 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Erich_Weaver(at)URSCorp.c
Guest
|
 Posted: Sun Jun 07, 2009 9:21 am Post subject: RF interference fix? |
 |
|
From first flight, the GRT EFIS and EIS on my RV have indicated momentary, anomalously high fuel pressure readings, typically just before take-off and also when entering and in the pattern. Stewed over that for over a year before asking myself the question - how does the system KNOW Im going to takeoff or land? Asking that question led me to the only possible answer: it knows because I get on comm and announce it! A couple of weeks ago I confirmed this - every comm transmission resulted in a sharp rise in fuel pressure. Yesterday I took it a step further, seeking to determine what the propogation mode was, and reasoned it was either RF interference or some sort of magnetic coupling associated with the increased power requirements during comm transmissions. The easy test was to get out my battery operated handheld transceiver and transmit from inside the cockpit with the engine running and the EFIS/EIS powered up, so I did that first. Bingo - a similar increase in the fuel pressure reading, although to a lesser degree than with ship's comm. Also noticed a lot of noise on my handheld when receiving from inside the cockpit - noise that isnt noticeable on ship's comm, nor on the handheld normally.So, now Im feeling pretty high and mighty with my diagnostic skills, but the problem still remains - where do I go from here to fix this?
thanks
erich
This e-mail and any attachments contain URS Corporation confidential information that may be proprietary or privileged. If you receive this message in error or are not the intended recipient, you should not retain, distribute, disclose or use any of this information and you should destroy the e-mail and any attachments or copies. [quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
 |
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Mon Jun 08, 2009 3:34 am Post subject: RF interference fix? |
|
|
At 11:27 AM 6/7/2009, you wrote:
From first flight, the GRT EFIS and EIS on my RV have indicated
momentary, anomalously high fuel pressure readings, typically just
before take-off and also when entering and in the pattern. Stewed
over that for over a year before asking myself the question - how
does the system KNOW Im going to takeoff or land? Asking that
question led me to the only possible answer: it knows because I get
on comm and announce it! A couple of weeks ago I confirmed this -
every comm transmission resulted in a sharp rise in fuel
pressure. Yesterday I took it a step further, seeking to determine
what the propogation mode was, and reasoned it was either RF
interference or some sort of magnetic coupling associated with the
increased power requirements during comm transmissions. The easy
test was to get out my battery operated handheld transceiver and
transmit from inside the cockpit with the engine running and the
EFIS/EIS powered up, so I did that first. Bingo - a similar increase
in the fuel pressure reading, although to a lesser degree than with
ship's comm.
This is not an uncommon problem with products
offered to the OBAM aircraft community. In the
TC aircraft world, we have to demonstrate immunity
from commonly encountered radio frquency stresses
in the lab during qualification tests.
Some of the instruments offere by Van's have
demonstrated sensitivity to VHF comm signals
from ship's transmitters.
Talk to GRT first. They have certainly
encountered this before. They know their product
better than anyone else and should be able to
recommend some filtering . . . probably compoents
added at the connector where the pressure transducer
wires come into the indicator.
Don't be surprised that there isn't a fix either.
These issues are realtively easy to fix during
prouduct development and qualification . . . but
MUCH more difficult later.
Also noticed a lot of noise on my handheld when receiving from
inside the cockpit - noise that isnt noticeable on ship's comm, nor
on the handheld normally.So, now Im feeling pretty high and mighty
with my diagnostic skills, but the problem still remains - where do I
go from here to fix this?
Igntion noise? The best way to enhance the performance
of a hand held transceiver is to provide connections to
the ship's regulator comm antenna. I used to recommend
a coiled loop of coax within reach of pilot in the
cockpit that could be opened with a pair of in-line
connectors.
http://www.aeroelectric.com/Pictures/Connectors/Coax/BNC_Cable_Female_1.jpg
http://www.aeroelectric.com/Pictures/Connectors/Coax/BNC_Cable_Male.jpg
Put the cable-male on the feeder that goes to the the
antenna and leave enough slack in it to allow connection
to the hand-held. A pair of right-angle coax adapers
http://www.aeroelectric.com/Pictures/Connectors/Coax/BNC_Rt-Angle_Adapt_2.jpg
can be used to do a small radius 180 degree turn in
the coax so that it will lay against the back of the
hand-held and exit downward.
Bob . . .
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Mon Jun 08, 2009 3:41 am Post subject: RF interference fix? |
|
|
At 06:31 AM 6/8/2009, you wrote:
| Quote: |
<nuckolls.bob(at)aeroelectric.com>
At 11:27 AM 6/7/2009, you wrote:
The easy test was to get out my battery operated handheld
transceiver and transmit from inside the cockpit with the engine
running and the EFIS/EIS powered up, so I did that first. Bingo -
a similar increase in the fuel pressure reading, although to a
lesser degree than with ship's comm.
|
P.S. You may find it more practical to live with it.
After one understands how the problem manifests itself
then it may be easier to just let it go. I've had several
customers who've elected to not pursue a best-we-know-
how-to-do fix when the $time$ associated with the
fix was going to be pretty high.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
