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  #11  
Old 10-24-2007, 10:22 PM
Loboflyer Loboflyer is offline
 
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Location: Albuquerque, NM
Posts: 97
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It would pain me to throw away perfectly good signal... I'm guessing this loss requirement is due to active antennas having enough gain for receiver saturation?
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Albuquerque, NM
RV-7A (Preview Plans Stage), VAF# 1149
Assisting/designing panel for flying RV-6A
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  #12  
Old 10-25-2007, 05:23 AM
pa24 pa24 is offline
 
Join Date: May 2005
Posts: 14
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Appreciate all those who have responded. I guess I'll just have to bite the bullet and spend the 25 plus bucks on one connector. I mounted my antenna forward of the firewall and used a 2 1/2 foot length of RG 400. I have yet to turn my 430w system on. I have another stupid question - how do you measure the db signal loss between antenna and receiver? If necessary, I'll run another coax and coil it according to Tony's answer but, I want to make sure I have the proper signal loss before wasting all this money.
Thanks,
Roy
RV 7 Finishing
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  #13  
Old 10-25-2007, 09:41 PM
Loboflyer Loboflyer is offline
 
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Location: Albuquerque, NM
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Quote:
Originally Posted by pa24 View Post
I have another stupid question - how do you measure the db signal loss between antenna and receiver?
Definitely not a stupid question, but I sure can't give you a smart answer. At work, we use an outrageously expensive piece of equipment called a "network analyzer" (our particular model costs over $150,000). A cheaper solution is a signal source and a power meter, but that's still way more than anyone here would spend. Without asking around, I would venture a guess that a good avionics shop would have enough stuff to kludge this measurement.

I can think of a way to do it if the GPS has a built in signal strength meter, but it would involve needing the GPS on a bench in clear sky view. Since I don't know if the minimum loss spec on the cable is related to damage levels (I doubt it, but I'm not going to risk someone else's GPS) I'm not going to post the procedure that's in my head right now without trying it first.

Cheapest solution is to look at the loss spec for the particular coax cable you have and hope they measured it right. These are usually given as dB / ft or dB / 100 ft. Adaptors and connectors will add probably no more than a couple of tenths of a dB to the cable's loss.
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  #14  
Old 10-26-2007, 10:11 AM
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atreff atreff is offline
 
Join Date: Jan 2005
Posts: 215
Default It's all in the GNS430W install manual.

Check your install manual for the 430W, in the antenna installation guidelines section, it's in there, connector and coax db loss.

Art in Asheville.
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  #15  
Old 10-26-2007, 11:49 AM
pa24 pa24 is offline
 
Join Date: May 2005
Posts: 14
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Quote:
Originally Posted by atreff View Post
Check your install manual for the 430W, in the antenna installation guidelines section, it's in there, connector and coax db loss.

Art in Asheville.
Yea, that would certainly be useful information if I had the installation manual. You are saying that you received an installation manual with your 430? Unfortunately, my unit came with pilot's reference and operating manuals only, and it's a brand new unit.
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  #16  
Old 10-26-2007, 12:47 PM
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atreff atreff is offline
 
Join Date: Jan 2005
Posts: 215
Default 430 manuals

Garmin no longer publishes install manuals on paper, soft copies (.pdf) are all available thru your dealer, I had to ask for mine.

Send me an email and I'll send you a zip file with the 430 manual in it. It' 8MB, so I have to compress it. 220+ pages.

Art in Asheville
lowflyer8@gmail.com
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  #17  
Old 03-30-2008, 11:12 AM
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Gsuit Gsuit is offline
 
Join Date: Nov 2005
Location: Beaumont, TX
Posts: 210
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Quote:
Originally Posted by Jamie View Post
My GPS antenna has a TNC connector. I simply went to Fry's and bought a TNC to BNC adapter. It works perfectly -- $2.00 and the problem solved.
Quote:
Originally Posted by az_gila View Post
Jamie... that might not be a good solution for the G-430/530 Upgrade to WAAS case.gil A
Straight from the installation manual:

NOTE
If the existing coaxial cable is terminated with a BNC connector and the GPS WAAS antenna being installed has a TNC connector, a TNC-to-BNC adapter such as P/N 1-1478013-0 from AMP (Tyco) may be used. The adapter will add 0.5 dB to the overall GPS antenna cable loss.
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RV-7 N454CH (Flying)
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  #18  
Old 03-30-2008, 11:25 AM
elippse elippse is offline
 
Join Date: Dec 2006
Location: Arroyo Grande, CA
Posts: 938
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"Penn Estimates that to replace the GPS coax will run approximately $150 - $395 depending on the aircraft and the location of the GPS antenna."

Andrew's FSJ1-50 is available for $1.29/ft, and BNC connectors are $11. Its loss is half of that of RG58, and will easily meet the loss spec. See the posting I made earlier about its use and the loss comparisons made by Mike Cherney which he posted on the canard site. By the way, the "N" and "C" in these connectors are the initials of the last names of the two guys with Bell Labs who invented these connectors around WWII. The "B" stands for bayonet, and the "T" stands for threaded.
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