INTRODUCTION
Welcome to the latest innovation in electronics technology using (S)urface (M)ount (T)echnology, or SMT. Just as when the transistor revolutionized the amount of space required to construct electronic circuits, the advent of surface mount components have further “shrunk” the dimensions of what we are accustomed to seeing in modern day circuits. These “chip” components are commonly used in today’s miniature circuits including everything from camcorders to high speed computers. We wanted to design a kit that accentuated their small size, so what better than a micro FM transmitter! Many low cost wireless transmitters are susceptable to frequency drift when held in the hand, placed on a metal table or subject to close proximity of a body. This kit uses crystal control to reduce any possibiliy of frequency drift.
While this kit and manual were designed with the beginner in mind, it should also be stated that this kit qualifies as a “Skill Level 2” due to the nature of the assembly using surface mount components. While this isn’t intended to “scare you off” it is not recommended that this be your first electronics assembly project. While we have included extra SMT components in case you lose or damage a “chip” component, care should still be taken to assemble the kit with the utmost care - an uncontrolled sneeze could blow your kit away!
While the components may seem strange looking at first (where are the leads??!!) rest assured that they are not too difficult to install. A friendly warning, however, don’t pull out your trusty soldering gun for this project (our repair techs have a pet statement, “do you know what the soldering gun’s light is for - it’s to see what you’re burning up!”) as the gun generates too much heat for the tiny solder “tabs” on the component ends. A small pair of tweezers and good eye to hand coordination are also necessary for proper assembly of this kit. A magnifying lens is recommended to check solder connections.
MR6 CIRCUIT DESCRIPTION
The MR6 is a three stage crystal controlled transmitter consisting of a crystal oscillator followed by two frequency multipliers. The crystal oscillator operates at 12, 16 or 24 MHz, depending upon crystal used. The first frequency multiplier is tuned to the fourth, third or second harmonic of the crystal oscillator, producing a stong output at 1/3 of the final 146 MHz output frequency. The second frequency multiplier operates as a frequency tripler, producing the desired 146 MHz output frequency. Broadband coupling is used to allow the user to select different crystals for various output frequencies.
MR6 • 4
