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09-10-2015, 06:33 PM
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Join Date: Nov 2013
Location: Annapolis MD
Posts: 457
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Odd BNC device
I found this device attached to the old GPS antenna in my plane. Can anyone identify it? Is it some sort of attenuator? The GPS was a Garmin 250XL.
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CA
2000 RV-8A | O-360, SDS CPI, FP, G3X Touch, VP-X, EarthX | Eastern Shore | KESN
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09-10-2015, 06:37 PM
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Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,684
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It's a small hammer..... just put it in your toolbox. 
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"Kindness is never a bad plan."
exemption option waived. Donation appropriate.
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09-10-2015, 07:09 PM
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Join Date: Mar 2005
Location: Dallas area
Posts: 11,422
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It's a notch filter to prevent the harmonics from your comm radio from interfering with your GPS.
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Mel Asberry, DAR since the last century. Over 1,000 certifications accomplished. Discount for Veterans, Law Enforcement, Fire Fighters.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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09-10-2015, 07:10 PM
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Join Date: Nov 2007
Location: Solomons, MD.
Posts: 1,276
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It is a NOTCH FILTER and is used to attenuate unwanted frequencies that may be presented to the receiver.
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Noel
RV-6A N6NF
tip-up
flying
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09-10-2015, 07:42 PM
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Join Date: Mar 2014
Location: Idaho ID40
Posts: 811
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Quote:
Originally Posted by noelf
It is a NOTCH FILTER and is used to attenuate unwanted frequencies that may be presented to the receiver.
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Yup... That's what it is |
09-10-2015, 07:48 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,884
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They are all wrong. It is a DHS tracking device! 
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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09-10-2015, 08:39 PM
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Join Date: Sep 2013
Location: Buda, TX
Posts: 56
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You put it inline with the antenna to prevent that water hammer noise you'd get if you end a radio transmission to abruptly.  |
09-10-2015, 08:58 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,975
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Quote:
Originally Posted by Mel
It's a notch filter to prevent the harmonics from your comm radio from interfering with your GPS.
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Even the later Garmin navigators need checking for this interference to meet their STC requirements.
For the early 430 units the frequencies to check are -
121.150
121.175
121.200
131.250
131.275
131.300
With the ADS-B accuracy requirements coming up you certainly don't want to lose that certified 2020 GPS position when you transmit on one of the above frequencies. 
Re-install the notch filter with your present GPS, it can't do any harm, and check your installation manual for the specific critical frequencies for your present GPS unit.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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09-10-2015, 10:01 PM
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Join Date: Nov 2013
Location: Annapolis MD
Posts: 457
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Interesting. I will reconnect it. But it raises a question about the new GPS 20A position source that I am installing. The existing antenna is mounted on the glare shield, which will feed the GPS in the GDU 460, and will serve as the backup GPS source. The new GPS antenna for the GPS 20A necessary for ADS-B integrity is mounted behind the canopy slide rail. Will it require a notch filter as well?
C.
__________________
CA
2000 RV-8A | O-360, SDS CPI, FP, G3X Touch, VP-X, EarthX | Eastern Shore | KESN
Last edited by maus92 : 09-10-2015 at 10:04 PM.
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09-10-2015, 11:53 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,975
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Quote:
Originally Posted by maus92
Interesting. I will reconnect it. But it raises a question about the new GPS 20A position source that I am installing. The existing antenna is mounted on the glare shield, which will feed the GPS in the GDU 460, and will serve as the backup GPS source. The new GPS antenna for the GPS 20A necessary for ADS-B integrity is mounted behind the canopy slide rail. Will it require a notch filter as well?
C.
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Check the installation manual for post-installation testing, but since it's a new device specifically for ADS-B compliance it probably has a good filter internally.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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