22
votes
What are these "winglets" on the roof of the 737?
In general, those are called blade antennas. They consist of a monopole antenna (a single rod sticking out of the fuselage) with an aerodynamic fairing around it.
- 10.3k
18
votes
What are these "winglets" on the roof of the 737?
It looks like a VHF and ELT antenna.
References:
Boeing 737NG Radio Equipment
Communications
- 527
12
votes
Accepted
What is the round tube mounted on the roof just behind the windshield of a PC-6?
The vertical tube on top of the cabin is the fuel system vent mast:
Pictures are taken from an online copy of Royal Australian Air Force Pilatus Porter Flight Manual, Australian Air Publication 7211....
- 30k
10
votes
Accepted
Which antenna on an commercial airline airplane is used for the transponder (SSR)?
Short answer
The SSR antennas are labeled ATC L and ATC R (two at the top, two at the bottom).
Source
Both SSR and TCAS systems use the same communication protocol and use the same frequencies (...
- 76.6k
8
votes
Why should the optimum position of GPS Antenna be close to aircraft's CG?
GPS signals need line of sight to the satellite, so positioning the antenna on top of the aircraft maximizes the satellites that can be seen and minimizes multipathing, and also gives some protection ...
- 2,679
7
votes
Accepted
What is this "stick" on top of Cessna 152's wing, and how does it work?
Short answer: They're antenna(s) for the onboard VHF radio(s).
Airplanes aren't actually required to have radios. But, if you want to fly into certain classes of airspace, you must have at least one ...
- 12.8k
6
votes
Accepted
Why does TCAS need 2 antennas?
Two antennas
As @Ron mentioned the fuselage is an opaque obstacle for waves, and two antennas are required to cover the whole space around the aircraft. The choice is to have one antenna at the bottom ...
- 76.6k
6
votes
Can you identify this antenna on a Cessna 172N?
Glideslope antennas are those U shaped stubby 3 prong fork things that look like heating elements for a water heater. That's a 75 Mhz Marker Beacon antenna. I have revised this post. I thought it ...
- 134k
6
votes
Why should the optimum position of GPS Antenna be close to aircraft's CG?
All GPS signals are line of sight and most receivers use all
satellites that are visible and a minimum of 9 - 12 degrees above
the horizon. So being on the top of the aircraft near the centerline
is ...
- 20.1k
6
votes
What are the radio characteristics of communications between tower and aircraft?
They are omni-directional: Anyone, in any direction, can hear the broadcast.
They are analog (non-digital), AM signals, so there are no bits, and thinking in terms of kbps or data-rate doesn't make ...
- 30.8k
5
votes
Accepted
AWACS - what do these antennas do?
The image below labels each of the antennas. To summarize based on your groupings:
A: Multi-Role Electronically Scanned Array (MESA) made by Northrup Grumman. It has a similar role to the large ...
- 73.5k
5
votes
Accepted
What are the radio characteristics of communications between tower and aircraft?
What type of antennas are used today for tower-aircraft comms? Are they directional or omni-directional?
The antennas are omni-directional however on the aircraft the mounting is important to ...
- 102k
3
votes
Why do planes use wire HF antennas instead of smaller ones used by airliners?
The antenna length is purely a function of frequency. In other words it is a function of the radio systems that were prevalent when the aircraft entered service, and not specifically the age of the ...
- 3,818
3
votes
Accepted
Why and how can TCAS and SSR transponder work at the received frequency of each other?
To clarify:
A transponder replies on 1090 MHz to ATC interrogations received on 1030 MHz.
A TCAS elicits nearby transponders replies by sending interrogations on 1030 MHz, and listens for replies on ...
- 76.6k
3
votes
Accepted
What is that wire connecting
It is an HF (High Frequency) antenna. It is used for aircraft to communicate on overseas flights. VHF (Very High Frequency) airband radios are used for normal local and cross country flights.
For a ...
- 16.6k
3
votes
Accepted
What are the names of the antennas which I have marked in this picture of a Boeing 737?
ATC, Altimeter Transmitters and Receivers, and DME-1
- 4,877
2
votes
How the Log Periodic Dipole Antenna of Localiser help in varying modulation depth?
Mod Depth (more commonly called modulation index in electrical engineering) is the amount a carrier signal is modulated. Mod depth has nothing to do with antenna configuration and is set by the ...
- 5,829
2
votes
What are the radio characteristics of communications between tower and aircraft?
It would seem the ATC outputs pretty low power!
This is from a General Dynamics Air Traffic Control radio data sheet
RF Output Power:
Low Power Transmitter 2-12 Watts with co-site filter,
2-20 ...
- 8,795
2
votes
How much extra drag does an external HF antenna incur?
As this film shows with brilliant simpliciy, the drag of a round wire is almost 10 times the drag of the same thickness streamlined shape.
Biplanes use streamline rod for flying and landing wires ...
- 134k
2
votes
Why did this old Japan Nakajima J1N airplane use a Yagi rather than a parabolic antenna?
Note that the assertion "It can only receive signal if the transmitting antenna is not exactly in front of it" is wrong. The most sensitive direction for receiving is in fact exactly in front of the ...
- 22.1k
2
votes
What is that wire connecting
It’s a high-frequency antenna, used mostly on flights traveling across seas and oceans, where there tends to be areas without VHF and UHF coverage. This was the case on older aircraft, most newer ones ...
2
votes
Accepted
Could a Cessna Caravan be outfitted with Wi-Fi?
Bendix King offers a TSO'd Inmarsat internet transceiver for the Caravan called an AeroWave 100, so the shortest answer is "yes." It's not inexpensive, you're looking at an installation ...
- 3,818
2
votes
Why should the optimum position of GPS Antenna be close to aircraft's CG?
Specific to question 2, that has not been addressed in other answers… The GPS MMR antennae receive GPS augmentation signals. In the case of WAAS, which is provided by stationary satellites, (SBAS), ...
- 3,818
2
votes
What type of antenna is this?
Its a comm antenna, Belly mounted antenna have a few purposes
Worth mentioning is properly planning the antenna placement for modern
audio panels, especially if you are installing antennas before you ...
- 102k
1
vote
What type of antenna is this?
Note: I'm not exactly an expert in this, so it's possible I've made some mistakes. I'm sure someone in the comments will correct me if that's the case.
#1: As the other answer says, this is the ...
- 12.8k
1
vote
What is that round antenna(?) on the bottom of a Piper Comanche?
That is probably the ADF loop antenna. To read properly, it must be installed so the little airplane's nose points in the direction of flight.
- 22.1k
1
vote
Accepted
Why did this old Japan Nakajima J1N airplane use a Yagi rather than a parabolic antenna?
First, both parabolic & Yagi antennas are "directional" in that their main lobe is designed to have high gain in a limited direction. this is because all antennas have to trade the width of their ...
- 1,932
1
vote
Is this a type of navigation aid?
If you go to www.skyvector.com and zoom in to MRB
(easy to enter a flight from KOKV to KMRB to find it quick)
Select the World VFR view, and you will see no navaids at that location.
Select the ...
- 8,795
Only top scored, non community-wiki answers of a minimum length are eligible