Build Your Own Micro FM Broadcast Station

It all started when I was in the sixth grade. A science fair was coming up and each student was required to submit and present a project. I wanted my project to be different. So I started researching on our small library and ended up reading my favorite magazines: Boys Life, Popular Science and Popular Electronics.

One of the adds that caught up my attention was an FM Wireless Mic that can broadcast voices to distances of up to 2 kilometers. You could have seen the 1000 Watt bulb floating above my head. Right then it was no longer about the science fair. I don't care if I flunk it or not. I really got to have that fm transmitter.

The manual to build this fm transmitter costs $30. The company that sold it was Xandi Electronics. Now how was a sixth grader like me get a manual like that. The company was halfway around the globe... no internet, no email addresses, no paypal...

I once sent a letter to the White House asking if their were ghosts roaming the hallways. The president that time was Ronald Reagan. Well what do you know? I received a magazine and a letter from the White House. That inspired me to write a letter to Xandi Electronics. I told them if they can teach me how to build an Fm Transmitter like the one shown in Popular Electronics so that I can join the Science Fair.

DING!!! DING!!! Three months later I got the manual for the transmitter. It included an invoice with this simple words - "PAID IN FULL. GOOD LUCK WITH THE SCIENCE FAIR KID".

The rest is history... at an early age I learned how to fabricate my own circuit boards(etched) and assemble electronics kits from scratch.

My first true FM broadcast station was based on the BA1404 Stereo FM modulator and followed my own circuit design. I constructed it when I was in college and had a maximum output of 350mw with a range of 1 mile. It virtually turned our room into a mini FM station where we catered to song/greetings/announcement request from students.

I will be presenting three set-ups.

1. Basic Low Power FM Broadcasting Station (like the one I had in college)
2. Personal computer based FM Station (my preferred setup)
3. My dream Stereo FM Broadcast Station

But before anything else, we'll run through the basic building blocks of an FM broadcasting station.

BASIC BUILDING BLOCKS

A. FM Transmitter - this is the one responsible for getting you on air. It depends mainly on your budget, audience and desired range. E.G. You'd like to broadcast mini radio programs in your dormitory... then you'd probably just need a 350 mw to 1watt transmitter. This would be good enough for a range of up to 1 mile radius. the radio electronics involved are fairly simple but I cannot cover it on this lens. Hmmmm... another lens perhaps.

B. Antenna - the RF signal produced by the transmitter is channeled through an antenna and projected omni directionally (I guess that means all around). Antennas should ideally be located on the highest location possible. In dormitories, it is good to place it on the roof on top of a 20 foot pole. A mountain top would be a good place to put it. If you don't have a mountain then I guess you have to build one... hahahaha!!! Logic suggests that an good antenna is a better investment than a powerful amplifier.



C. Coaxial cable - before the RF signal goes to antenna it passes first through the coaxial cable. This also depends on your budget and transmitter. Luckily all our setups here are works great with the common RG-58 or RG-213 cables. A note of advice: keep your coaxial cable from the transmitter to the antenna as short as possible to minimize distortion and power loss.

D. Power supply - like your common electronic appliance, transmitters require a power source. It is good practice to have a regulated power supply for an FM transmitter. This reduces hums and other distortions making your fm broadcast clean and professional

E. Audio Equipment - a cd player would do. An ipod would be much better. But the best is a personal computer with Winamp. There are other audio equipment you might need, again depending on your budget. E.G audio mixer, microphones, headphones, telephones...

F. Radio Etiquette - don't expect everybody to like your show. In the long run you're bound to step on others toes... so minimize this by acting responsibly. Children could be listening. Keep it as G-Rated as possible like this lens.

This is my favorite FM transmitter. Pity it doesn't work with a laptop. They used to sell this in kit form and using ISA slots. They upgraded it to use the PCI slot. This is the most advance version of the transmitter.

Here's a description straight from the manufacturers:

"PCI MAX 2007+ is a computer card that will change the way you listen to your MP3's or other audio via PC. It will effectively change your PC into a stereo FM radio station, it is a small digital FM transmitter in a form of a PCI PC card. You will be able to play your audio files (CD, wav, MP3, real audio etc.) from your PC through radio waves directly to your household radio receiver in the next room, in the living room, across your yard, in whole block of flats....or for the entire village/small city. You need just an ordinary radio receiver to receive your signal. You can either service your living room, garden or an entire community. Get rid of those pesky cables!"

The wonderful thing about is that you have complete control of the fm transmitter through a special software and it can harness the power of your personal computer's audio setup. There are five on-board power setups for this fm card when purchasing: LPFM (100-350 mws), 500 mws, 1 watt, 2 watts and 2.5 watts.

I recommend power setups 1 watt and above. This recommendation takes into account the possibility of increasing the power in the future. Most fm power amplifiers require 1 watt of rf input.

PCI MAX 2007+ PC stereo FM transmitter card

If the power out put of the setup above(even if you choose the platinum version) is not enough for your needs, then this one will get you that extra coverage. This baby can generate a maximum of 15+ watts of raw power. The output quality can rival any commercial broadcasting fm station.

Read this short description:

"This package is based on the PCIMAX 3000+ PC based exciter card, but also comes with a 15W amplifier, coaxial cable, antenna and audio cables. This PC-based FM transmitter operates in the whole band II, from 87.5 to 108 MHz. This is a small, but well built and reliable package, with high quality transmitter and an optional RDS encoder. Output power can be adjusted from 0 to the max of 15W. This is a perfect backup transmitter for a large radio station, main transmitter for a small community radio, drive-in cinema, church radio or political campaign. Also very suitable for portable or improvised installations and small radio stations in Africa and other remote installations, for advertising (housing, shops), special occasions, wireless sound distribution, translation, tourism.... ."

I'd trade my laptop for a set up like this. I had the PCI Max 2004 but the output amplifier I used was assembled from a different schematic plan. It did work well but I never got past 10 watt barrier.

PC-based 15W transmitter package

What if you don't have laptop? That is not a problem. The FM Transmitter cards above have accessories that can convert it into a stand alone module. You'll have to shell out a few dollars (lots of few dollars) for some add-on components. The disadvantages would be is that you will now have a mobile FM station. I don't know with you but I prefer carrying a laptop than a desktop.

"PCI MAX 2007+ can also be used in stand alone mode! A small control unit with LCD display can be connected via flat cable and enables changing of the frequency, power and stereo mode. LCD and PCIMAX can be mounted in a convenient 19" 1H rack. Power jack for the card is already provided on the board, it requires 12-13.8V DC / 1A (center +). Put it in a box and you've got a stand-alone transmitter with high quality stereo encoder, balanced inputs (only pro units have this), optional RDS (similar to RDS MAX 4000+) and excellent sound. Add our 15W booster and you've got a nice 15W transmitter."

PCI MAX 2007+ accesories for STANDALONE operation

It has everything you need in one package. No messy assembly or installation. It works straight out of the box with all performance of a professional FM Station. Plug it in, attach it to your PC, attach the antenna, snap in a microphone, snap in a headphone, turn the power on, boot your computer... and you on the air.

"This package is based on our CYBER MAX FM+ 15W rack mounted FM transmitter series for demanding broadcasters, operating in the whole band II, from 87.5 to 108 MHz. This is a small, but well built and reliable package, with high quality transmitter (DSP stereo and RDS options), antenna, mains power supply, connectors and coaxial cable. This package can also be powered from a car battery (13.8V-15V), which can save lives in emergency. A perfect backup transmitter for a large radio station, main transmitter for a small community radio, church radio or an exciter for a larger 500W, 1KW, 2KW or even 250KW FM amplifier. Also very suitable for portable or improvised installations and small radio stations in Africa and other remote installations, advertising (housing, shops), special occasions, drive-in cinema wireless sound distribution, translation, tourism.... ."

ADVANTAGES
- Excellent audio quality (especially DSP model)
- Enough power for up to 15km of range or more with good antenna and location
- Fully portable and can run from car battery or battery pack.
- Includes everything, even coaxial cable and antenna.

DISADVANTAGES
Hardly any. Oh one thing... it could be the cure for your Squidoo addiction... yep a new addiction

The basic package comes in Mono. If you'd like it running you have to add an Stereo encoder.

My recommendation is to choose package B or package D. It will give you the best value for your money.

15W FM transmitter package

SE5000 DSP+ stereo encoder

These are the two characteristics that I always look for in FM broadcasting antennas: omnidirectional and no tuning required.

Omnidirectional means that your broadcast would be transmitted equally around you. This is very good when your in a dormitory or in a small city. No tuning means that you don't need to adjust anything when moving between fm frequencies.

I always designed my own antennas when I was in high school and college. Now, however, although I still recommend building your own antenna, it is much better to buy one. This way you can concentrate more on optimizing you mini FM station and programs. No more wasted time. Without further ado, I present to you preferred antennas to go with the setups I introduced above.

3-element YAGI antenna for low power FM transmitters

Precise manufacturing, low price and no-tune operation make this directional YAGI antenna (radiates most of the signal forward and back) a good match for low power transmitters such as PCI MAX 2007+. It is recommended where only small power will be used, funds are limited and there are no measuring instruments available for tuning. It also greatly enhances signal reception, if used in a receiver.While the antenna itself can handle considerable power, the ferrite balun used limits power handling to a couple of watts.


3-element YAGI antenna for low power FM transmitters


Single Circular Dipole for low power FM transmitters

Precise manufacturing, low price and no-tune operation make this omni-directional antenna a good match for low power transmitters such as PCI MAX 2007+. It is recommended where only small power will be used, funds are limited and there are no measuring instruments available for tuning. It also greatly enhances signal reception, if used in a receiver.

The uniquedesign helps deliver good signal to vertically and horizontally polarized receivers, ensuring better reception in all conditions. While the antenna itself can handle considerable power, the ferrite balun used limits power handling to a couple of watts.

Multiple antennas can be arranged in super-cheap multi-bay array, which also considerably increases power handling ability. An array of four dipoles can be used with our Cyber max FM 15W series transmitters and will provide incredible range at incredibly low price.


Single Circular Dipole for low power FM transmitters


Omnidirectional magnet-base mobile antenna with cable

Very convenient, with pre-installed coaxial cable and connector and its versatile magnet base. This omni-directional (radiates in all directions) antenna is a good match for low power transmitters, such as PCI MAX 2006+ or cyber max micro. It is recommended where mobile operation is preferred. Magnet-base is heavy and antenna stands by itself securely even when there is no metal underneath. Suitable for low power FM transmitters in mobile applications, for presentations and everywhere where you do not have space for a big clumsy antenna.

Radiator can be extended a bit with the help of a handy included tool. Comes with several feel of coaxial cable and PL259 connector. Do not forget to buy adapter, if you need another kind of connector.


Omnidirectional magnet-base mobile antenna with cable and coax


Directional log-periodic wideband antenna

Precise manufacturing, excellent technical characteristics and no-tune wideband operation make this log-periodical aerial a recommended aerial for all FM MAX transmitters. Remember that this is a 6-element directional aerial, meaning it radiates most of the power in one direction. This is where amplification comes from.


Directional YAGI wideband antenna


Directional log-periodic wideband antenna

Precise manufacturing, excellent technical characteristics, no-tune wideband operation and extremely high gain (9dBD!!!) make this antenna suitable for receiving faint distant FM signals and for low power FM transmitters, such as PCI MAX. Remember that this is a 7-element directional antenna, meaning it radiates most of the power in one direction. This is where the amplification comes from compared to other antennas.


Directional log-periodic wideband antenna