so I read in my other post that you can tweak and fm radio to receive civil aircraft frequencies. so hows it done? like with the coil? and would a normal fm radio pick those signals up?

 

see, you can easily tweak a basic fm radio to receive civil aricraft frequencies . now what i mean by basic is an FM radio without synthesiser tuning.like the ones which you can tune with a variable capacitor.

now heres how....

locate the antenna tuning coil. one easy method is to tune the radio onto some station and then bring a metallic screwdriver near the coil. if the radio drifts and the station does not come in clearly, u hit it.....thats the main tuning coil.

now stretch out that coil slightly. when the coil turns are more apart, its inductance is less. so ur tuning range increases.

now you will see a few IF transformers. one of them is to prevent AM noise from getting into the reception.

now aircraft transmissions are in AM so AM noise is exactly what u need.

take a plastic screwdriver and turn the core of the IF transformer slowly until you hear quite a lot of noise comin in.....its kind of finished now

take it near an airport and try tuning in....when i mean near, i mean a few km....tryin to get into the airport with a thing like this will get u arrested!!

even if you are not very near an airport, you can hear transmissions from aircraft flying by..

cheers

 

so i can hear them from my house lets say? just the aircraft flying over? or i take it outside and i can hear the aircraft flying over me but not close to an airport?

 

yes....if u take it to ur terrace u can definitely hear the aircraft transmissions. and if ur close to an airport, u can hear the control tower too.....

 

well how do i find the IF transformer? theres like 5 also i expanded the coil to what i think is 124 mhz because i tuned it until i heard music that is on approx 108 mhx then i started turning it and t stopped turning to the left at 104 mhz so from 88 thats 16 added to 108 so 124. now i in the background on the freq higher than 108 mhz i hear the AM stations coming in very faintly. also i hear no aircraft

 

Civil aircraft use 108MHz to 135MHz

 

Actually, 108 to 117.975 are Navigation beacons, like Vhf Omni Ranges, Instrument landing systems, Localizers, etc. Not much voice modulation. Normal voice communications occurs between 118 and 137 MHz.

The reason that a wide-band FM receiver is not suitable to be used to receive AM broadcasts is because the FM receiver is specifically designed to eliminate any amplidude modulation on any signal that it hears.

Trying to diddle an FM receiver so that it tunes the Aircraft Band is a really bad idea; It will ruin the FM receiver, and never work well as a useable aircraft receiver.

Get an old programmable scanner which includes the AM aircraft band. I have one that receives high-flying IFR aircraft out to a distance of 250mi. It receives radio traffic from several local airports.

To learn what frequencies are used at your local airport, go to AirNav and put in your city.

__________________
Mike ML.

 

yes mike,....fiddling with an FM radio will not give u a performance comparable to a dedicated aircraft scanner, what we are discussing here is how you can modify an fm radio for two things....one ...its cheap,...and its fun....you can learn a lot ...which you can never get if you buy it off the shelf..

cheers

 

polish dude....heres how you can find which is the correct IF transformer you can tweak...slightly turn each of them a few degrees....if you hit the correct one....you can start hearing a lot of background noise and hum....thats the correct IF tranny...

as mike said....it will not be as good as a dedicated airband receiver but you can definitely hear aircraft close by.....after you manage to tweak it to the correct tuning range....you will definitely hear stuff...one way to know if you are on the correct frequency range is to listen for the ATIS transmissions.....(automatic terminal information system)...this is an automated audio message which keeps repeating informing the pilot the local whether conditions...and other important details such as which is the main runway etc.....

the other frequencies will be close by...

 

A few items that might be of interest:

In several of the ARRL Radio Amateur's Handbooks is a relatively simpe aircraft band receiver project. Just like the modified FM radio, you cannot expect high levels of performance but it is likely to be a good learning experience.

Worth noting are the shortwave frequencies used for long distances where VHF just doesn't provide the range. There might be 4 or 5 active channels on several bands - the choice of band being dependent on time of day and propagation.

__________________
stevez

 

thank you very much stevez....

 

polishdude.....plz tell us if you have successively managed to modify ur fm radio to receive aircraft frequencies..