I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem? Are there any "configurations" that
might not pose a problem? (i.e. 2 furthest sides only, half of bottom
only, etc).

Thanks in advance for any insight!
Dave

On 30 Jun 2004 13:00:23 -0700, (David Harper)
wrote:

I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem? Are there any "configurations" that
might not pose a problem? (i.e. 2 furthest sides only, half of bottom
only, etc).

I am adding in the sci.geo.satellite-nav newsgroup, as people there
are familiar with GPS antenna issues, and could explain this better
than I can.

First, you need to know what style of antenna your GPS has. Most are
either a patch antenna (the Garmin eTrex series) or a quad helix
antenna (some Garmin and most Magellan). The positioning and shielding
issues are rather different for the two.

You are right to be concerned about reflected signals, or multi-path,
issues. That can degrade accuracy.

Also consider a GPS model with provision for an external antenna,
which might give you more mounting options. You could have a
completely shielded box, with a passthrough for the GPS antenna cable,
to the antenna mounted completely outside the shielding.

Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

On 30 Jun 2004 13:00:23 -0700, (David Harper)
wrote:

I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem? Are there any "configurations" that
might not pose a problem? (i.e. 2 furthest sides only, half of bottom
only, etc).

I am adding in the sci.geo.satellite-nav newsgroup, as people there
are familiar with GPS antenna issues, and could explain this better
than I can.

First, you need to know what style of antenna your GPS has. Most are
either a patch antenna (the Garmin eTrex series) or a quad helix
antenna (some Garmin and most Magellan). The positioning and shielding
issues are rather different for the two.

You are right to be concerned about reflected signals, or multi-path,
issues. That can degrade accuracy.

Also consider a GPS model with provision for an external antenna,
which might give you more mounting options. You could have a
completely shielded box, with a passthrough for the GPS antenna cable,
to the antenna mounted completely outside the shielding.

Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

It is a reflector, and will change the pattern. How much depends on how the
Al is configured to the antenna, and the spacing. The wavelength is about 1
foot, so your dimentions indicate that something will happen. (10 inch or
10 foot?) Quickest way is to just try it. The type of antenna the handheld
has determines quite a bit too. THe antenna needs to see the sky, many times
it dosent matter what it is mounted on, but then you have a handheld, that
can be different.

"David Harper" wrote in message
om...
I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem? Are there any "configurations" that
might not pose a problem? (i.e. 2 furthest sides only, half of bottom
only, etc).

Thanks in advance for any insight!
Dave

It is a reflector, and will change the pattern. How much depends on how the
Al is configured to the antenna, and the spacing. The wavelength is about 1
foot, so your dimentions indicate that something will happen. (10 inch or
10 foot?) Quickest way is to just try it. The type of antenna the handheld
has determines quite a bit too. THe antenna needs to see the sky, many times
it dosent matter what it is mounted on, but then you have a handheld, that
can be different.

"David Harper" wrote in message
om...
I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem? Are there any "configurations" that
might not pose a problem? (i.e. 2 furthest sides only, half of bottom
only, etc).

Thanks in advance for any insight!
Dave

Gary S. wrote:

On 30 Jun 2004 13:00:23 -0700, (David Harper)
wrote:


I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem?

I'd expect this to be alright as long as the GPS antenna still has a
clear view of most of the sky - i.e. if you imagine your eye being at
the location of the antenna, it should be able to directly see most of
the sky without needing to look through any aluminum foil. Multipath
problems from reflections tend to be more of an issue when the direct
path is blocked so the receiver only gets the reflected signal and when
the path length of the reflected signal is substantially different than
it would be for the direct signal. Neither would be the case here.
There could still be some destructive interference from reflected
signals but that problem is minimized if the direct signal path is
unobstructed and therefore the strongest signal and by the selective
antenna gain for signals of the proper circular polarization.

Gary S. wrote:

On 30 Jun 2004 13:00:23 -0700, (David Harper)
wrote:


I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem?

I'd expect this to be alright as long as the GPS antenna still has a
clear view of most of the sky - i.e. if you imagine your eye being at
the location of the antenna, it should be able to directly see most of
the sky without needing to look through any aluminum foil. Multipath
problems from reflections tend to be more of an issue when the direct
path is blocked so the receiver only gets the reflected signal and when
the path length of the reflected signal is substantially different than
it would be for the direct signal. Neither would be the case here.
There could still be some destructive interference from reflected
signals but that problem is minimized if the direct signal path is
unobstructed and therefore the strongest signal and by the selective
antenna gain for signals of the proper circular polarization.

I'm not reading this thing, but maybe it's got something you can use :-)

http://www.geomatics.ucalgary.ca/~cannon/99NTMJR.pdf



--

"Peter" wrote in message
...
Gary S. wrote:

On 30 Jun 2004 13:00:23 -0700, (David Harper)
wrote:


I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem?

I'd expect this to be alright as long as the GPS antenna still has a
clear view of most of the sky - i.e. if you imagine your eye being at
the location of the antenna, it should be able to directly see most of
the sky without needing to look through any aluminum foil. Multipath
problems from reflections tend to be more of an issue when the direct
path is blocked so the receiver only gets the reflected signal and when
the path length of the reflected signal is substantially different than
it would be for the direct signal. Neither would be the case here.
There could still be some destructive interference from reflected
signals but that problem is minimized if the direct signal path is
unobstructed and therefore the strongest signal and by the selective
antenna gain for signals of the proper circular polarization.

I'm not reading this thing, but maybe it's got something you can use :-)

http://www.geomatics.ucalgary.ca/~cannon/99NTMJR.pdf



--

"Peter" wrote in message
...
Gary S. wrote:

On 30 Jun 2004 13:00:23 -0700, (David Harper)
wrote:


I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem?

I'd expect this to be alright as long as the GPS antenna still has a
clear view of most of the sky - i.e. if you imagine your eye being at
the location of the antenna, it should be able to directly see most of
the sky without needing to look through any aluminum foil. Multipath
problems from reflections tend to be more of an issue when the direct
path is blocked so the receiver only gets the reflected signal and when
the path length of the reflected signal is substantially different than
it would be for the direct signal. Neither would be the case here.
There could still be some destructive interference from reflected
signals but that problem is minimized if the direct signal path is
unobstructed and therefore the strongest signal and by the selective
antenna gain for signals of the proper circular polarization.

"Dama Foster" wrote in message ...
It is a reflector, and will change the pattern. How much depends on how the
Al is configured to the antenna, and the spacing. The wavelength is about 1
foot, so your dimentions indicate that something will happen. (10 inch or
10 foot?) Quickest way is to just try it. The type of antenna the handheld
has determines quite a bit too. THe antenna needs to see the sky, many times
it dosent matter what it is mounted on, but then you have a handheld, that
can be different.

"David Harper" wrote in message
om...
I was wondering what effect aluminum foil (used as a radiation heat
shield) would have on GPS signal reception? The scenario is a small
payload container (approx 10" cube) covered in polystyrene, with a
handheld GPS reciever located near the top on one corner.

Would aluminum foil on the inner sides (and/or bottom) interfere with
the reception of the signal? I'm worried about possible reflection or
other mechanisms of interference that might occur and prevent good
reception. Basically, my question is, would foil on the sides or the
bottom pose a reception problem? Are there any "configurations" that
might not pose a problem? (i.e. 2 furthest sides only, half of bottom
only, etc).

Thanks in advance for any insight!
Dave

Thanks for all the help people. Based on the info, I think I'll look
into replacing the handheld (etrex) with an OEM sensor and an external
antenna. Some of the OEM sensors are running under $100.

THanks again!
Dave