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kboatright1(at)comcast.ne
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 Posted: Sun Aug 12, 2007 10:25 am Post subject: GPS/XM antenna interference |
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No input regarding XM devices vs GPS, but I've learned to put some distance between my MP3 player and my GPS antenna.
KB
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dcw(at)mnwing.org
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| Posted: Mon Aug 13, 2007 4:46 am Post subject: GPS/XM antenna interference |
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On 8/12/07 1:05 PM, "Fiveonepw(at)aol.com" <Fiveonepw(at)aol.com> wrote:
| Quote: | At an OSH forum it was recommended to not locate active antennas(ae?) next to each other as their active electronics could degrade or corrupt data from them. I've been unable to find any such restrictions in the installation information provided with the equipment which includes GNS430W, GRT Dual Horizons with XM satellite and internal GPS, Trutrak ADI with it's own GPS, for a total of 3 GPS antennas(ae?) and one XM receiver. I'd like to mount these on a common shelf at the top of the firewall under the cowl.
Each antenna appears to have a simple coaxial connection which tells me little of it's "active" capability or if these are simple (non-active) devices, although I know the antenna for the 430W is a dedicated unit (not same as non-W unit). The antenna for the ADI is a Laipac Tech model GLP1.
Before I contact the various suppliers tomorrow, does anyone have any actual experience with this or know of any installation requirements/recommended practices for these devices, or is this more Urban Legend?
Mark Phillips
(with apologies for posting to multiple lists!)
Mark:
I have my normal GPS antenna mounted immediately adjacent to my XM WX antenna (for my Anywhere Map system). There seems to be no issues what so ever. I would not place them near a transmitting antenna however.
Doug Weiler
RV-4, 400 hrs
AOL.com.
il Forum -
>http://www.matronics.com/Navigator?RV-List
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vpalermo(at)tampabay.rr.c
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| Posted: Mon Aug 13, 2007 2:25 pm Post subject: GPS/XM antenna interference |
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MarkThe antennas will not interact with each other but should be at least 24 inches from other types of active antennas(comm). If you want to see if it is an active antenna, take the tnc off, turn on the gns 430w/530w and measure from the center conductor to the shield with a voltmeter and you will find that there is 5 vdc at that point.
Vincent Palermo
On Aug 13, 2007, at 8:26 AM, Doug Weiler wrote:
[quote]
On 8/12/07 1:05 PM, "Fiveonepw(at)aol.com (Fiveonepw(at)aol.com)" <Fiveonepw(at)aol.com (Fiveonepw(at)aol.com)> wrote:
| Quote: | At an OSH forum it was recommended to not locate active antennas(ae?) next to each other as their active electronics could degrade or corrupt data from them. I've been unable to find any such restrictions in the installation information provided with the equipment which includes GNS430W, GRT Dual Horizons with XM satellite and internal GPS, Trutrak ADI with it's own GPS, for a total of 3 GPS antennas(ae?) and one XM receiver. I'd like to mount these on a common shelf at the top of the firewall under the cowl.
Each antenna appears to have a simple coaxial connection which tells me little of it's "active" capability or if these are simple (non-active) devices, although I know the antenna for the 430W is a dedicated unit (not same as non-W unit). The antenna for the ADI is a Laipac Tech model GLP1.
Before I contact the various suppliers tomorrow, does anyone have any actual experience with this or know of any installation requirements/recommended practices for these devices, or is this more Urban Legend?
Mark Phillips
(with apologies for posting to multiple lists!)
Mark:
I have my normal GPS antenna mounted immediately adjacent to my XM WX antenna (for my Anywhere Map system). There seems to be no issues what so ever. I would not place them near a transmitting antenna however.
Doug Weiler
RV-4, 400 hrs
AOL.com.
il Forum -
>http://www.matronics.com/Navigator?RV-List
; - NEW MATRONICS WEB FORUMS -
matronics.com
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href="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List
href="http://forums.matronics.com">http://forums.matronics.com
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Larry Bowen
Joined: 09 Jan 2006
Posts: 802
Location: NC, USA
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| Posted: Mon Aug 13, 2007 5:27 pm Post subject: GPS/XM antenna interference |
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I have 3 ants as close as possible to each other on the RV-8 glareshield and haven't noticed any ill effects. (396 GPS & XM Weather & XM radio)
--
Larry Bowen
Larry(at)BowenAero.com (Larry(at)BowenAero.com)
http://BowenAero.com
On 8/13/07, Vincent Palermo <vpalermo(at)tampabay.rr.com (vpalermo(at)tampabay.rr.com)> wrote:[quote] MarkThe antennas will not interact with each other but should be at least 24 inches from other types of active antennas(comm). If you want to see if it is an active antenna, take the tnc off, turn on the gns 430w/530w and measure from the center conductor to the shield with a voltmeter and you will find that there is 5 vdc at that point.
Vincent Palermo
On Aug 13, 2007, at 8:26 AM, Doug Weiler wrote:
[quote]
On 8/12/07 1:05 PM, "Fiveonepw(at)aol.com" < Fiveonepw(at)aol.com> wrote:
| Quote: | At an OSH forum it was recommended to not locate active antennas(ae?) next to each other as their active electronics could degrade or corrupt data from them. I've been unable to find any such restrictions in the installation information provided with the equipment which includes GNS430W, GRT Dual Horizons with XM satellite and internal GPS, Trutrak ADI with it's own GPS, for a total of 3 GPS antennas(ae?) and one XM receiver. I'd like to mount these on a common shelf at the top of the firewall under the cowl.
Each antenna appears to have a simple coaxial connection which tells me little of it's "active" capability or if these are simple (non-active) devices, although I know the antenna for the 430W is a dedicated unit (not same as non-W unit). The antenna for the ADI is a Laipac Tech model GLP1.
Before I contact the various suppliers tomorrow, does anyone have any actual experience with this or know of any installation requirements/recommended practices for these devices, or is this more Urban Legend?
Mark Phillips
(with apologies for posting to multiple lists!)
Mark:
I have my normal GPS antenna mounted immediately adjacent to my XM WX antenna (for my Anywhere Map system). There seems to be no issues what so ever. I would not place them near a transmitting antenna however.
Doug Weiler
RV-4, 400 hrs
AOL.com.
il Forum -
> http://www.matronics.com/Navigator?RV-List
; - NEW MATRONICS WEB FORUMS -
matronics.com
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[b] http://www.matronics.com/Navigator?RV-List http://forums.matronics.com [quote][b]
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Larry Bowen
RV-8 SOLD,
RV-7QB in progress... |
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reichec
Joined: 23 Apr 2007
Posts: 26
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| Posted: Mon Aug 13, 2007 6:16 pm Post subject: GPS/XM antenna interference |
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This is not the test of an "active" antenna, that being really one that tranmits RF, like com antennas, active traffic (tcas, skywatch) and transponder antennas.... also satcom ( as far from every other antenna as possible) 5V at the antenna just means there is a preamp in the antenna. Passive antennas are ones such as ADF loop and sense, GPS, XM radio, Marker Beacon, and stormscope antennas. You can line those GPS and XM antennas right up next to each other no problems!
Charlie
Make sure you have enough cable loss or attenuation with your GNS X30 WAAS system!
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Mark Phillips in TN
Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN
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| Posted: Mon Aug 13, 2007 9:10 pm Post subject: GPS/XM antenna interference |
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In a message dated 8/13/2007 9:22:26 PM Central Daylight Time, reichec(at)verizon.net writes:
| Quote: | | Make sure you have enough cable loss or attenuation with your GNS X30 WAAS system! |
No kidding- I'm trying to figure out some place to loop 7' in one direction and the other 7' opposite to cancel itself out! 
Thanks to all who replied on this (Chris, David, Alan, Doug, Randy, Vincent, Larry, Charlie & anyone I missed!)- will proceed with planned antenna farm...
Mark - do not archive
[quote][b]
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Mark Phillips in TN
Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN
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| Posted: Tue Aug 14, 2007 12:30 pm Post subject: GPS/XM antenna interference |
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Just to pass along my learnings- after contacting the techies at Garmin, Trutrak and GRT, none expressed any concerns or related any experiences where locating these antennas(ae?) next to each other would create any problems. None of the replies from the various lists indicated much of a problem either- at least no one identified any specific technical issues. Proceeding as planned-
From the Antenna Farm...
Mark
(again, apologies for multi-list posting!)
AOL.com.
[quote][b]
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pitts_pilot(at)bellsouth.
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| Posted: Thu Aug 16, 2007 7:30 am Post subject: GPS/XM antenna interference |
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Fiveonepw(at)aol.com (Fiveonepw(at)aol.com) wrote:
| Quote: | Just to pass along my learnings- after contacting the techies at Garmin, Trutrak and GRT, none expressed any concerns or related any experiences where locating these antennas(ae?) next to each other would create any problems.
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That's because 'active', in this case, refers to the fact that there's electrically powered circuits (in this case an amplifier) in the antenna to increase it's signal-to-noise ratio. The GPS antennas, however, can be swamped by being placed too near a transmitting antenna.
| Quote: | None of the replies from the various lists indicated much of a problem either- at least no one identified any specific technical issues.
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Well, that's because there isn't any. Mounting receiver antennas in a close group and transmitting antennas in a close group usually (never say never) will not have any negative impact. Mixing them close together probably will.
Also be aware that some Narco (don't know about others) radios are so poorly shielded that when tuned to some comm freqs will kill the GPS signal. You don't have to transmit ..... just being tuned to the freq will cause the problem.
Linn
do not archive
[quote] Proceeding as planned-
From the Antenna Farm...
Mark
(again, apologies for multi-list posting!)
AOL.com.
[b]
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pitts_pilot(at)bellsouth.
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| Posted: Thu Aug 16, 2007 10:45 am Post subject: GPS/XM antenna interference |
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Charles Reiche wrote:
| Quote: | This is not the test of an "active" antenna, that being really one that tranmits RF, like com antennas, active traffic (tcas, skywatch) and transponder antennas.... also satcom ( as far from every other antenna as possible) 5V at the antenna just means there is a preamp in the antenna.
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Charlie, lemme disagree here. Almost all (never say 'all' or 'never') active antennas are receiver antennas. Such as those with a preamp, like the GPS antennas we're talking about here. Almost all (same caveat here) transmit antennas are passive. There are exceptions to both these categories, but none apply to aviation AFAIK.
| Quote: | Passive antennas are ones such as ADF loop and sense, GPS, XM radio, Marker Beacon, and stormscope antennas.
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True .... good examples of passive receiver antennas.
| Quote: | You can line those GPS and XM antennas right up next to each other no problems!
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And passive receiver antennas too.
Linn
do not archive
[quote]
Charlie
Make sure you have enough cable loss or attenuation with your GNS X30 WAAS system!
| Quote: | ----- Original Message -----
From: Vincent Palermo (vpalermo(at)tampabay.rr.com)
To: rv-list(at)matronics.com (rv-list(at)matronics.com)
Sent: Monday, August 13, 2007 6:24 PM
Subject: Re: GPS/XM antenna interference
Mark The antennas will not interact with each other but should be at least 24 inches from other types of active antennas(comm). If you want to see if it is an active antenna, take the tnc off, turn on the gns 430w/530w and measure from the center conductor to the shield with a voltmeter and you will find that there is 5 vdc at that point.
Vincent Palermo
On Aug 13, 2007, at 8:26 AM, Doug Weiler wrote:
| Quote: |
On 8/12/07 1:05 PM, "Fiveonepw(at)aol.com (Fiveonepw(at)aol.com)" <Fiveonepw(at)aol.com (Fiveonepw(at)aol.com)> wrote:
| Quote: | At an OSH forum it was recommended to not locate active antennas(ae?) next to each other as their active electronics could degrade or corrupt data from them. I've been unable to find any such restrictions in the installation information provided with the equipment which includes GNS430W, GRT Dual Horizons with XM satellite and internal GPS, Trutrak ADI with it's own GPS, for a total of 3 GPS antennas(ae?) and one XM receiver. I'd like to mount these on a common shelf at the top of the firewall under the cowl.
Each antenna appears to have a simple coaxial connection which tells me little of it's "active" capability or if these are simple (non-active) devices, although I know the antenna for the 430W is a dedicated unit (not same as non-W unit). The antenna for the ADI is a Laipac Tech model GLP1.
Before I contact the various suppliers tomorrow, does anyone have any actual experience with this or know of any installation requirements/recommended practices for these devices, or is this more Urban Legend?
Mark Phillips
(with apologies for posting to multiple lists!)
Mark:
I have my normal GPS antenna mounted immediately adjacent to my XM WX antenna (for my Anywhere Map system). There seems to be no issues what so ever. I would not place them near a transmitting antenna however.
Doug Weiler
RV-4, 400 hrs
AOL.com.
il Forum -
>http://www.matronics.com/Navigator?RV-List
; - NEW MATRONICS WEB FORUMS -
matronics.com
|
href="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List
href="http://forums.matronics.com">http://forums.matronics.com
|
|
[b]
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pbesing(at)yahoo.com
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| Posted: Fri Aug 17, 2007 6:31 am Post subject: GPS/XM antenna interference |
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I have a Garmin 396...I have the XM/Sat antenna literally 1/4" from eachother and they have not had a single problem in over 100 hours. And, I had to use and extender cable. They are behind the back seat on the turtledeck of my RV-4.
Paul Besing
linn Walters <pitts_pilot(at)bellsouth.net> wrote:
[quote]Charles Reiche wrote:
| Quote: | This is not the test of an "active" antenna, that being really one that tranmits RF, like com antennas, active traffic (tcas, skywatch) and transponder antennas.... also satcom ( as far from every other antenna as possible) 5V at the antenna just means there is a preamp in the antenna.
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Charlie, lemme disagree here. Almost all (never say 'all' or 'never') active antennas are receiver antennas. Such as those with a preamp, like the GPS antennas we're talking about here. Almost all (same caveat here) transmit antennas are passive. There are exceptions to both these categories, but none apply to aviation AFAIK.
| Quote: | Passive antennas are ones such as ADF loop and sense, GPS, XM radio, Marker Beacon, and stormscope antennas.
|
True .... good examples of passive receiver antennas.
| Quote: | You can line those GPS and XM antennas right up next to each other no problems!
|
And passive receiver antennas too.
Linn
do not archive
[quote]
Charlie
Make sure you have enough cable loss or attenuation with your GNS X30 WAAS system!
[quote] ---
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http://www.matronics.com/Navigator?RV-List |
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pitts_pilot(at)bellsouth.
Guest
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| Posted: Fri Aug 17, 2007 4:55 pm Post subject: GPS/XM antenna interference |
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Doug Weiler wrote:
| Quote: | Re: GPS/XM antenna interference
On 8/12/07 1:05 PM, "Fiveonepw(at)aol.com" (Fiveonepw(at)aol.com) <Fiveonepw(at)aol.com> (Fiveonepw(at)aol.com) wrote:
| Quote: | | At an OSH forum it was recommended to not locate active antennas(ae?) next to each other as their active electronics could degrade or corrupt data from them. I've been unable to find any such restrictions in the installation information provided with the equipment which includes GNS430W, GRT Dual Horizons with XM satellite and internal GPS, Trutrak ADI with it's own GPS, for a total of 3 GPS antennas(ae?) and one XM receiver. I'd like to mount these on a common shelf at the top of the firewall under the cowl. |
|
There that caveat 'could'. Now don't get me wrong .... I'm not an 'expert', but have extensive electronics background. Sleeping in the Holiday Inn Express really didn't help shed any light on this thread. The 'active' part is an amplifier that boosts the meager signal from the satellite. I'm sure it's possible to design an active receiver antenna that radiates enough garbage to impact another active receiver next to it. However, the design just wouldn't get past certification. So I feel confident in saying 'go for it'. | Quote: | | Quote: | | Each antenna appears to have a simple coaxial connection which tells me little of it's "active" capability or if these are simple (non-active) devices, although I know the antenna for the 430W is a dedicated unit (not same as non-W unit). The antenna for the ADI is a Laipac Tech model GLP1. |
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The antennas I'm talking about (satellite receiver types) generally use 5V to power the unit, through the same coax that the signal comes through. I'm not familiar with the ADI antenna.
| Quote: | | Quote: | | Before I contact the various suppliers tomorrow, does anyone have any actual experience with this or know of any installation requirements/recommended practices for these devices, or is this more Urban Legend? |
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No actual experience on my part ..... just applying the thought process to the 'problem'. So, to answer this question, my advice is not to talk to the various suppliers. There opinion will probably be couched in CYA rather than sound electronic principles. They also know nothing (relatively) about the other equipment and haven't a clue if there would be a problem. Now, before y'all get the guns out .... there are some really widely knowledgeable techs and engineers out there .... but finding them is the problem.
| Quote: | | Quote: | Mark Phillips
(with apologies for posting to multiple lists!)
Mark:
I have my normal GPS antenna mounted immediately adjacent to my XM WX antenna (for my Anywhere Map system). There seems to be no issues what so ever. I would not place them near a transmitting antenna however. |
|
Amen!
Linn
do not archive
[quote]
[b]
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Mark Phillips in TN
Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN
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| Posted: Sat Aug 18, 2007 7:36 pm Post subject: GPS/XM antenna interference |
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In a message dated 08/17/2007 7:57:25 PM Central Daylight Time, pitts_pilot(at)bellsouth.net writes:
| Quote: | | There opinion will probably be couched in CYA rather than sound electronic principles. |
Each supplier (Garmin, GRT & Trutrak) refreshingly did no such thing and said they could offer no evidence there would be a problem- neat, huh?
Thanks again to all who chimed in on this "problem". FWIW, the OSH Forum was "Airplane Wiring for Smart People" by BMAs Greg Richter. He claimed that a plane he had worked on had a serious interference problem from these type antennas(ae?) that was solved by locating them apart (18"? can't recall exactly what distance he cited). Very possibly true, but based on responses here and on other lists, I'd suspect the interference came from some influence not related to the antennas(ae?) themselves...
Appreciate the discussion, folks!
Mark
[quote][b]
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From The PossumWorks... |
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reichec
Joined: 23 Apr 2007
Posts: 26
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| Posted: Sun Aug 19, 2007 5:42 am Post subject: GPS/XM antenna interference |
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Just like when you transmit on one of your com transmitters and your GPS goverage gets knocked out... you need a notch filter on something but alot of times its the ELT, pop a gps freq notch filter in there and the problem goes away and has not effect on ELT operation. RF is going down the ELT coax and exciting the transmitter circuit in the ELT and making harmonics all the way up to the GPS freqs. Not necesarily the first place you might look but its a solution.. Sure some solutions to antenna placement includ CYA but sometimes these CYA approaches result differently due to coax runs and spacing, etc.
I dont want to start a flame war but there is alot of noise and heat under the cowl, thats the last place I would want to put an expensive GPS or WX antenna.
Charles
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