GeorgeF wrote:

In my last post I used the term NAV and COM. Let me clearify what they
really are. An aircraft (anything from a 4 seat Cessna to a Boeing 747,
it doesn't matter the radios are just about the same) generally has 2
NAV/COM radios. Each NAV/COM is in reality 2 radios in one box, the
NAV side and the COM side. The NAV side, which stands for Navigation is
a receiver only and will receive VOR (naviational radio beacons) signals
from 107-118 MHz. The COM side, which stands for Communication is a
transceiver used for talking to ATC (Air Traffic Control), FSS (Flight
Service Station), or other aircraft. This radio will tune 118-136 MHz.

If you look at this pictu http://www.wingsonline.com/sterubp.jpg
you'll see part of a Cessna instrument panal. On the right side
starting at the top you'll see a box with lots of little buttons. This
is the audio/mike panel. It controls the where the audio from all the
radios goes, you can have one or all radios going to the overhead
speaker or to headphones. It also controls which transceiver your mike
would be connected to. In reality most small 4 seat planes can have up
to 9 radios:
COM-1 for communications
COM-2 for communications
NAV-1 for VOR, ILS (instrument landing system) navigation
NAV-2 for VOR navigation
ADF Automatic Direction Finder (usually tunes 200 KHz to 1600 KHz)
DME Distance Measuring Equipment, using radio wave to measure distant to
a VORTAC
MBR - Marker Beacon Receiver, used as part of the ILS system
TRANSPORDER - Send's code and altitute to ATC's radar screen
ELT - Emergency Locator Transmitter (transmits on 121.5 & 243.0 MHz)

And today many small planes have GPS so that would be the 10th radio on
board....

In the picture I refered to above if you look under the audio panal
you'll see two NAV/COMs, since they're turned off they just look like 4
independent radios and in reality that is what they are.

Hope you enjoy the "Aircraft Radios-101" course...There will be a quiz
later...

George
http://www.MilAirComms.com