 10-ft
pole and mounting the pole in the top of the nearby trees so
as to have the antenna just above the tree-top foliage.
However, here in north-central Florida lightning is a serious
problem. In the 12 years we have lived here, 3 trees have
been hit within 75 meters of my workshop building behind
my house.
Here is a DropBox link to a map of lightning-strike-days
in USA locations:
http://dl.dropbox.com/u/60102282/Lightning%20Isokeraunic%20map.JPG
I have a number of VHF and UHF antennas mounted on my
workshop building but when not in use, they are kept
disconnected where they enter the building.
I have thought about finding some way to bring the GPS
RF signal into my workshop via an optical fiber interface
and sacrifice the RF to optical fiber interface if lightning
strikes it in a treetop but have not found a way to implement
this idea.
Two years ago lightning struck a neighbor's TV antenna
mounted on a pole attached to the side of his house and
started a fire in one of their 2nd floor bedrooms which
did a lot of damage before it was put out. The tower
was well grounded and the coax leading into the room
was fed through a grounded lightning protector but none
of these precautions prevented the fire from the lightning
strike.
Any list folks have ideas on this?
Mike Baker WA4HFR
Gainesville/Micanopy, Fla
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Not good Didier!
Rob K
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of shalimr9@gmail.com
Sent: 13 April 2012 17:32
To: Time-Nuts
Subject: Re: [time-nuts] Best location for a GPS antenna...?
Michael,
There is a very effective fix: move!
:)
I live in NW Florida and I believe I have found a good solution to the
lightning problem.
Since lightning never strikes the same place twice (or so goes conventional
wisdom), I built my 60' antenna tower a few feet from the exact spot where a
tree had been destroyed by lightning 5 years prior. That was 20 years ago,
so far, so good...
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: Michael Baker mpb45@clanbaker.org
Sender: time-nuts-bounces@febo.com
Date: Wed, 11 Apr 2012 08:50:24
To: time-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Best location for a GPS antenna...?
Time-Nutters--
My workshop is surrounded by tall trees (70 to 80 ft). There is no easy way
to place my T-Bolt antenna above the tree-top
foliage. Since choke-ring antennas do not provide much benefit
for dealing with multi-path that originates from directly above the antenna
I have considered putting the antenna on a 10-ft pole and mounting the pole
in the top of the nearby trees so as to have the antenna just above the
tree-top foliage.
However, here in north-central Florida lightning is a serious
problem. In the 12 years we have lived here, 3 trees have
been hit within 75 meters of my workshop building behind my house.
Here is a DropBox link to a map of lightning-strike-days in USA locations:
http://dl.dropbox.com/u/60102282/Lightning%20Isokeraunic%20map.JPG
I have a number of VHF and UHF antennas mounted on my workshop building but
when not in use, they are kept disconnected where they enter the building.
I have thought about finding some way to bring the GPS RF signal into my
workshop via an optical fiber interface and sacrifice the RF to optical
fiber interface if lightning strikes it in a treetop but have not found a
way to implement this idea.
Two years ago lightning struck a neighbor's TV antenna mounted on a pole
attached to the side of his house and started a fire in one of their 2nd
floor bedrooms which did a lot of damage before it was put out. The tower
was well grounded and the coax leading into the room was fed through a
grounded lightning protector but none of these precautions prevented the
fire from the lightning strike.
Any list folks have ideas on this?
Mike Baker WA4HFR
Gainesville/Micanopy, Fla
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.