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GPS outage in fiberglass plane

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jsbougher(at)yahoo.com
Guest

Posted: Tue Aug 24, 2010 2:56 am Post subject: GPS outage in fiberglass plane

I fly a purchased Velocity.  I'm about 1/3 through Bob's book and generally not good with electrical issues - hence the book.  What I have learned is that there is a lot of knowledge on this board.



I have the following problem.  On the ground, panel mounted Garmin 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes and I lose GPS signal on both almost simultaneously.  Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I get GPS signal back it is intermittent.  When I look at the 396 GPS page, it doesn't show ANY signal on ANY satellite.  Sometime around touchdown I get GPS back ... I'm not really looking until taxiway, so don't know when, but ON the ground GPS seems to always be able to  acquire.



Two recent sample flights.  

Depart both GPSs working, then 40 minutes into flight, both drop GPS at about same time.  This is a 2:20 flight.  After another 30 minutes, 430 picks up satellites and maintains through rest of flight.  The 396 doesn't pick up satellites until back on the ground.



Return flight, both GPSs working on ground.  Sometime around 30-40 minutes into flight, both drop GPS at about same time.  After 1 hour - 1:15, the 396 reacquires satellites.  The 430 never reacquires until back on ground.



Notes:

* The 396 is new to me.  I had borrowed it previously on occasion and had similar occurrence twice.  This was a few years back and, if I recall, both occurrences were an hour or more into flight.

* The 430 was recently upgraded from 430 to 430W, but I'm still flying on the 430 antenna.  As stated above, had problem before, but it seems MUCH more  consistent now.

* I had flight following on one of these occurrences and asked center if there was know problem.  Answer was NO and about 3 planes on station reported no problems.

* Both flights above, there was much humidity in the air and I was under a lowish cloud deck.  I don't recall conditions on previous events.

* I've tried using 396 plugged into cigarette lighter and running only on battery and it makes no difference.



Any thoughts?



Thanks,

Jeff



 



         [quote][b]

rlborger(at)mac.com
Guest

Posted: Tue Aug 24, 2010 5:07 am Post subject: GPS outage in fiberglass plane

Jeff,



First, you need to upgrade the antenna on the 430 to a WAAS antenna and ensure the antenna cable length is correct for proper performance of the 430.

Now, on to the GPS signal problem.  Some questions:

1. What are you using for the 396 antenna?  Rod attached to the 396 or a remote antenna? If a remote antenna, what type?

2. Are the two units using a single antenna or do each have their own antenna?  

3. How and where is/are the antenna/s located and mounted?

4. How is/are the antenna/s cabling routed?  Looking for pinches or other defects in routing which could cause intermittent failures.

5. What is the condition of the antenna cable connection to the GPS units?

Perhaps answers to these will help the troubleshoot.

Good luck,

 Bob Borger

Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S

http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232

http://www.biplaneforumgallery.com/index.php?cat=10046

Europa Flying!

3705 Lynchburg Dr.

Corinth, TX  76208

Home:  940-497-2123

Cel:  817-992-1117





 

 

On Aug 24, 2010, at 5:54, Jeffrey Bougher wrote:

 	  Quote: 	
		  I fly a purchased Velocity.  I'm about 1/3 through Bob's book and generally not good with electrical issues - hence the book.  What I have learned is that there is a lot of knowledge on this board.



I have the following problem.  On the ground, panel mounted Garmin 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes and I lose GPS signal on both almost simultaneously.  Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I get GPS signal back it is intermittent.  When I look at the 396 GPS page, it doesn't show ANY signal on ANY satellite.  Sometime around touchdown I get GPS back ... I'm not really looking until taxiway, so don't know when, but ON the ground GPS seems to always be able to acquire.



Two recent sample flights.  

Depart both GPSs working, then 40 minutes into flight, both drop GPS at about same time.  This is a 2:20 flight.  After another 30 minutes, 430 picks up satellites and maintains through rest of flight.  The 396 doesn't pick up satellites until back on the ground.



Return flight, both GPSs working on ground.  Sometime around 30-40 minutes into flight, both drop GPS at about same time.  After 1 hour - 1:15, the 396 reacquires satellites.  The 430 never reacquires until back on ground.



Notes:

* The 396 is new to me.  I had borrowed it previously on occasion and had similar occurrence twice.  This was a few years back and, if I recall, both occurrences were an hour or more into flight.

* The 430 was recently upgraded from 430 to 430W, but I'm still flying on the 430 antenna.  As stated above, had problem before, but it seems MUCH more consistent now.

* I had flight following on one of these occurrences and asked center if there was know problem.  Answer was NO and about 3 planes on station reported no problems.

* Both flights above, there was much humidity in the air and I was under a lowish cloud deck.  I don't recall conditions on previous events.

* I've tried using 396 plugged into cigarette lighter and running only on battery and it makes no difference.



Any thoughts?



Thanks,

Jeff



 	  Quote: 	
		  



href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/contribution

jay(at)horriblehyde.com
Guest

Posted: Tue Aug 24, 2010 6:15 am Post subject: GPS outage in fiberglass plane

Something else that you might want to look at is the antenna cable length; in the MGL instrument this is a very specific length that comes already prepared with the antenna.  The instructions say not to cut this but to bundle it; some people do cut the cable and shorten it but this seriously degrades the performance of the GPS as the cable is a tuned length.  

Not sure if this applies to other GPS makes but its likely, so check that the cable is as per the original factory specification.  

   

Jay  

         

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert Borger

 Sent: 24 August 2010 03:05 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: GPS outage in fiberglass plane  

  

   

Jeff,    

   

    

First, you need to upgrade the antenna on the 430 to a WAAS antenna and ensure the antenna cable length is correct for proper performance of the 430.  

    

   

    

Now, on to the GPS signal problem.  Some questions:  

    

1. What are you using for the 396 antenna?  Rod attached to the 396 or a remote antenna? If a remote antenna, what type?  

    

2. Are the two units using a single antenna or do each have their own antenna?    

    

3. How and where is/are the antenna/s located and mounted?  

    

4. How is/are the antenna/s cabling routed?  Looking for pinches or other defects in routing which could cause intermittent failures.  

    

5. What is the condition of the antenna cable connection to the GPS units?  

    

   

    

Perhaps answers to these will help the troubleshoot.  

    

   

    

Good luck,                          

Bob Borger  

    

Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S  

    

http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232  

    

http://www.biplaneforumgallery.com/index.php?cat=10046  

    

Europa Flying!  

    

3705 Lynchburg Dr.  

    

Corinth,  TX  76208  

    

Home:  940-497-2123  

    

Cel:  817-992-1117  

    

   

  

  

  

  

  

  

  

  

  

  

   

    



 

   

    

       

On Aug 24, 2010, at 5:54, Jeffrey Bougher wrote:  

  



 

         

I fly a purchased Velocity.  I'm about 1/3 through Bob's book and generally not good with electrical issues - hence the book.  What I have learned is that there is a lot of knowledge on this board.

 

 I have the following problem.  On the ground, panel mounted Garmin 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes and I lose GPS signal on both almost simultaneously.  Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I get GPS signal back it is intermittent.  When I look at the 396 GPS page, it doesn't show ANY signal on ANY satellite.  Sometime around touchdown I get GPS back ... I'm not really looking until taxiway, so don't know when, but ON the ground GPS seems to always be able to acquire.

 

 Two recent sample flights.  

 Depart both GPSs working, then 40 minutes into flight, both drop GPS at about same time.  This is a 2:20 flight.  After another 30 minutes, 430 picks up satellites and maintains through rest of flight.  The 396 doesn't pick up satellites until back on the ground.

 

 Return flight, both GPSs working on ground.  Sometime around 30-40 minutes into flight, both drop GPS at about same time.  After 1 hour - 1:15, the 396 reacquires satellites.  The 430 never reacquires until back on ground.

 

 Notes:

 * The 396 is new to me.  I had borrowed it previously on occasion and had similar occurrence twice.  This was a few years back and, if I recall, both occurrences were an hour or more into flight.

 * The 430 was recently upgraded from 430 to 430W, but I'm still flying on the 430 antenna.  As stated above, had problem before, but it seems MUCH more consistent now.

 * I had flight following on one of these occurrences and asked center if there was know problem.  Answer was NO and about 3 planes on station reported no problems.

 * Both flights above, there was much humidity in the air and I was under a lowish cloud deck.  I don't recall conditions on previous events.

 * I've tried using 396 plugged into cigarette lighter and running only on battery and it makes no difference.

 

 Any thoughts?

 

 Thanks,

 Jeff  

  

  

    	  Quote: 	
		    href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-Listhref="http://forums.matronics.com">http://forums.matronics.comhref="http://www.matronics.com/contribution">http://www.matronics.com/contribution 	


  

   

  

   

  

       [quote][b]

grosseair(at)comcast.net
Guest

Posted: Tue Aug 24, 2010 6:39 am Post subject: GPS outage in fiberglass plane

I don't think it would affect the 396, but I don't understand why your 

avionics shop would leave the original antenna in place. It is not the 

same as the antenna for the 430W and I'm surprised it works at all.



John Grosse



Jay Hyde wrote:

 	  Quote: 	
		  

 Something else that you might want to look at is the antenna cable 

 length; in the MGL instrument this is a very specific length that 

 comes already prepared with the antenna.  The instructions say not to 

 cut this but to bundle it; some people do cut the cable and shorten it 

 but this seriously degrades the performance of the GPS as the cable is 

 a tuned length.



 Not sure if this applies to other GPS makes but its likely, so check 

 that the cable is as per the original factory specification.



 Jay



 ------------------------------------------------------------------------



 *From:* owner-aeroelectric-list-server(at)matronics.com 

 [mailto:owner-aeroelectric-list-server(at)matronics.com] *On Behalf Of 

 *Robert Borger

 *Sent:* 24 August 2010 03:05 PM

 *To:* aeroelectric-list(at)matronics.com

 *Subject:* Re: GPS outage in fiberglass plane



 Jeff,



 First, you need to upgrade the antenna on the 430 to a WAAS antenna 

 and ensure the antenna cable length is correct for proper performance 

 of the 430.



 Now, on to the GPS signal problem.  Some questions:



 1. What are you using for the 396 antenna?  Rod attached to the 396 or 

 a remote antenna? If a remote antenna, what type?



 2. Are the two units using a single antenna or do each have their own 

 antenna?



 3. How and where is/are the antenna/s located and mounted?



 4. How is/are the antenna/s cabling routed?  Looking for pinches or 

 other defects in routing which could cause intermittent failures.



 5. What is the condition of the antenna cable connection to the GPS units?



 Perhaps answers to these will help the troubleshoot.



 Good luck,



 Bob Borger



 Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S



 http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232



 http://www.biplaneforumgallery.com/index.php?cat=10046



 Europa Flying!



 3705 Lynchburg Dr.



 Corinth, TX 76208



 Home:  940-497-2123



 Cel:  817-992-1117



 On Aug 24, 2010, at 5:54, Jeffrey Bougher wrote:



 I fly a purchased Velocity.  I'm about 1/3 through Bob's book and 

 generally not good with electrical issues - hence the book.  What I 

 have learned is that there is a lot of knowledge on this board.



 I have the following problem.  On the ground, panel mounted Garmin 430 

 and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes 

 and I lose GPS signal on both almost simultaneously.  Sometimes I get 

 GPS signal back, sometimes I don't.  Sometimes when I get GPS signal 

 back it is intermittent.  When I look at the 396 GPS page, it doesn't 

 show ANY signal on ANY satellite.  Sometime around touchdown I get GPS 

 back ... I'm not really looking until taxiway, so don't know when, but 

 ON the ground GPS seems to always be able to acquire.



 Two recent sample flights.

 Depart both GPSs working, then 40 minutes into flight, both drop GPS 

 at about same time.  This is a 2:20 flight.  After another 30 minutes, 

 430 picks up satellites and maintains through rest of flight.  The 396 

 doesn't pick up satellites until back on the ground.



 Return flight, both GPSs working on ground.  Sometime around 30-40 

 minutes into flight, both drop GPS at about same time.  After 1 hour - 

 1:15, the 396 reacquires satellites.  The 430 never reacquires until 

 back on ground.



 Notes:

 * The 396 is new to me.  I had borrowed it previously on occasion and 

 had similar occurrence twice.  This was a few years back and, if I 

 recall, both occurrences were an hour or more into flight.

 * The 430 was recently upgraded from 430 to 430W, but I'm still flying 

 on the 430 antenna.  As stated above, had problem before, but it seems 

 MUCH more consistent now.

 * I had flight following on one of these occurrences and asked center 

 if there was know problem.  Answer was NO and about 3 planes on 

 station reported no problems.

 * Both flights above, there was much humidity in the air and I was 

 under a lowish cloud deck.  I don't recall conditions on previous events.

 * I've tried using 396 plugged into cigarette lighter and running only 

 on battery and it makes no difference.



 Any thoughts?



 Thanks,

 Jeff



 *  *

 *  *

 *href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List*

 *href="http://forums.matronics.com">http://forums.matronics.com*

 *href="http://www.matronics.com/contribution">http://www.matronics.com/contribution*

 *  *



 *

 *

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Tue Aug 24, 2010 7:06 am Post subject: GPS outage in fiberglass plane

The most common cause of loss of satellites (besides military jamming) 

is com or nav frequencies that interfere from other radios in the 

cockpit. The AC20-138A for GPS install calls out the frequencies that 

must be tested before a unit can be signed off in the aircraft.

On 8/24/2010 7:24 AM, John Grosse wrote:

 	  Quote: 	
		   

 <grosseair(at)comcast.net>



 I don't think it would affect the 396, but I don't understand why your 

 avionics shop would leave the original antenna in place. It is not the 

 same as the antenna for the 430W and I'm surprised it works at all.



 John Grosse



 Jay Hyde wrote:

>

> Something else that you might want to look at is the antenna cable 

> length; in the MGL instrument this is a very specific length that 

> comes already prepared with the antenna.  The instructions say not to 

> cut this but to bundle it; some people do cut the cable and shorten 

> it but this seriously degrades the performance of the GPS as the 

> cable is a tuned length.

>

> Not sure if this applies to other GPS makes but its likely, so check 

> that the cable is as per the original factory specification.

>

> Jay

>

> ------------------------------------------------------------------------

>

> *From:* owner-aeroelectric-list-server(at)matronics.com 

> [mailto:owner-aeroelectric-list-server(at)matronics.com] *On Behalf Of 

> *Robert Borger

> *Sent:* 24 August 2010 03:05 PM

> *To:* aeroelectric-list(at)matronics.com

> *Subject:* Re: GPS outage in fiberglass plane

>

> Jeff,

>

> First, you need to upgrade the antenna on the 430 to a WAAS antenna 

> and ensure the antenna cable length is correct for proper performance 

> of the 430.

>

> Now, on to the GPS signal problem.  Some questions:

>

> 1. What are you using for the 396 antenna?  Rod attached to the 396 

> or a remote antenna? If a remote antenna, what type?

>

> 2. Are the two units using a single antenna or do each have their own 

> antenna?

>

> 3. How and where is/are the antenna/s located and mounted?

>

> 4. How is/are the antenna/s cabling routed?  Looking for pinches or 

> other defects in routing which could cause intermittent failures.

>

> 5. What is the condition of the antenna cable connection to the GPS 

> units?

>

> Perhaps answers to these will help the troubleshoot.

>

> Good luck,

>

> Bob Borger

>

> Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S

>

> http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232

>

> http://www.biplaneforumgallery.com/index.php?cat=10046

>

> Europa Flying!

>

> 3705 Lynchburg Dr.

>

> Corinth, TX 76208

>

> Home:  940-497-2123

>

> Cel:  817-992-1117

>

> On Aug 24, 2010, at 5:54, Jeffrey Bougher wrote:

>

> I fly a purchased Velocity.  I'm about 1/3 through Bob's book and 

> generally not good with electrical issues - hence the book.  What I 

> have learned is that there is a lot of knowledge on this board.

>

> I have the following problem.  On the ground, panel mounted Garmin 

> 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 

> minutes and I lose GPS signal on both almost simultaneously.  

> Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I 

> get GPS signal back it is intermittent.  When I look at the 396 GPS 

> page, it doesn't show ANY signal on ANY satellite.  Sometime around 

> touchdown I get GPS back ... I'm not really looking until taxiway, so 

> don't know when, but ON the ground GPS seems to always be able to 

> acquire.

>

> Two recent sample flights.

> Depart both GPSs working, then 40 minutes into flight, both drop GPS 

> at about same time.  This is a 2:20 flight.  After another 30 

> minutes, 430 picks up satellites and maintains through rest of 

> flight.  The 396 doesn't pick up satellites until back on the ground.

>

> Return flight, both GPSs working on ground.  Sometime around 30-40 

> minutes into flight, both drop GPS at about same time.  After 1 hour 

> - 1:15, the 396 reacquires satellites.  The 430 never reacquires 

> until back on ground.

>

> Notes:

> * The 396 is new to me.  I had borrowed it previously on occasion and 

> had similar occurrence twice.  This was a few years back and, if I 

> recall, both occurrences were an hour or more into flight.

> * The 430 was recently upgraded from 430 to 430W, but I'm still 

> flying on the 430 antenna.  As stated above, had problem before, but 

> it seems MUCH more consistent now.

> * I had flight following on one of these occurrences and asked center 

> if there was know problem.  Answer was NO and about 3 planes on 

> station reported no problems.

> * Both flights above, there was much humidity in the air and I was 

> under a lowish cloud deck.  I don't recall conditions on previous 

> events.

> * I've tried using 396 plugged into cigarette lighter and running 

> only on battery and it makes no difference.

>

> Any thoughts?

>

> Thanks,

> Jeff

>

> *  *

> *  *

> *href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List* 

>

> *href="http://forums.matronics.com">http://forums.matronics.com*

> *href="http://www.matronics.com/contribution">http://www.matronics.com/contribution* 

>

> *  *

>

> *

> *

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

sportav8r(at)gmail.com
Guest

Posted: Tue Aug 24, 2010 7:08 am Post subject: GPS outage in fiberglass plane

Jeff, I've had interference issues when two GPS active patch antennas were co-located on the glareshield - neither would acquire until one was turned off or moved a good bit away.  I figured out what was up when I added the second GPS antenna (for an APRS tracker) and the Garmin 296 suddenly went "blind."  Locating the tracker GPS puck antenna in the aft baggage area (perhaps 3.5 feet line of sight from the Garmin antenna) has completely solved the issue.  Just a thought. Not sure why your problem only appears once airborne - that is most curious. 



Bill Boyd

RV-6A



On Tue, Aug 24, 2010 at 6:54 AM, Jeffrey Bougher <jsbougher(at)yahoo.com (jsbougher(at)yahoo.com)> wrote:

 [quote]I fly a purchased Velocity.  I'm about 1/3 through Bob's book and generally not good with electrical issues - hence the book.  What I have learned is that there is a lot of knowledge on this board.

 

I have the following problem.  On the ground, panel mounted Garmin 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes and I lose GPS signal on both almost simultaneously.  Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I get GPS signal back it is intermittent.  When I look at the 396 GPS page, it doesn't show ANY signal on ANY satellite.  Sometime around touchdown I get GPS back ... I'm not really looking until taxiway, so don't know when, but ON the ground GPS seems to always be able to  acquire.



Two recent sample flights.  

Depart both GPSs working, then 40 minutes into flight, both drop GPS at about same time.  This is a 2:20 flight.  After another 30 minutes, 430 picks up satellites and maintains through rest of flight.  The 396 doesn't pick up satellites until back on the ground.

 

Return flight, both GPSs working on ground.  Sometime around 30-40 minutes into flight, both drop GPS at about same time.  After 1 hour - 1:15, the 396 reacquires satellites.  The 430 never reacquires until back on ground.

 

Notes:

* The 396 is new to me.  I had borrowed it previously on occasion and had similar occurrence twice.  This was a few years back and, if I recall, both occurrences were an hour or more into flight.

* The 430 was recently upgraded from 430 to 430W, but I'm still flying on the 430 antenna.  As stated above, had problem before, but it seems MUCH more  consistent now.

* I had flight following on one of these occurrences and asked center if there was know problem.  Answer was NO and about 3 planes on station reported no problems.

* Both flights above, there was much humidity in the air and I was under a lowish cloud deck.  I don't recall conditions on previous events.

 * I've tried using 396 plugged into cigarette lighter and running only on battery and it makes no difference.



Any thoughts?



Thanks,

Jeff



 



          	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


[b]

tim2542(at)sbcglobal.net
Guest

Posted: Tue Aug 24, 2010 7:14 am Post subject: GPS outage in fiberglass plane

First, the 430W antenna is not compatible with the 430 and the fact that you had a problem before pretty much narrows it down to a bad and/or incorrect antenna. Where are your antennas located? What else is in close proximity to the them? I would suggest you make sure you have the correct antenna for each unit and it is placed where it will not be next to other electrical devices and has a good view of the sky. Fiberglass should only attenuate the signal very slightly and for our purposes can be considered not there. Assuming there is not some kind of special coatings on the glass. I’m just guessing here but could you have the 2 antennas mixed up?   

Tim Andres  

     

 (rnbraud(at)yahoo.com)   

        

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Jeffrey Bougher

 Sent: Tuesday, August 24, 2010 3:54 AM

 To: aeroelectric-list(at)matronics.com

 Subject: GPS outage in fiberglass plane  

  

       

I fly a purchased Velocity.  I'm about 1/3 through Bob's book and generally not good with electrical issues - hence the book.  What I have learned is that there is a lot of knowledge on this board.

 

 I have the following problem.  On the ground, panel mounted Garmin 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes and I lose GPS signal on both almost simultaneously.  Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I get GPS signal back it is intermittent.  When I look at the 396 GPS page, it doesn't show ANY signal on ANY satellite.  Sometime around touchdown I get GPS back ... I'm not really looking until taxiway, so don't know when, but ON the ground GPS seems to always be able to acquire.

 

 Two recent sample flights.  

 Depart both GPSs working, then 40 minutes into flight, both drop GPS at about same time.  This is a 2:20 flight.  After another 30 minutes, 430 picks up satellites and maintains through rest of flight.  The 396 doesn't pick up satellites until back on the ground.

 

 Return flight, both GPSs working on ground.  Sometime around 30-40 minutes into flight, both drop GPS at about same time.  After 1 hour - 1:15, the 396 reacquires satellites.  The 430 never reacquires until back on ground.

 

 Notes:

 * The 396 is new to me.  I had borrowed it previously on occasion and had similar occurrence twice.  This was a few years back and, if I recall, both occurrences were an hour or more into flight.

 * The 430 was recently upgraded from 430 to 430W, but I'm still flying on the 430 antenna.  As stated above, had problem before, but it seems MUCH more consistent now.

 * I had flight following on one of these occurrences and asked center if there was know problem.  Answer was NO and about 3 planes on station reported no problems.

 * Both flights above, there was much humidity in the air and I was under a lowish cloud deck.  I don't recall conditions on previous events.

 * I've tried using 396 plugged into cigarette lighter and running only on battery and it makes no difference.

 

 Any thoughts?

 

 Thanks,

 Jeff  

  

  

    	  Quote: 	
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   [quote][b]

mrspudandcompany(at)veriz
Guest

Posted: Tue Aug 24, 2010 8:05 am Post subject: GPS outage in fiberglass plane

 	  Quote: 	
		        On Tue, Aug 24, 2010 at 6:54 AM, Jeffrey Bougher <jsbougher(at)yahoo.com (jsbougher(at)yahoo.com)>    wrote:



    	  Quote: 	
		            I fly a purchased Velocity.  I'm about 1/3 through Bob's book and      generally not good with electrical issues - hence the book.  What I      have learned is that there is a lot of knowledge on this board.



I      have the following problem.  On the ground, panel mounted Garmin 430      and portable Garmin 396 work fine.  Take-off and fly for 20-45 minutes      and I lose GPS signal on both almost simultaneously.  Sometimes I get      GPS signal back, sometimes I don't.  Sometimes when I get GPS signal      back it is intermittent.  When I look at the 396 GPS page, it doesn't      show ANY signal on ANY satellite.  Sometime around touchdown I get GPS      back ... I'm not really looking until taxiway, so don't know when, but ON      the ground GPS seems to always be able to      acquire.



Thanks,

Jeff

      	  Quote: 	
		         My thought would be to operate your GPS on it's        inernal battery, and when it fails, turn off your master switch to kill        everything electrical, so the only thing still running is the engine. If        the GPS comes back, then it is probably something in the panel, if it        doesn't start working then the problem may be in the GPS.  If it is        in the panel, you can then go through a process of elimination by        restoring power  to the panel and shutting down each electronic        device individually until the problem goes away.

Roger       



	
	


	
   [quote][b]

jsbougher(at)yahoo.com
Guest

Posted: Tue Aug 24, 2010 12:55 pm Post subject: GPS outage in fiberglass plane

Nope, separate antennas.  This is what baffles me.  The only think they share in common is that they are GPSs, they are made by Garmin and they are in my plane :^).  That is why I made sure on one trip that the 396 was not even plugged into the cigarette lighter - still lost signal at same time as 430.

Jeff

From: S. Ramirez <simon(at)synchdes.com>

To: aeroelectric-list(at)matronics.com

Cc: Jeffrey Bougher  <jsbougher(at)yahoo.com>

Sent: Tue, August 24, 2010 7:24:46 AM

Subject: Re: GPS outage in fiberglass plane



                        Since both units drop out at         the same time, Jeff, I will assume that they share the same         antenna and thus lose signal somehow, probably due to         vibration.  Can you please confirm that the 430 and 396 are         using the same antenna?

         

         Thanks.

         

         Simon Ramirez

         Oviedo, FL  USA

         

       

     On 8/24/2010 6:54 AM, Jeffrey Bougher wrote:     [quote]                       I fly a purchased Velocity.  I'm about 1/3 through Bob's           book and generally not good with electrical issues - hence the           book.  What I have learned is that there is a lot of knowledge           on this board.

           

           I have the following problem.  On the ground, panel mounted           Garmin 430 and portable Garmin 396 work fine.  Take-off and           fly for 20-45 minutes and I lose GPS signal on both almost           simultaneously.  Sometimes I get GPS signal back, sometimes I           don't.  Sometimes when I get GPS signal back it is           intermittent.  When I look at the 396 GPS page, it doesn't           show ANY signal on ANY satellite.  Sometime around touchdown I           get GPS back ... I'm not really looking until taxiway, so           don't know when, but ON the ground GPS seems to always be able           to acquire.

           

           Two recent sample flights.  

           Depart both GPSs working, then 40 minutes into flight, both           drop GPS at about same time.  This is a 2:20 flight.  After           another 30 minutes, 430 picks up satellites and maintains           through rest of flight.  The 396 doesn't pick up satellites           until back on the ground.

           

           Return flight, both GPSs working on ground.  Sometime around           30-40 minutes into flight, both drop GPS at about same time.            After 1 hour - 1:15, the 396 reacquires satellites.  The 430           never reacquires until back on ground.

           

           Notes:

           * The 396 is new to me.  I had borrowed it previously on           occasion and had similar occurrence twice.  This was a few           years back and, if I recall, both occurrences were an hour or           more into flight.

           * The 430 was recently upgraded from 430 to 430W, but I'm           still flying on the 430 antenna.  As stated above, had problem           before, but it seems MUCH more consistent now.

           * I had flight following on one of these occurrences and asked           center if there was know problem.  Answer was NO and about 3           planes on station reported no problems.

           * Both flights above, there was much humidity in the air and I           was under a lowish cloud deck.  I don't recall conditions on           previous events.

           * I've tried using 396 plugged into cigarette lighter and           running only on battery and it makes no difference.

           

           Any thoughts?

           

           Thanks,

           Jeff

         

       

       

        	  Quote: 	
		  

	
     [b]

dave.gribble(at)mchsi.com
Guest

Posted: Tue Aug 24, 2010 1:43 pm Post subject: GPS outage in fiberglass plane

I had a similar problem with my 496.  It worked perfectly, but every once in a while would lose sall atellites and they would stay gone (no signal bars) for minutes at a time - even many minutes.



I didn't spend a lot of time worrying about it since my plane is VFR and I can live without the GPS in the local area.  One time I was far from home and it happened and that is how I stumbled on the problem.  I had to revert to VOR navigation and while I was tuning the NAV radio I noticed that I could make the GPS signal come back.  I noticed that when I tuned the NAV2 VOR receiver in my plane to 114.1 (or any frequency around it) that would completely kill the GPS.  All other VOR frequencies worked fine.  Sometimes it would be completely killed, and sometimes small bars would remain.



What must be happening is that the local oscialltor in the TKM nav radio must have a harmonic that lands right on the GPS frequency.  You could watch the signal bars go away on the GPS when you tuned the NAV radio.  The handheld antenna on the 496 wasn't helping things, since I was able to show that that was how the interference was getting into the GPS.



I suspect some other piece of equipment in your plane is interfering with your GPS.  When the GPS(s) fail, start turning things off or tuning them to different frequencies.  You'll find it.

Good Luck,



dave



---

rmitch1(at)hughes.net
Guest

Posted: Tue Aug 24, 2010 2:22 pm Post subject: GPS outage in fiberglass plane

Also the coax on the 430w is much higher quality shielding than that a called out in the 430 install.  If you don't have the 430w antenna, you really don't have a 430w!

Bob Mitchell

Twin comanche 42tp

Garmin 430w

Garmin 496



Sent from my iPad



On Aug 24, 2010, at 4:40 PM, dave.gribble(at)mchsi.com wrote:



[quote] 

 

 I had a similar problem with my 496.  It worked perfectly, but every once in a while would lose sall atellites and they would stay gone (no signal bars) for minutes at a time - even many minutes.

 

 I didn't spend a lot of time worrying about it since my plane is VFR and I can live without the GPS in the local area.  One time I was far from home and it happened and that is how I stumbled on the problem.  I had to revert to VOR navigation and while I was tuning the NAV radio I noticed that I could make the GPS signal come back.  I noticed that when I tuned the NAV2 VOR receiver in my plane to 114.1 (or any frequency around it) that would completely kill the GPS.  All other VOR frequencies worked fine.  Sometimes it would be completely killed, and sometimes small bars would remain.

 

 What must be happening is that the local oscialltor in the TKM nav radio must have a harmonic that lands right on the GPS frequency.  You could watch the signal bars go away on the GPS when you tuned the NAV radio.  The handheld antenna on the 496 wasn't helping things, since I was able to show that that was how the interference was getting into the GPS.

 

 I suspect some other piece of equipment in your plane is interfering with your GPS.  When the GPS(s) fail, start turning things off or tuning them to different frequencies.  You'll find it.

 

 

 Good Luck,

 

 dave

 

 ---

jsbougher(at)yahoo.com
Guest

Posted: Wed Aug 25, 2010 3:10 am Post subject: GPS outage in fiberglass plane

Wow, thanks for all the comments and suggestions ... I had to get a notepad out to write them all down.  I think I have answers to most questions.  To troubleshoot, two suggestions that I'm definitely going to follow are:

1) Move the 396 antenna further from 430 antenna - I'll stick in armpit pocket in back seat - nothing but think fiberglass and some fabric between it and sky.

2) Next time it occurs, try changing radio frequencies one by one, I will include transponder.  If this doesn't work, try killing each radio sequentially to see if that helps.

3) If above doesn't work, kill all electric and see if 396 picks up satellites.



Now, to answer a few questions and see if this brings more light to the problem:

* When I had 430W upgrade, I got new antenna.  The  puck mount is a smidge different so I need to modify mount on plane.  Avionics shop said 430 would work fine with old antenna, but it wouldn't be a 430W.  

* The 430 antenna is mounted directly under the front access panel.  It is probably within 1 foot of battery and ELT antenna.  The 396 antenna is a Garmin remote antenna and sits on the glare shield - maybe 2 feet horizontally from the 430 antenna.

* The 430 antenna has a pretty straight shot directly to radio.  Cable was fabricated by avionics shop.  It was replaced about 5 years ago when I had complete GPS failure due to bad wire ... mode this time is different (intermittent).  The 396 antenna is also 5 years old, but in a little worse shape since it is not mounted and gets handled much more.  The 

* The 396 antenna sits immediately next to the XM antenna on the glare shield.  Both are routes somewhat haphazardly around the edge of the  glareshield.  I would say they are trapped between edge of glareshield and sidewall, but they are not pinched.  The 396 cable has never been modified



Final note, my experience means that I don't really trust GPS.  I've stayed pretty good at flying VORs and always have 2 flight plans on my knee board - direct and VOR.  Fortunately, I have a DME which makes VOR flying much easier.  Unfortunately I don't have an RNAV like I used to have in my Cessna.  I LOVED the RNAV and was going to put one in my Velocity, but had several people tell me they were maintenance nightmares.  So far, the 430 has been the most troublesome part of my aircraft ownership experience.  When it works it is all sugar and sunshine, when it goes out, it back to the VORs.



     On 8/24/2010 6:54 AM, Jeffrey Bougher wrote:     [quote]                       I fly a purchased Velocity.  I'm about 1/3 through Bob's           book and generally not good with electrical issues - hence the           book.  What I have learned is that there is a lot of knowledge           on this board.

           

           I have the following problem.  On the ground, panel mounted           Garmin 430 and portable Garmin 396 work fine.  Take-off and           fly for 20-45 minutes and I lose GPS signal on both almost           simultaneously.  Sometimes I get GPS signal back, sometimes I           don't.  Sometimes when I get GPS signal back it is           intermittent.  When I look at the 396 GPS page, it doesn't           show ANY signal on ANY satellite.  Sometime around touchdown I           get GPS back ... I'm not really looking until taxiway, so           don't know when, but ON the ground GPS seems to always be able           to acquire.

           

           Two recent sample flights.  

           Depart both GPSs working, then 40 minutes into flight, both           drop GPS at about same time.  This is a 2:20 flight.  After           another 30 minutes, 430 picks up satellites and maintains           through rest of flight.  The 396 doesn't pick up satellites           until back on the ground.

           

           Return flight, both GPSs working on ground.  Sometime around           30-40 minutes into flight, both drop GPS at about same time.            After 1 hour - 1:15, the 396 reacquires satellites.  The 430           never reacquires until back on ground.

           

           Notes:

           * The 396 is new to me.  I had borrowed it previously on           occasion and had similar occurrence twice.  This was a few           years back and, if I recall, both occurrences were an hour or           more into flight.

           * The 430 was recently upgraded from 430 to 430W, but I'm           still flying on the 430 antenna.  As stated above, had problem           before, but it seems MUCH more consistent now.

           * I had flight following on one of these occurrences and asked           center if there was know problem.  Answer was NO and about 3           planes on station reported no problems.

           * Both flights above, there was much humidity in the air and I           was under a lowish cloud deck.  I don't recall conditions on           previous events.

           * I've tried using 396 plugged into cigarette lighter and           running only on battery and it makes no difference.

           

           Any thoughts?

           

           Thanks,

           Jeff

         

       

       

        	  Quote: 	
		  

	
     [b]

MauleDriver(at)nc.rr.com
Guest

Posted: Wed Aug 25, 2010 6:41 am Post subject: GPS outage in fiberglass plane

I'd note that in the case of the 430W antenna (I understand you are 

using 430 antenna), a minimum level for the antenna coax is specified.  

  A straight shot may not be ideal.   The length of cable in all GPS 

antenna seems to be something to pay attention to (either reference 

installation manual or leave supplied coax alone and coil as required).

I'm amazed at your experience because it's so different from mine.  I've 

been using GPS since the very beginning (racing gliders adopted it day 

one because it circumvented some competitive rules regarding on board 

navigation).  Equipped my Maule with a certified Garmin 300XL (crude by 

430 standards), got my rating, and logged plenty of actual behind it.  

Still have a 396 in the Maule which was a signicant upgrade to the 300XL 

panel.  All of the above has performed flawlessly from day 1.  The 300XL 

was professionally installed.  The rest of it was pretty ad hoc.  I'm 

looking forward to limiting my ground based NAV to proficiency  work in 

an almost flying RV10.

You are really going to like your setup once you get it working reliably.

Bill

Jeffrey Bougher wrote:

 	  Quote: 	
		   Wow, thanks for all the comments and suggestions ... I had to get a 

 notepad out to write them all down.  I think I have answers to most 

 questions.  To troubleshoot, two suggestions that I'm definitely going 

 to follow are:

 1) Move the 396 antenna further from 430 antenna - I'll stick in 

 armpit pocket in back seat - nothing but think fiberglass and some 

 fabric between it and sky.

 2) Next time it occurs, try changing radio frequencies one by one, I 

 will include transponder.  If this doesn't work, try killing each 

 radio sequentially to see if that helps.

 3) If above doesn't work, kill all electric and see if 396 picks up 

 satellites.

 Now, to answer a few questions and see if this brings more light to 

 the problem:

 * When I had 430W upgrade, I got new antenna.  The puck mount is a 

 smidge different so I need to modify mount on plane.  Avionics shop 

 said 430 would work fine with old antenna, but it wouldn't be a 430W. 

 * The 430 antenna is mounted directly under the front access panel.  

 It is probably within 1 foot of battery and ELT antenna.  The 396 

 antenna is a Garmin remote antenna and sits on the glare shield - 

 maybe 2 feet horizontally from the 430 antenna.

 * The 430 antenna has a pretty straight shot directly to radio.  Cable 

 was fabricated by avionics shop.  It was replaced about 5 years ago 

 when I had complete GPS failure due to bad wire ... mode this time is 

 different (intermittent).  The 396 antenna is also 5 years old, but in 

 a little worse shape since it is not mounted and gets handled much 

 more.  The

 * The 396 antenna sits immediately next to the XM antenna on the glare 

 shield.  Both are routes somewhat haphazardly around the edge of the 

 glareshield.  I would say they are trapped between edge of glareshield 

 and sidewall, but they are not pinched.  The 396 cable has never been 

 modified

 Final note, my experience means that I don't really trust GPS.  I've 

 stayed pretty good at flying VORs and always have 2 flight plans on my 

 knee board - direct and VOR.  Fortunately, I have a DME which makes 

 VOR flying much easier.  Unfortunately I don't have an RNAV like I 

 used to have in my Cessna.  I LOVED the RNAV and was going to put one 

 in my Velocity, but had several people tell me they were maintenance 

 nightmares.  So far, the 430 has been the most troublesome part of my 

 aircraft ownership experience.  When it works it is all sugar and 

 sunshine, when it goes out, it back to the VORs.

 On 8/24/2010 6:54 AM, Jeffrey Bougher wrote:

> I fly a purchased Velocity.  I'm about 1/3 through Bob's book and 

> generally not good with electrical issues - hence the book.  What I 

> have learned is that there is a lot of knowledge on this board.

>

> I have the following problem.  On the ground, panel mounted Garmin 

> 430 and portable Garmin 396 work fine.  Take-off and fly for 20-45 

> minutes and I lose GPS signal on both almost simultaneously.  

> Sometimes I get GPS signal back, sometimes I don't.  Sometimes when I 

> get GPS signal back it is intermittent.  When I look at the 396 GPS 

> page, it doesn't show ANY signal on ANY satellite.  Sometime around 

> touchdown I get GPS back ... I'm not really looking until taxiway, so 

> don't know when, but ON the ground GPS seems to always be able to 

> acquire.

>

> Two recent sample flights. 

> Depart both GPSs working, then 40 minutes into flight, both drop GPS 

> at about same time.  This is a 2:20 flight.  After another 30 

> minutes, 430 picks up satellites and maintains through rest of 

> flight.  The 396 doesn't pick up satellites until back on the ground.

>

> Return flight, both GPSs working on ground.  Sometime around 30-40 

> minutes into flight, both drop GPS at about same time.  After 1 hour 

> - 1:15, the 396 reacquires satellites.  The 430 never reacquires 

> until back on ground.

>

> Notes:

> * The 396 is new to me.  I had borrowed it previously on occasion and 

> had similar occurrence twice.  This was a few years back and, if I 

> recall, both occurrences were an hour or more into flight.

> * The 430 was recently upgraded from 430 to 430W, but I'm still 

> flying on the 430 antenna.  As stated above, had problem before, but 

> it seems MUCH more consistent now.

> * I had flight following on one of these occurrences and asked center 

> if there was know problem.  Answer was NO and about 3 planes on 

> station reported no problems.

> * Both flights above, there was much humidity in the air and I was 

> under a lowish cloud deck.  I don't recall conditions on previous events.

> * I've tried using 396 plugged into cigarette lighter and running 

> only on battery and it makes no difference.

>

> Any thoughts?

>

> Thanks,

> Jeff

>

> *

> *

 *

 *

Radioflyer

Joined: 04 Feb 2009
Posts: 43
Location: Boston

Posted: Fri Aug 27, 2010 7:39 am Post subject: Re: GPS outage in fiberglass plane

This has been an interesting discussion to read through. I've had similar experiences with a Garmin 296 that had me baffled for a while. I first used my unit extensively on a Florida to Boston cross country flight in a LongEZ. Maybe I experienced a very brief lost of signal, but it was of no consequence. The unit provided excellent service. 



Then I started using it in a C172 and noticed a troubling occurence of dropouts. Tried new software, and different antenna. Eventually, I got to associate the dropouts with specific routes, some of which had known large ground antenna installations, so I thought it was just groundstation intereference. But no one I talked to seem to be experiencing GPS problems in the area. I have used the unit in another Cessna and while the dropouts were not at all as frequent, they still occurred unpredictably. I had lost faith in my GPS. 



I had learned from various sources that the navcoms could jam the GPS. So after reading this thread, I finally took the time to check this out. I had just come back from a flight during which the GPS performed flawlessly. While on the tiedown, with engine and everything running, I started to tune in the various com frequencies I use in my area. With the GPS screen set to show the sat reception bars, I quickly found that the bars would quickly pulse down to nothing when the frequency was set between 119.200 to 119.5. This was even without transmitting and it was dramatic. As it turns out,  I am usually tuned within this frequency range when flying the routes I had associated with GPS loss. 



Since the G296 seems to work well in the LongEz, but with dropouts in the Cessna, the problem is with the Cessna radio and not the GPS. Not surprisingly, different radio installations have different RF signatures and tolerances. Maybe the Cessna radio is out of spec, maybe not, but it is good to know finally, what is causing my dropouts. Now if I'm lost and the GPS drops out, I know I can change frequencies or turn off the avionics and get re-oriented.



--Jose

james(at)etravel.org
Guest

Posted: Fri Aug 27, 2010 7:53 am Post subject: GPS outage in fiberglass plane

Interesting stuff.  That's worth everyone with a GPS tucking away in

the "for future reference" part of the brain.  Thanks for taking the

time to report this info.



James



On Fri, Aug 27, 2010 at 4:39 PM, Radioflyer <skyeyecorp(at)airpost.net> wrote:

 	  Quote: 	
		   



 This has been an interesting discussion to read through. I've had similar experiences with a Garmin 296 that had me baffled for a while. I first used my unit extensively on a Florida to Boston cross country flight in a LongEZ. Maybe I experienced a very brief lost of signal, but it was of no consequence. The unit provided excellent service.



 Then I started using it in a C172 and noticed a troubling occurence of dropouts. Tried new software, and different antenna. Eventually, I got to associate the dropouts with specific routes, some of which had known large ground antenna installations, so I thought it was just groundstation intereference. But no one I talked to seem to be experiencing GPS problems in the area. I have used the unit in another Cessna and while the dropouts were not at all as frequent, they still occurred unpredictably. I had lost faith in my GPS.



 I had learned from various sources that the navcoms could jam the GPS. So after reading this thread, I finally took the time to check this out. I had just come back from a flight during which the GPS performed flawlessly. While on the tiedown, with engine and everything running, I started to tune in the various com frequencies I use in my area. With the GPS screen set to show the sat reception bars, I quickly found that the bars would quickly pulse down to nothing when the frequency was set between 119.200 to 119.5. This was even without transmitting and it was dramatic. As it turns out, Â I am usually tuned within this frequency range when flying the routes I had associated with GPS loss.



 Since the G296 seems to work well in the LongEz, but with dropouts in the Cessna, the problem is with the Cessna radio and not the GPS. Not surprisingly, different radio installations have different RF signatures and tolerances. Maybe the Cessna radio is out of spec, maybe not, but it is good to know finally, what is causing my dropouts. Now if I'm lost and the GPS drops out, I know I can change frequencies or turn off the avionics and get re-oriented.



 --Jose





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=310285#310285

checkn6

Joined: 20 Feb 2010
Posts: 14

Posted: Sat Aug 28, 2010 7:12 am Post subject: Re: GPS outage in fiberglass plane

I agree, but I am going to go one small step further and do the frequency test while on the ground the next time I go to the airport. I too have had GPS drop-out for brief periods and just thought that I had gotten a bum deal on EBAY on my little hand held Garmin 196. I still have a plan A and plan B since my little GPS is more for informational purposes only and is really a plan C.



Thanks for starting this thread.



My wife thinks I'm nuts for reading this "boring stuff" but I love learning new things and once again I found a little gem to check on.



Chris



[quote="james(at)etravel.org"]Interesting stuff.  That's worth everyone with a GPS tucking away in

the "for future reference" part of the brain.  Thanks for taking the

time to report this info.



James



While on the tiedown, with engine and everything running, I started to tune in the various com frequencies I use in my area. With the GPS screen set to show the sat reception bars, I quickly found that the bars would quickly pulse down to nothing when the frequency was set between 119.200 to 119.5. This was even without transmitting and it was dramatic. As it turns out, Â I am usually tuned within this frequency range when flying the routes I had associated with GPS loss.

Tundra10

Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario

Posted: Sun Aug 29, 2010 6:29 am Post subject: GPS outage in fiberglass plane

I will add another data point concerning radios interfering with GPS  

reception.



I recently installed a Garmin 430W in my Cessna 172 (probably doubled  

its value, but the unit will be removed for installation into the  

airplane I am building).

I worked with an avionics shop that was willing to supervise me doing  

much of the work as a learning experience - and it was !



The Garmin installation manual cautions against installing the GPS  

antenna within 4 feet of other antennas.  The cabin roof of the Cessna  

makes that goal impossible to meet.

For simplicity, we chose to re-use the same mounting location as the  

old GPS antenna, which is a foot away from the antenna of the King  

KX-175B radio.



There are a number of tests required in the Garmin installation  

manual, including transmitting with each radio on the following  

frequencies for 35 seconds, while watching the satellite reception  

screen:



121.150, 121.175, 121.200, 121.225, 121.250

131.200, 131.225, 131.250, 131.275, 131.300, 131.325, 131.350



In my case the 131MHz frequencies interfered.  Not just slightly, but  

completely killed reception of all GPS satellites.  The strength bars  

went to zero immediately.  The 430W required more than a minute to  

recover after unkeying the transmitter.



I swapped the COM antennas between the 430W and the KX-175B.  The 430W  

produced a cleaner transmission that did not interfere with GPS  

reception.  The transmissions of the KX-175B, with the antenna now 3  

feet away from the GPS antenna, only slightly interfered (lost 10-20%  

of signal strength) and did not prevent reception from even the  

marginal satellites. So problem simply resolved.



Where I fly, I rarely use frequencies in the 131MHz range, so without  

doing this test I might have happily flown for quite a number of  

hours, only to be confounded with lack of GPS navigation at some  

future point.



I recommend everyone perform this test, since it is so quite and easy to do.



Jeff Page

Dream Aircraft Tundra #10

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sun Aug 29, 2010 7:04 am Post subject: GPS outage in fiberglass plane

Keep in mind that it is not just transmitting that creates 

interference. Having the radio simply tuned to a frequency  and turned 

on can also cause the problem. There are also nav frequencies that need 

to be checked. They are not in the AC, but this site has more detail of 

documented issues for specific radio models: 

http://www.scn.org/~bk269/gps.html

On 8/29/2010 7:26 AM, Jeff Page wrote:

 	  Quote: 	
		   



 I will add another data point concerning radios interfering with GPS 

 reception.



 I recently installed a Garmin 430W in my Cessna 172 (probably doubled 

 its value, but the unit will be removed for installation into the 

 airplane I am building).

 I worked with an avionics shop that was willing to supervise me doing 

 much of the work as a learning experience - and it was !



 The Garmin installation manual cautions against installing the GPS 

 antenna within 4 feet of other antennas.  The cabin roof of the Cessna 

 makes that goal impossible to meet.

 For simplicity, we chose to re-use the same mounting location as the 

 old GPS antenna, which is a foot away from the antenna of the King 

 KX-175B radio.



 There are a number of tests required in the Garmin installation 

 manual, including transmitting with each radio on the following 

 frequencies for 35 seconds, while watching the satellite reception 

 screen:



 121.150, 121.175, 121.200, 121.225, 121.250

 131.200, 131.225, 131.250, 131.275, 131.300, 131.325, 131.350



 In my case the 131MHz frequencies interfered.  Not just slightly, but 

 completely killed reception of all GPS satellites.  The strength bars 

 went to zero immediately.  The 430W required more than a minute to 

 recover after unkeying the transmitter.



 I swapped the COM antennas between the 430W and the KX-175B.  The 430W 

 produced a cleaner transmission that did not interfere with GPS 

 reception.  The transmissions of the KX-175B, with the antenna now 3 

 feet away from the GPS antenna, only slightly interfered (lost 10-20% 

 of signal strength) and did not prevent reception from even the 

 marginal satellites. So problem simply resolved.



 Where I fly, I rarely use frequencies in the 131MHz range, so without 

 doing this test I might have happily flown for quite a number of 

 hours, only to be confounded with lack of GPS navigation at some 

 future point.



 I recommend everyone perform this test, since it is so quite and easy 

 to do.



 Jeff Page

 Dream Aircraft Tundra #10

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

raymondj(at)frontiernet.n
Guest

Posted: Sun Aug 29, 2010 12:53 pm Post subject: GPS outage in fiberglass plane

Slightly off topic.   Does anyone have any info on  similar problems 

occurring on GPS caused by marine radios?  Any info would be appreciated.



do not archive



Thanks,



Raymond Julian

Kettle River, MN

On 08/29/2010 09:26 AM, Jeff Page wrote:

 	  Quote: 	
		   



 I will add another data point concerning radios interfering with GPS 

 reception.



 I recently installed a Garmin 430W in my Cessna 172 (probably doubled 

 its value, but the unit will be removed for installation into the 

 airplane I am building).

 I worked with an avionics shop that was willing to supervise me doing 

 much of the work as a learning experience - and it was !



 The Garmin installation manual cautions against installing the GPS 

 antenna within 4 feet of other antennas.  The cabin roof of the Cessna 

 makes that goal impossible to meet.

 For simplicity, we chose to re-use the same mounting location as the 

 old GPS antenna, which is a foot away from the antenna of the King 

 KX-175B radio.



 There are a number of tests required in the Garmin installation 

 manual, including transmitting with each radio on the following 

 frequencies for 35 seconds, while watching the satellite reception 

 screen:



 121.150, 121.175, 121.200, 121.225, 121.250

 131.200, 131.225, 131.250, 131.275, 131.300, 131.325, 131.350



 In my case the 131MHz frequencies interfered.  Not just slightly, but 

 completely killed reception of all GPS satellites.  The strength bars 

 went to zero immediately.  The 430W required more than a minute to 

 recover after unkeying the transmitter.



 I swapped the COM antennas between the 430W and the KX-175B.  The 430W 

 produced a cleaner transmission that did not interfere with GPS 

 reception.  The transmissions of the KX-175B, with the antenna now 3 

 feet away from the GPS antenna, only slightly interfered (lost 10-20% 

 of signal strength) and did not prevent reception from even the 

 marginal satellites. So problem simply resolved.



 Where I fly, I rarely use frequencies in the 131MHz range, so without 

 doing this test I might have happily flown for quite a number of 

 hours, only to be confounded with lack of GPS navigation at some 

 future point.



 I recommend everyone perform this test, since it is so quite and easy 

 to do.



 Jeff Page

 Dream Aircraft Tundra #10

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