Introduction: Airplane Radio (eavesdrop on Your Pilot)
In this instructable, I'll show you how to modify a normal, analog AM/FM (or FM) radio so that it can pick up the broadcasts from airplanes and airplane control towers.
First, a little background on how this works. Airplanes broadcast using AM. AM means Amplitude Modulation, for the uninitiated. They transmit from around 115 MHz to about 140 MHz; for comparison, the AM broadcasts that are normally picked up by a radio are from 530 KHz to 1705 KHz.
We will be converting the part of our radio that normally picks up FM to pick up AM in the airplane frequency band.
Step 1: Supplies
All you need for this (other than yourself and batteries) is:
1) A REALLY cheap analog FM or AM/FM radio. I picked up mine for $5.
2) A way of opening your radio without breaking it (usually a Phillip's head screwdriver)
3) A flathead screwdriver
Step 2: Crack It Open!
Open up your radio, most likely with the screwdriver (unless it just pops open from its cheapness).
Observe its parts.
Step 3: Convert It to AM
Notice a little silver box with a circle cut out on top and a colored circle recessed inside with a line just perfect to fit a flathead screwdriver in? Well, we need to loosen it to allow us to pick up AM, and not filter out everything but FM. To do this, insert the flathead, and rotate counterclockwise about 5-10 times. Your radio may have a few more of these. Repeat the aforementioned step for all of them.
Step 4: Change the Fequency
You will notice a few coils in there. If your radio also picked up AM before it was modified, it will have a large ferrite coil. Ignore it. All we are focusing on is the few small coils. Spread them apart as much as possible, keeping them in a generally coily shape. It is easy to do this with your flathead screwdriver.
Step 5: Close It Up and Enjoy
Close up your radio--you are finished! Set it to receive FM (even though we know it will actually be receiving AM). You will be able to hear broadcasts from aircraft from where the dial says about 700 MHz and up. Below that, you will hear some normal broadcasts. Go outside for somewhat better quality, and when you are close to an airport, you will be able to hear the ATIS.
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32 Comments
6 years ago
Were do you guys get your frequencies, that is not at all accurate. Airplane frequencies are 110-200 MHZ depending on the airplane. a Mode 3 6760 (jetliner) will be on a center frequency of 190-199.
New York Center (Hartford, CT, yeah New York center is in Connecticut go figure) ZNY is actually 199.75,
KEWR Airside (Newark Liberty, Elizabeth, NJ) is 199.25.
KLGA Airside (LaGuardia, New York City) is 199.30.
KIDL Airside (John F. Kennedy, New York City yes its call letters are KIDL despite what everyone thinks its original name is Idlewild) is 199.65.
Taxi Control frequencies at all airports are 150.25 in New York Area
Control Frequencies of Washington Center ZDC (Baltimore Washington Area, Silver Springs, MD) 196.75
KPHL Airside (Philadephia, in Easton PA) is 192.50
KBWI Airside (Baltimore Washington in Jessup, MD) is 194.20
KACY Airside (Atlantic City, in Pleasanville, NJ) is 193.80
FAA Flight Research Center in Pomona, NJ is 198.25
Crisis Management Frequencies.
Star Alliance, United Continental, USAir, America West 150.90
Not sure what Delta or any other is don't usually deal with them.
Reply 6 years ago
Uncontrolled Airports are on 122.50, 121.50 is also the civilian distress frequency chances are if you are wanting to hear your pilots you are in a Mode 3 6760 plane,
Mode 3 6760 planes basically a civilian plane with jet engines
Mode 3 5560 planes basically a civillian plane with prop engines 2 or more engines with the exception of sea and bush planes.
All civilian planes must squawk a mode 3 code which says they are a passenger or cargo plane and are friendly,
A mode 1 plane is a fighter jet,
A mode 2 is a military cargo get
A mode 4 is a military troop transporter
A mode 5 is a special ferry flight
8 years ago on Introduction
Nice to see the old-school hacks being revived. This 'mod' most definitely works. I performed this modification to a transistor radio of mine back in the 1970's when I was just a kid. I learned how to do it from reading Popular Communications magazine back in the day. The challenge is that the dial no longer represents the 'new' frequency receiving range of the radio and you just have to keep scanning the airwaves by moving the tuning dial back and forth until you pickup a signal. When you do, make a note of it, mark it on the radio dial. Odds are you only have a few specific frequencies allocated to the air band in your area that you can receive signals on anyway. So mark them, then just set it and listen in....enjoy.
73
10 years ago on Introduction
Nice instructable by the way, i will give it a try & let u know what i come up with!
10 years ago on Introduction
I have an idea, for all of those saying it doesn't, shouldn't, or won't work... just try it... :) then have ur say
11 years ago on Introduction
I forgot to mention the red can is always the am osc coil.what the whole thing is about is detuning everything ,no selectivity ,anything strong around that frequency will be received. you might get a better reception if you build a crystal set at that freq with a high gain audio amp.
11 years ago on Step 3
Thats the am local oscillator coil you are playing with,got nothing to do with the FM. these days you will not find any cans for the 10.7 IF. wide bandwidth resonators are in place. here in oz the am bandwidth is 9kc's.I would love to see how these mods cater for front end traking.the only way one will hear anything if very close to the tx.
13 years ago on Introduction
No.
You cannot convert an FM receiver to AM by twiddling these things. There is a fundamental difference between the signal modulation, which you ought to understand.
L
Reply 13 years ago on Introduction
The antenna/receiver size requirement would also be a dead giveaway against such a switch.
Reply 13 years ago on Introduction
Everyone keeps thinking this won't work. It DOES!!! Would someone please ask for a type of evidence instead of instantly and blindly bashing it? And yes, the antenna size is small, which is why it doesn't pick up airplanes as far as is normal, but it certainly works. JUST ASK FOR EVIDENCE. I WILL GVE IT TO YOU! I live nearish to a small airport; would a video with sound taken in front of it convince you?
Reply 13 years ago on Introduction
electrick
This is an open forum system - please try to keep in mind that most of us are not "instantly and blindly bashing" your idea, but are instead trying to figure out how such a system would work lacking any evidence or supporting schematics/theory. If you want people to instantly believe you, maybe you should try providing said evidence at the outset. pkander below described a series of circumstances that may allow me to believe in this modification - I still need to read up on it, having some doubts - but you have proven no understanding yourself. Provide some designated information before bashing instructables members for trying to learn what your system does.
Reply 12 years ago on Introduction
Actually, it is kinda blindly bashing it. You havn't givenwhy it doesn't work, just that it "doesn't".
Reply 13 years ago on Introduction
There is a fundamental difference between the signal modulation in AM vs FM, you can't change that by tweaking a couple of things.
L
Reply 13 years ago on Introduction
lemonie,
If you are having a hard time getting your head around this instructable, then you should learn about slope detection where an AM radio can hear the sound of an FM transmission WITHOUT ANY MODIFICATION.
Go to wikipedia here, http://en.wikipedia.org/wiki/Detector_(radio) or the Electrical Engineering Training Series here, http://www.tpub.com/content/neets/14184/css/14184_163.htm, to learn how it is done. Or just google "slope detector".
Electronic circuits do not always operate as intended, especially analog circuitry. Did you ever hear a police call on a TV? Have you heard a local radio station's audio when the input cable to your stereo amplifier was loose? How about computer code that runs amuck? Things respond in ways that they were designed to do. Regardless of theory, there is much trial and error to get it right. A design compromise can bite you in the butt when you least expect it. Saying it isn't so or it shouldn't be does not change reality.
Reply 13 years ago on Introduction
It says Set it to receive FM (even though we know it will actually be receiving AM). The wiki link you posted says of slope detection: an AM radio may detect the sound of an FM broadcast and the other one refers to picking up FM signals also. That isn't the same thing is it?
I can quite easily see how the receiving frequency range may be shifted, and I don't doubt that it works.
L
Reply 13 years ago on Introduction
It WILL work, but quite compromised.
FM (frequency modulation) broadcast band IF bandwidth is typically around 75khz or so centered around 10.7 mhz. The FM IF amplifier is a limiting amp - it is designed to saturate thereby obscuring most amplitude modulation and the discriminator is tuned to be sensitive to variations in frequency, not amplitude.
Aircraft band AM (amplitude modulation) IF bandwidth is more like 5khz usually centered around 455khz, the IF amp is linear and the detector responds to amplitude variations.
In step 3, turning the slug 5 or 10 turns severely detunes the FM discriminator making it susceptible to amplitude variations, hence detecting AM.
In Step 4, the local oscillator frequency is increased by stretching the LO coil thus raising the frequency around 30mhz. Now the radio tunes ~120mhz - 140mhz instead of 88mhz - 108mhz.
The compromise is that the RF input is still tuned to the FM broadcast band, the IF strip is 15 times too wide, it limits so it will add distortion as well and the detuned discriminator is still a poor AM detector. All this leads to greatly reduced sensitivity but as the author says it can pick up close, strong signals.
Reply 13 years ago on Introduction
Thank you for corroborating!
12 years ago on Introduction
mine doesent have the transistor,can mine work?
12 years ago on Introduction
isnt this dangerous to the planes? it doesent interfiere with the normal radio contact right? we r just listening right?RIGHT?!
13 years ago on Introduction
did u actually test this thing?