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R.A. Miller Industries, Inc.

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EAA Transponder Antenna Mounting Tips Video
http://www.eaavideo.org/video.aspx?v=1136841468001

Tips for Ground Planes for Aircraft Radio Antennas
Most radio antennas require a ground plane.  The AV-534 is a good example of an antenna that performs best with a ground plane.  A ground plane is a metal surface that is connected to the antennas ground (common).  There is no need for a ground plane when mounting an antenna on a metal aircraft, but it can be tough to accommodate in a fiberglass aircraft such as a sailplane. 

Note: Radio antennas can be mounted inside a fiberglass aircraft, but they would not work well if mounted inside a carbon fiber aircraft. 

Below is a note from RAMI about ground planes for aircraft radio antennas.

A proper ground plane is one that extends 1/4 wavelength (at the operating frequency) outward in all directions from the feed point or base of the antenna. 1/4 wavelength at aircraft com frequencies is approximately 24 inches. So the ground plane would be approximately 4 ft. X 4 ft. (or 4 ft. diameter) conductive surface with the antenna mounted in the center. You can also accomplish this with (2) four foot ( 1.22 m) long conductive wires running perpendicular to each other and electrically connected to the shield of the transmission line at the base of the antenna at their mid points. Similar to a base station antenna seen at an airport terminal building. The wires can be run inside the fuselage forward and aft and down the inside wall.

Sincerely,

Ben Ennenga
Engineering Manager / GAA Product Line Manager
RAMI

Tips for Ground Planes for Transponder Antennas
I talked to Ben Ennenga at RAMI about transponder antenna ground planes.  Some interesting notes from that conversation are below.  Thank you Ben for the friendly and helpful support!

  • A ground plane is required (of course) with both rod style and blade style transponder antennas.
  • The smallest recommended ground plane would be 12 inches in diameter (6 inches radius). 
  • A ground plane works about equally well regardless of whether it is made from a solid plate (such as aluminum) or instead made using 2 wires in a "+" arrangement. In either case, the radius should be at least 6 inches.
  • When working with carbon fiber glider fuselages, the antenna must be mounted on the outside of the fuselage, but it is OK to mount the ground plane on the inside.
  • The mounting screws for the RAMI AV-74 antenna are connected to the antenna ground.  Therefore, you can connect the ground plane to either or both of the mounting screws.
  • It is OK for the ground plane wires ("+" configuration) to curve and follow the inside of the glider fuselage.

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Part # Description Photo
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Price

Lead-time
AV-22

RAMI AV-22 Rod Style Transponder Antenna

The AV-22 is a transponder antenna which utilizes a "BNC" connector that allows for a smaller mounting hole. The antenna is designed to operate at speeds up to 350 mph and altitudes up to 50,000 ft. It has a drag force of 0.41 lb @ 250 mph.

Note: The blade style antennas below are more expensive, but they have about 1/5 the drag of this rod and ball antenna.

See: Tips for Ground Planes for Transponder Antennas

Specifications 
Frequency: 1030 to 1090 MHz
Impedance: 50 Ohms Nominal
VSWR: 1.3 to 1 Maximum
Polarization: Vertical
Pattern: Omni-Directional
Connector: Type "BNC" Female
Max Weight: 1 oz
Overall Length: 3.19" (81 mm)
Outside Length: 2.44" (62 mm)
RF Power Capacity: 250 Watts Pulse
ECCN 9A991
SCHEDULE B CODE 8529.10.4000
TSO C74c
$78 In Stock
AV-74

RAMI AV-74 Blade Style Transponder or DME Antenna

Note: Most glider pilots prefer the AV-74-1 below because the longer mounting studs make it easier to mount through a sailplane fuselage.

The AV-74 is a broadband blade type antenna for transponder or DME application. The antenna housing is constructed of an acrylonitrile-styrene-acrylic (ASA) shell. The white color allows maximum performance without losses due to color pigments or unseen dirt. The antenna is supplied with cellular neoprene mounting pad and hardware. The antenna is designed to operate at speeds up to 350 mph and altitudes up to 50,000 ft. It has a drag force of 0.09 lbs @ 250 mph. This antenna is a direct replacement for Comant's model CI-105.

Length of Mounting Studs: 10 mm (0.375 in)

See: Tips for Ground Planes for Transponder Antennas

Product Sheet

Specifications 
Frequency: 960 to 1220 MHz
Impedance: 50 Ohms Nominal
VSWR: 1.5 to 1 Maximum
Connector: Type "BNC" Female
Max Weight: 0.2 Lb
Max Height: 3.4"
RF Power Capacity: 2.5 kW Peak
ECCN EAR99
SCHEDULE B CODE 8529104000
Color Gloss White
TSO C66c,C74c
$160 In Stock
AV-74-1

RAMI AV-74-1 Blade Style Transponder or DME Antenna

This antenna is like the AV-74 - but with longer mounting studs - which is nice when trying to mount it through a glider fuselage.

The AV-74 is a broadband blade type antenna for transponder or DME application. The antenna housing is constructed of an acrylonitrile-styrene-acrylic (ASA) shell. The white color allows maximum performance without losses due to color pigments or unseen dirt. The antenna is supplied with cellular neoprene mounting pad and hardware. The antenna is designed to operate at speeds up to 350 mph and altitudes up to 50,000 ft. It has a drag force of 0.09 lbs @ 250 mph. This antenna is a direct replacement for Comant's model CI-105-16.

Length of Mounting Studs: 20 mm (0.80 in)

See: Tips for Ground Planes for Transponder Antennas

Product Sheet

Specifications 
Frequency: 960 to 1220 MHz
Impedance: 50 Ohms Nominal
VSWR: 1.5 to 1 Maximum
Connector: Type "BNC" Female
Max Weight: 0.2 Lb
Max Height: 3.4"
RF Power Capacity: 2.5 kW Peak
ECCN EAR99
SCHEDULE B CODE 8529104000
Color Gloss White
TSO C66c,C74c

$181 In Stock
AV-534 Antenna, Bent Rod Style, 1/4 Wave
118 to 136 MHz (Aircraft Radio Band)
The AV-534 is a heavy-duty stainless steel quarterwave VHF communications antenna. It is manufactured with a durable type stainless steel whip and large stress-relieved ferrule and comes complete with porcelain insulators and mounting hardware. The antenna is designed to operate at speeds of up to 350 mph and altitudes of 50,000 ft. It has a drag force of 0.56 lb @ 250 mph.

See: Tips for Ground Planes for Aircraft Radio Antennas
 

Specifications 
Application:  Airborne Communications
Frequency: 118 to 137 MHz
Impedance:  50 Ohms Nominal
VSWR:  3.0 to 1 Maximum
Polarization:  Vertical
Pattern:  Omni-Directional
Connector:  N/A
Max Weight:  8 oz
Max Height:  19.5"
Mounting Hole Diameter:  0.531"
RF Power Capacity:  50 Watts

$110 In Stock

Cumulus Soaring, Inc.
Paul E. Remde

8661 Connelly Place
Savage, Minnesota 55378
USA


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