A guide to receive far away FM stations

[mundle2002]

For the FM band with the centre frequency of 98 MHz, we have to first calculate the wavelength by the formula:-wavelength(in meter) = speed of light(m/s) divided by frequency (in Hz).therefore, wavelength = 300000000 m/s divided by 98000000 Hz. = 3.06 meters.The length of the antenna should be some multiple of the wavelength. This is because the antenna must present itself as a resonant circuit to the RF signal so as to maximize the power in the antenna.It can be either 1/4th wavelength = 75cm as those used in Radios.It can be 1/2 wavelength = 1.5m (a dipole)or a full wavelength.You can download the pdf of the article "Mosfet based amplifier for FM radio DXing" from the website of "Electronics for you" magazine.Although i used the antenna design from the article, i didnt use the circuit.I used the circuit from the article "FM booster". You can also get the same circuit from the website You can also design a Yagi antenna:-Length of dipole = 1.5m.Length of reflector = approx. 5% larger than dipole.Space between dipole and reflector = 0.2*wavelength.Length of 1st director = approx. 4% smaller than dipole.Space between dipole and 1st director = 0.12*wavelength.Make the 2nd director by decreasing 4% length as compared to 1st director,make 3rd director by decreasing 4% length of 2nd director............and so on.................you can add as many directors as you like.The inter-director spacing will be 0.12*wavelength.Although the Yagi antenna is a little bit bulkier and prone to breakage by the birds sitting on it, it will definitely give a greater gain compared to any other antenna.

 

[raja_meghana]

Thank you delhilama. Very useful links.

 

[jishnu1980]

hello iam also new to this forumiam from kerala 4 private fm stations near to us (around 25 kms road distance(not air distance if it calculated only 15 or 16 through air) all the 4 players said that their signels cover 50 kms from the point of transmission but we dont get it clear inside our home using Sony home radio (in some rooms not even signals) but its clear in car audio using full length antenna this problem facing allmost all the peoples near to me any suggestion to get the signals inside the room clearly

 

[ItsMe]

@jishnu1980, This is a problem when you live in an area where there are lot of trees and other obstructions. You should be able to receive all channels clearly if you try tuning outside your house. The easiest and the cheapest solution is to go for an external antenna and a small FM booster. try checking with your local electronics shop.

 

[rishabh sethi]

fm where i will get a fm booster aand what will be its cost and a signal booster or fm booster which one

 

[raja_meghana]

Probably you could try coaxial cable used for TV antennas as an outdoor antenna before going for any signal boosters. The following is a link to one such design. It is very very simple to construct and very cost effective. You can use a small piece of wood to support and keep it straight horizontally. In fact I made one to receive fm transmission which is aired via 1 kw transmitter from a distance of 30 km. here is the link.

Make your FM Dipole antenna by dxzone.com

Link for simple fm loop you can try for better reception

Simple FM Loop

to order a mosfet-based fm signal booster circuit and components from elecronicsforu website, but you have to have some knowledge in electronics to assemble it.

Circuit lab, diagrams,Free circuits, Electronics periodical, e-mags: India

 

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[jim]

Hi everybody,
After reading the previous posts, i thought to share something which might be unknown to some people. Receiving far away FM stations is called FM Dxing. I am from Ranchi(Jharkhand) and unfortunately here we dont have private FM stations except Vivid Bharti:wall: . But i do listen to FM stations of Kolkata(Calcutta).
I want to make it clear to everybody that high frequency signals travel in the line of sight and these high frequency signals can either be FM or AM.
So, saying that FM signals travel in the line of sight is partially correct.
Low frequency signals like MW and SW also travel in the line of sight but they also get reflected by the one of the layers of atmosphere. So we can listen to faraway stations in these bands.
High frequency signals do not get reflected rather they pierce the layers of atmosphere and are lost in space leaving only one option: line of sight transmission.
But there is a special layer in the atmosphere called ionosphere which helps in reflecting the high frequency signals. Although not always present, this layer is responsible for FM Dxing.
To receive distant signals you need:
1) A good FM receiver. (I have got my Sony home theatre which works very well)
2) An FM Booster(Not those TV boosters)
3) A home made antenna.
You can get a plenty of circuits diagrams in the internet for FM booster.
Print out the diagram and either make it yourself or give it to the technicians who repair TV and radio.
The antenna can be a simple one like a whip antenna if you want to listen to nearer stations or it can be a complicated one like Yagi antenna. I made a quadrangular antenna.
With the help of above things, i receive FM stations of Calcutta. In a straight line it is more than 350 Kms from Ranchi. The signals become clearer in the night and they become stereo from mono.
Thus my setup receives whatever signals it gets from line of sight and from ionosphere reflections.
Some other facts:-
Aircraft communications also use high frequencies (118-136Mhz) and they talk in line of sight BUT THEY ARE NOT FM, they are AM (amplitude modulated) signals like those of Medium wave and Short wave.
One interesting thing:- One day when i switched on my system i wasnt able to receive Kolkata FM stations rather i was receiving radio stations of Burma(Myanmar) . I took out the map and measured the distance of Burma. It was more than 1500 Kms. Isnt that interesting:yahoo:May be due to changes in the ionosphere i was able to receive them.
It might seem surprising to you that i am a Doctor but electronics and communication is my hobby. I hope you enjoyed reading my little article. Need any help?

Sir,
I really enjoyed ur article. I am a civil engineer with ur same interest. I am from kerala where FM stations are not available. Now many new private stations started which are 110km to 170km away. Ur article inspires me for FM Dxing. I have down loaded an FM booster circuit. Now I would like to know the details of an home made antenna (quadrangular). If u don't mind pls giv me the details to construct it.
with regds,
jijimon
email : [email protected]

 

[mcx]

Hai everybody, I am also a radio enthusiast living in kerala,(near kottayam in kerala) this place is not in the primary coverage of any fm transmitter so without doing anything it was difficult listen to fm here ,really :and so I was using external yagi antenna for the last 8 years . Really like to listen to and share anything related to FM radio particularly fm dxing.it was my hobby since childhod I would like to thank mundle 2002 and others for thier posts in the forum which i found so interesting. I would like to ask one thing : the impedance of yagi is 300 ohm right,so what cable would u guys recommend to connect a 300 ohm ribbon cable or 75 ohm coax ? Or adding directors to decrase the impedance to connect a coax? but will it become 75 ohm? .or these impedence mismatch really doesn't really matter? but whenever I use long cables the signals received at the antenna die out as thay come down which made me use an old tv VHF booster 300 ohm which is not optimised for fm amplification .I couldnt build an fm amp myself to satisfaction yet because i am not a professional in these things (,actually i'm a junior doctor trying for pg entrance )so still using the old one.these things are not available in the local shops here. Any how hail the fm revolution in kerala ! Expecting replies with regards mcx

 

[jishnu1980]

hello jim and mcx iam also from kerala intrested in radio i wish to make friendship with u guys iam also a professional if intrested contact me on mail [email protected]

 

[mcx]

Hai Jishnu, great to have u as friend. Its good that we have a common interest in radios. U see the problem was that I couldnt talk to my friends about these things or ask them any doubt here as they were least bothered about fm radio.everyone is in front of the satelite tv or dvd or seeiing streaming video/audios from the internet so i never had an outlet to speak or share my apparently rare hobby.Its good that i get an opurtunity here like to listen to radio at home as a background audio and in car.But unless we get a hazzle free reception in mobile phones or inexpensive radio sets here the general public will not have a likeness for it especially in my place. It seems with the coming of new private stations radio is back and generating lots of interest at least in the major cities in kerala.But I think people from other states are better listeners than malayalees.When in big metros I found that alsmost every young person in the bus, train in the park,....seems to be enjoying,listening to radio stations in their mobiles and also in taxis ,autorickshaws ,everywhere fm stations had a better reach than tv in the city because they where available on the move.they dont have to buy cds or download music off the internet as new songs where played in the radio with near cd quality. My problem with reception is that the power of signals are fluctuating.in day time big 92.7 and radio mirchi from trivandrum, i get crystal clear stereo reception which will die out comletely ,in 1 or 2 minutes it becomes clear again in another minute this continues all the day.In the night it is good.I'm desperately trying to increase the gain.any suggetions?