FM Transmitter Help

Jump To			Transmitter Selection Guide
			Transmitter Ranges
			Transmitter Connections
			Transmitter Tuning
			Transmitters and the Law
			Back to Transmitter Product Page

Transmitter Selection Guide

There are a number of factors that you need to consider before purchasing transmitter equipment:

Do you want to broadcast in Stereo or Mono?
Do you want a completely accurate broadcast frequency that will not drift (i.e. PLL tuning)?
What range do you wish to cover (radius in miles or km)?

If money is no object then obviously the more sophisticated you make your set-up the better the results will be. To give you a guide on selecting the products to meet your requirements here are some examples followed by information of power output and transmitting distances you can expect.

If you go down the Modular route in Examples 1 to 4 you can start with the basic configuration in Example 4 and then add extra modules as shown the Examples 1 to 3.

Example 1 - Modular Stereo PLL Transmitter

To build this you will need these three kits:

This set-up can be used to drive one of our high powered Linear FM Amplifier for greater range.

The complete set-up can be used in conjunction with the stereo audio line out from a hi-fi, mixer, soundcard, MP3 player, etc or our kit 1050 - 3 Input Stereo Hi-Fi Preamplifier.

Example 2 - Modular Stereo Transmitter

As example 1 above but omitting the PLL FM Synthesizer (88-108MHz).

To build this you will need these two kits:

This set-up can be used to drive one of our high powered Linear FM Amplifier for greater range.

The complete set-up can be used in conjunction with the stereo audio line out from a hi-fi, mixer, soundcard, MP3 player, etc or our kit 1050 - 3 Input Stereo Hi-Fi Preamplifier.

Example 3 - Modular Mono PLL Transmitter

As example 1 above but omitting the 1079 - FM Stereo Encoder.

To build this you will need these two kits:

This set-up can be used to drive one of our high powered Linear FM Amplifier for greater range.

The complete set-up can be used in conjunction with the audio line out from a hi-fi, mixer, soundcard, MP3 player, etc or our kit 1052 - 3 Input Mono Mixer.

Example 4 - Modular Mono Transmitter

This basic mono setup will give you the ability to upgrade to PLL or Stereo setup at a later date.

1187 - 3 Watt FM VCO Amplifier (88-108MHz)

This transmitter can be used to drive one of our high powered Linear FM Amplifier for greater range.

The complete set-up can be used in conjunction with the audio line out from a hi-fi, mixer, soundcard, MP3 player, etc or our kit 1052 - 3 Input Mono Mixer.

Example 5 - Standalone Mono Transmitter

Any of the transmitters detailed below ccan be used in conjunction with the audio line out from a hi-fi, mixer, soundcard, MP3 player, etc or our kit 1052 - 3 Input Mono Mixer:

Top of Page

Transmitter Ranges

The actual transmitting range of an FM transmitter is determined by a number of factors including the transmitters output power, local terrain, the quality and height of the antenna set-up, interference from other radio stations, the quality of the radio receiver and atmospheric conditions.

Assuming that the antenna has a clear line of sight, the transmitting frequency is clear of other broadcasts and an average quality portable receiver is used, typical transmission power to range figures are as follows:

Watts
ERP
1
2
4
8
15
25

Range
Miles
1.5
2.1
3.0
4.2
5.5
7.0

Top of Page

Transmitter Connections

Most transmitter have just six simple connections that need to be made. You will need a soldering iron (Order Code 4010) and solder (Order Code SOL450) to make the connections to the connection pins provided on the PCB.

AUDIO INPUT - The audio frequency input is connected at points ground and signal. Some kits are supplied with an electret microphone that can be used in place of a line-in audio source if you prefer. Adjust the variable resistor for best audio performance
ANTENNA - The antenna can be a 50 Ohm Open Dipole, Ground Plane, 5/8 or YAGI connected using 50 Ohm coax cable (Order Code RG58)
POWER SUPPLY - connect a power supply with correct voltage that is rated to supply at least the current drawn by the transmitter (see transmitter Technical Specifications). If you already have a power supply of the correct voltage but with a higher current rating then it is also suitable. See our Accessories and Power Supplies pages

The most important thing to remember is that an aerial must ALWAYS be connected to the output before power is applied to the circuit.

Top of Page

Transmitter Tuning

Our transmitters are aligned at factory-set transmitting frequency. This is fine for initial tests but you will soon want to change the frequency to your own setting.

This is really a very simple task that involves turning the screw head in a few variable capacitors. You will need a small flat bladed screwdriver to do this. You will also need an SWR meter (not supplied).

Kits 3028, 3032 and 1028 are supplied with a small peaking circuit that can be used with a simple multimeter (Order Code DMM006) in place of an SWR meter.

Top of Page

Transmitters and the Law

WARNING - It is against the law to transmit a radio signal without an appropriate license or with equipment that is not approved for use in the UK by the Radio Communications Agency (RCA). This transmitter has NOT been approved by the RCA.

Quasar Electronics Limited and it's employees accept no responsibility whatsoever for any consequences arising from the use or misuse of unlicensed or unapproved equipment. If you live outside the UK we suggest that you check local laws before operating or purchasing transmitting equipment. Again, it is your responsibility not to break the law.

Top of Page

FM Transmitter Help