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  #61  
Old 02-19-2021, 10:34 AM
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bjdecker bjdecker is offline
 
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Quote:
Originally Posted by jnmeade View Post
Some thick paint (not just metallic paint) and even dirty rain when just sitting on the ground can detune these narrow-band antennas. Dirty rain is not a problem in the air because it washes off. So says a personal friend who was an antenna design engineer for Rockwell Collins for 30 years.
These are broadband, high gain, amplified, high frequency antennas...

L1 => 1575.42MHz, and the channel width is ~30MHz.

...and yes, debris on the face will attenuate the signal...
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2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
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  #62  
Old 02-19-2021, 10:37 AM
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RV7A Flyer RV7A Flyer is offline
 
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Originally Posted by Ironflight View Post
In my case “dropouts” include everything from a message on the IFD 440 saying “GPS Integrity Lost” with continued good position data for the pilot to complete loss of GPS signal and the IFD going into “Ded Reckoning” mode. Now to be completely up front, this most often happens when I have done something that the FAA “system” didn’t expect, like going upside down, which is perfectly legal, but the guys who designed ADS-B didn’t;t appear to anticipate.....

Paul
Yep...my 430W does the same thing when I go upside down, BUT the Dynon seems to chug right on through it (at least, if it loses lock, it recovers it so quickly it's never noticed or alarmed).
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  #63  
Old 02-19-2021, 02:12 PM
BobTurner BobTurner is offline
 
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The more modern systems use looking at multiple solutions, instead of RAIM, to assure ‘integrity’. 4 satellites gets you a solution; 6 or more gets you ‘integrity’.
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  #64  
Old 02-19-2021, 09:01 PM
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The more modern systems use looking at multiple solutions, instead of RAIM, to assure ‘integrity’. 4 satellites gets you a solution; 6 or more gets you ‘integrity’.
Interesting. Do they do multiple LSQs on sets of 4+ sats (or perhaps all combinations of n-1 satellites available) and then some sort of averaging of the results (or choose the solution with the lowest error)? Waaaay back when I wrote GPS software, in the days pre-WAAS, we just ran an LSQ using all available satellites to reduce DOP, but that was in the stone age by comparison to today's equipment.
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  #65  
Old 02-20-2021, 06:28 AM
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Originally Posted by RV7A Flyer View Post
Interesting. Do they do multiple LSQs on sets of 4+ sats (or perhaps all combinations of n-1 satellites available) and then some sort of averaging of the results (or choose the solution with the lowest error)? Waaaay back when I wrote GPS software, in the days pre-WAAS, we just ran an LSQ using all available satellites to reduce DOP, but that was in the stone age by comparison to today's equipment.
"It was my understanding there would be no math..." -- Chevy Chase as Gerald R. Ford.
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Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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  #66  
Old 03-05-2021, 10:15 PM
jimgreen jimgreen is offline
 
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Having trouble finding a decent spot for a Dynon 250 as I have two top mounted antennas. Under the top cowl would be a candidate but I'm wondering about possible interference from Lightspeed ignition coils which sit rear and centre. Anyone had performance issues with this arrangement?
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  #67  
Old 03-05-2021, 10:29 PM
PilotjohnS PilotjohnS is offline
 
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Default Almost convinced myself

I have almost convinced myself to put my two gps antennas recessed in the glareshiel. With a fabric covering, it will be hard to see them but they will have a good view of the sky. This is similar to the illustration in the Garmin G3x manual. The manual says they can be close to each other (6”?) but not next to transmitting antennas( they wont be.). As in a previous post, my stretch goal is to get XM weather in Antartica. :-)

I am concerned about under the cowl because of the possible losses going thru the cowl, but the fitgher jets shot thru the radome, dont they?
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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Last edited by PilotjohnS : 03-05-2021 at 10:32 PM.
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  #68  
Old 03-06-2021, 07:56 AM
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Carl Froehlich Carl Froehlich is online now
 
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Quote:
Originally Posted by jimgreen View Post
Having trouble finding a decent spot for a Dynon 250 as I have two top mounted antennas. Under the top cowl would be a candidate but I'm wondering about possible interference from Lightspeed ignition coils which sit rear and centre. Anyone had performance issues with this arrangement?
I mounted the Dynon GPS antenna/receiver on the glare shield on three RVs. I cover it with dark cloth to eliminate glare. Works perfect.

Carl
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  #69  
Old 03-07-2021, 09:44 AM
jimgreen jimgreen is offline
 
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Thanks for the replies.This is an upgrade on a tip-up so I think I'll try the glare shield first as it is an easy placement. It's close to zero work to put it there. If the performance isn't up to scratch I'm no worse off having to move it than I am now.
I'd still like to know if proximity to electronic ignition gives any trouble with under the cowl installs.
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  #70  
Old 03-07-2021, 10:21 AM
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bjdecker bjdecker is offline
 
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Quote:
Originally Posted by jimgreen View Post
Thanks for the replies.This is an upgrade on a tip-up so I think I'll try the glare shield first as it is an easy placement. It's close to zero work to put it there. If the performance isn't up to scratch I'm no worse off having to move it than I am now.
I'd still like to know if proximity to electronic ignition gives any trouble with under the cowl installs.
Jim -

PM sent...

B
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Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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