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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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 Posted: Fri Mar 09, 2007 5:13 am Post subject: GNS 430W Antenna Requirements |
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3/9/2007
Hello List Experts, It is fairly well documented that Garmin wants high
quality antenna cable (RGU 142 or 400) to be used for the GNS 430W and it
must be between 13 and 35 feet long.
I can understand a maximum limit. I cannot understand the physics or
electronic principles behind the minimum length requirement.
Can someone please educate me? Thanks.
OC -- The best investment we can make is the effort to gather and understand
knowledge.
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BobsV35B(at)aol.com
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| Posted: Fri Mar 09, 2007 5:47 am Post subject: GNS 430W Antenna Requirements |
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Good Morning OC,
When I asked that question, I was told they need the additional attenuation supplied by the extra length. Seems kinda unusual to me, but the techie who told me that is a pretty sharp tack!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 3/9/2007 7:15:36 A.M. Central Standard Time, bakerocb(at)cox.net writes:
| Quote: | I can understand a maximum limit. I cannot understand the physics or
electronic principles behind the minimum length requirement.
Can someone please educate me? Thanks.
|
AOL now offers free email to everyone. Find out more about what's free from AOL at AOL.com.
[quote][b]
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N6030X(at)DaveMorris.com
Guest
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| Posted: Fri Mar 09, 2007 7:08 am Post subject: GNS 430W Antenna Requirements |
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I would be curious to hear the official answer for this, too, because
I've worked with antennas since 1971 and tracked amateur satellites
for many years, and I couldn't figure out initially why they would
have a minimum length. If anything, common sense would dictate they
should want it as short as possible to have as LITTLE attenuation as
possible when trying to pick up satellites that are hundreds of miles away.
But this is an amplified antenna, and the preamp is there to help
pull the satellite signal out of the noise. Once it has done that,
they need to make sure the resulting output doesn't swamp the
front-end of the GPS receiver. So they picked a length of coax that
would attenuate the signal just enough to give a clean signal at the receiver.
By using the coax as an attenuator instead of resistors inside the
receiver, if at some point during some installation it is discovered
the attenuation is too great, the installer can just slice a foot or
two off the coax and get more signal strength, and there is no need
to ship units back and forth to and from the factory to replace attenuators.
Dave Morris
(the standard Dennis Miller waivers apply)
At 07:45 AM 3/9/2007, you wrote:
| Quote: | Good Morning OC,
When I asked that question, I was told they need the additional
attenuation supplied by the extra length. Seems kinda unusual to me,
but the techie who told me that is a pretty sharp tack!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 3/9/2007 7:15:36 A.M. Central Standard Time,
bakerocb(at)cox.net writes:
I can understand a maximum limit. I cannot understand the physics or
electronic principles behind the minimum length requirement.
Can someone please educate me? Thanks.
----------
AOL now offers free email to everyone. Find out more about what's
free from AOL at <http://www.aol.com?ncid=AOLAOF00020000000339>AOL.com.
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echristley(at)nc.rr.com
Guest
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| Posted: Fri Mar 09, 2007 7:12 am Post subject: GNS 430W Antenna Requirements |
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bakerocb(at)cox.net wrote:
| Quote: |
3/9/2007
Hello List Experts, It is fairly well documented that Garmin wants
high quality antenna cable (RGU 142 or 400) to be used for the GNS
430W and it must be between 13 and 35 feet long.
I can understand a maximum limit. I cannot understand the physics or
electronic principles behind the minimum length requirement.
Can someone please educate me? Thanks.
|
Working in telecom, I get a lot of experience to fiberoptics. We often
have to insert an attenuator in the line when doing our tests. The
circuits were designed to power miles of optic cable, and if you use
just a few feet the power from the transmitter will 'saturate' the
reciever. This is akin to watching a TV in a dark room with the
brightness turned up WAY to high. Everything begins to blend together
in one big mush.
--
,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |
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Bret Smith
Joined: 09 Jan 2006
Posts: 178
Location: Mineral Bluff, GA
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| Posted: Fri Mar 09, 2007 7:54 am Post subject: GNS 430W Antenna Requirements |
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OC,
Is the minimum length cable required for both COM and NAV?
Bret Smith
RV-9A "Wings"
Blue Ridge, GA
www.FlightInnovations.com
---
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_________________
Bret Smith
RV-9A (Emp) |
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BobsV35B(at)aol.com
Guest
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| Posted: Fri Mar 09, 2007 8:03 am Post subject: GNS 430W Antenna Requirements |
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Not OC here but it is only for the GPS antenna.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 3/9/2007 9:56:41 A.M. Central Standard Time, smithhb(at)tds.net writes:
| Quote: | Is the minimum length cable required for both COM and NAV?
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[quote][b]
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