Antennae on a Cessna 172?
Kevin J. Edwards
Can anyone point me to an illustration that describes all the various
antennae on a Cessna 172? It's not in the POH and I want to make sure I can
correctly identify them for my oral exam.
Many thanks,
kevineAFR...@cnet.com
Please remove AFRAIDOFSPAM to send me email.
Jim Weir
shared these priceless pearls of wisdom:
->Hi,
->
->Can anyone point me to an illustration that describes all the various
->antennae on a Cessna 172? It's not in the POH and I want to make sure I can
->correctly identify them for my oral exam.
No illustration, but if you will guess me the year of the 172, I'll guess you
the various antennas and their locations.
Jim
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com j...@rst-engr.com
d...@stanwyck.com
> ...
> The 172 I fly has 5 on top and 5 on the bottom. The top ones are all wire like
> and the bottom ones are mostly fin like.
>
> First the top: The two comm antennae are on top adjacent to the wings. They
> are somewhat fat looking and they angle back. Half of the ADF antennae is
> strung between the top of the cabin and the tail (no, that wire isn't there to
> hold the tail on :-) ). The two VOR antennae are in a V-shape on the top of the
> tail (remember V-shape is VOR). The ELT antennae is a thin wire sticking out
> the empennage just behind the cabin.
>
> Underneath the plane is a little harder for me. I may need some help here. The
> other half of the ADF is down there as is the GPS. The other three are for the
> DME, and two other things (perhaps a transponder or two or the localizer?). The
> glideslope antennae is inside the cabin at visor level in the middle of the
> windshield.
>
> Did I miss any?
>
> Kristi
Let me add two more that my airplane (172) has:
On the top, centered over the passenger compartment, is a white "bubble".
That is the GPS antenna. (Kristi says hers is underneath, but that doesn't make
a lot of sense; satellites are, in the normal configuration, above the airplane,
not below it, so it better not to use the metallic airplane frame to shield the
antenna.)
On the top, half way back along the empannage (near the ELT antenna) is
something that looks like a car's FM antenna. That is for the avionics-grade
FM/CD player.
Don
Craig Prouse
kev...@cnet.com wrote on 11/29/00 1:28 PM:
> Can anyone point me to an illustration that describes all the various
> antennae on a Cessna 172? It's not in the POH and I want to make sure I can
> correctly identify them for my oral exam.
It really depends on what avionics are in the airplane and the discretion of
the avionics installer. There are also some variations in the design of
different antennae used in identical applications.
It's good to understand why antennae are not all the same; form follows
function. Specifically, antennae have characteristic geometries which are
optimized for the frequency range and in some cases the polarization of the
signals they detect. High frequencies are detectable with small antennae
while low frequencies may require antennae which are quite large. Where the
antennae are placed is also signficant based on the location of the
transmitter.
The GPS signals are extremely high frequency (in the range of a few GHz), so
the antenna is relatively small. The satellites are in the sky so the
antenna goes on top of the plane. It's usually a little wedge about half
the size of a hockey puck.
UHF signal sources include your transponder, glideslope receiver, and DME.
UHF signals also require relatively small antennae, and as these
applications are related to ground transmitters, you'll usually find them on
the aircraft belly. Often they look like shark fins. It may be difficult
to distinguish between a transponder and a DME antenna, but if they're both
present they're often physically separated to avoid interference between the
two. Glideslope antennae are sometimes located in the windscreen, but some
people have had problems with glideslope reliability due to interference
from the propeller at certain RPMs, so I don't think that arrangement is all
so common any more, at least in new installations.
VHF signal sources are your VOR, COM, and ELT antennae. As someone else
mentioned, the VOR antennae are often arranged in a "V" pattern on the
vertical stabilizer, which makes them easy to remember. The COM antennae
are usually right on top, and the ELT antennae is usually near the ELT
somewhere on the empennage. You'll notice that these are all about a foot
and a half long, characteristic of the 108-136 MHz VHF aviation band.
The lowest frequencies you receive are with your ADF, marker beacon
receiver, and perhaps LORAN. Low frequencies, big antennae (generally).
The long wire, if you see one, is usually for the ADF, although more compact
ADF antennae are now possible. Aircraft equipped for long flights out of
VHF range need HF radios, which also require quite substantial antennae.
Craig
Kristi9876
I don't have an illustration but I made a little study of it after I got
quizzed on it on my instrument checkride.
The 172 I fly has 5 on top and 5 on the bottom. The top ones are all wire like
and the bottom ones are mostly fin like.
First the top: The two comm antennae are on top adjacent to the wings. They
are somewhat fat looking and they angle back. Half of the ADF antennae is
strung between the top of the cabin and the tail (no, that wire isn't there to
hold the tail on :-) ). The two VOR antennae are in a V-shape on the top of the
tail (remember V-shape is VOR). The ELT antennae is a thin wire sticking out
the empennage just behind the cabin.
Underneath the plane is a little harder for me. I may need some help here. The
other half of the ADF is down there as is the GPS. The other three are for the
DME, and two other things (perhaps a transponder or two or the localizer?). The
glideslope antennae is inside the cabin at visor level in the middle of the
windshield.
Did I miss any?
Kristi
>Hi,
>
>Can anyone point me to an illustration that describes all the various
>antennae on a Cessna 172? It's not in the POH and I want to make sure I
>can
>correctly identify them for my oral exam.
>
>Many thanks,
>
>kevin
jga...@hotmail.com
"Kevin J. Edwards" <kev...@cnet.com> wrote:
> Hi,
>
> Can anyone point me to an illustration that describes all the various
> antennae on a Cessna 172? It's not in the POH and I want to make sure
I can
> correctly identify them for my oral exam.
>
You should have your instructor go over them with you. There may be a
standard position for various antennae on a brand new 172, but the older
ones have probably had antennas added and deleted from a dozen
locations (OK, maybe half a dozen). Once your instructor has shown you
what the various types of antennae look like, you'll be able to identify
them on any plane.
John Galban=====>N4BQ (PA28-180)
Sent via Deja.com http://www.deja.com/
Before you buy.
Kristi9876
Thanks for the GPS info. Duh, that makes sense. I'll have to look more
carefully tomorrow when I see the plane again.
Phillip Smith
locations around the aircraft depending on what radios, NAVAIDS etc are
installed??
-Phil
Kevin J. Edwards <kev...@cnet.com> wrote in message
news:B64AB4FD.1D79%kev...@cnet.com...
> Hi,
>
> Can anyone point me to an illustration that describes all the various
> antennae on a Cessna 172? It's not in the POH and I want to make sure I
can
> correctly identify them for my oral exam.
>
John Fincher
shaped antennae on the tail.
I'm sure someone will be sure to point out my mistake if I'm wrong!
John
krist...@aol.com (Kristi9876) wrote in
<20001129200146...@ng-mi1.aol.com>:
Troy Whistman
has a diagram of the antenna locations on the new Cessna 172R's. They do
have standard positioning. I wonder if I can scan and post one photo
without getting in trouble...
Troy
do...@tiac.net
is a loran ant.
I know the "long thin" wire that Kristi mentioned was the adf. I
wasn't sure there were two?
Also, one thing to watch for is out near the nose of the plane
sticking out the bottom...it may be one for your transponder.....
Don Paquette
T H
search for antenna. There is an article that describes most common
antennas. Kristi, what you think is the GPS under the airplane is probably
the ADF.
Tyson
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Simon Hewison
<krist...@aol.com> writes
>Underneath the plane is a little harder for me. I may need some help here. The
>other half of the ADF is down there as is the GPS. The other three are for the
If the GPS antenna is on the underside of the aircraft, it would
surprise me; GPS works best with line of sight to as many satellites as
it can see. This normally means the satellites are above the aircraft.
I haven't flown a 172, but on every GPS equipped aircraft I've flown,
the GPS antenna was on the top of the aircraft, normally with helpful
writing on it like "GPS Antenna. Do not paint".
--
Simon Hewison
Mark Kolber
<kev...@cnet.com> wrote:
>
>Can anyone point me to an illustration that describes all the various
>antennae on a Cessna 172? It's not in the POH and I want to make sure I can
>correctly identify them for my oral exam.
Couple of years ago, Flight Training did an article on antennas. I
have it in PDF format. Email me if you're interested.
Mark Kolber
Denver, Colorado
========================================
email? Replace "spamaway" with "mkolber"
Russell Kent
alike, since many have had avionics added or removed over the years. For
example on the 172 I fly, there's one antennae I cannot identify and my
instructor cannot tell me much about. It was added for a classified (read: DOD)
project that the aircraft participated in a number of years ago. The aircraft
belongs to the Texas Instruments flying club, which had an arrangement with part
of the company a few years back...
So if asked about it, I'd tell the DE that *that* antennae is not connected to
any equipment currently in the aircraft, and I do not know what purpose it
serves.
Russell Kent
"Kevin J. Edwards" wrote:
> Hi,
>
> Can anyone point me to an illustration that describes all the various
> antennae on a Cessna 172? It's not in the POH and I want to make sure I can
> correctly identify them for my oral exam.
>
tjwit...@my-deja.com
two feet long mounted below the fuselage and parallel to the
longitudinal axis of the aircraft.
jga...@hotmail.com
r-k...@ti.com wrote:
>For
> example on the 172 I fly, there's one antennae I cannot identify and
my
> instructor cannot tell me much about. It was added for a classified
(read: DOD)
> project that the aircraft participated in a number of years ago.
<snip>
>
> So if asked about it, I'd tell the DE that *that* antennae is not
connected to
> any equipment currently in the aircraft, and I do not know what
purpose it
> serves.
Or, you tell the DE that the antenna is part of a classified DOD
project. You can tell him what it's for, but then you'll have to kill
him :-)
John Galban=====>N4BQ (PA28-180)
Jim Weir
shared these priceless pearls of wisdom:
->Only mentioned once was the marker beacon antenna. Mine is a rod about
->two feet long mounted below the fuselage and parallel to the
->longitudinal axis of the aircraft.
Two kinds of common marker antenna. One is the "rod" (called a "sled") about
39" long and bent into the shape of a J. On the short leg of the J the antenna
is grounded to the airframe. About 8" aft of the ground there is a through-skin
insulator that attaches a wire from the coax lead-in to the rod about 10" down
along the rod with a metal clamp.
The other marker antenna looks like the upside-down cover from a butter dish,
and it is called a "boat".
Andrew Gideon
jga...@hotmail.com writes:
> In article <3A2D7E41...@titania.tye.sc.ti.com>,
> r-k...@ti.com wrote:
>
>
> Or, you tell the DE that the antenna is part of a classified DOD
> project. You can tell him what it's for, but then you'll have to kill
> him :-)
>
Antenna? I don't see any antenna there, and you'd best
not either.
- Andrew