Instruction manual

FMLP1 • 4
INTRODUCTION
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.
Enough already… what are we about to build?
The FM Low Pass Filter kit came about while designing the circuitry for
the PX1, Professional FM Broadcaster. The PX1 is a 35 Watt professional
grade FM stereo broadcast transmitter developed to meet the criteria of the
FCC Ruling 99-25. This ruling created a class of radio stations designed to
serve localized communities by authorizing new classes of noncommercial low
power FM radio services (LPFM). In order to meet the stringent guidelines of
the FCC, the PX1 underwent months of design sessions and many hours of
painstaking tests. One of the secrets to its clean output is the design
implementation of the FMLP1.
The FMLP1 offers the user superb Input Return Loss for the FM
Broadcast band, typically –18 dB or better. The filter’s Insertion Loss averages
about –60 dB up in the 2
nd
harmonic range of 176 MHz to 216 MHz eliminating
any unwanted signals.
The issue concerning harmonic frequency components for the FM
Broadcast band, especially the 2
nd
harmonics (176 - 216 MHz), is the possibility
of interference problems in other areas like the VHF TV High Band. This is not
a good thing and is frowned upon by the FCC!
The FMLP1 design was developed specifically to make our PX1
comply with the FCC guidelines. After its completion we thought to ourselves…
Hey I bet our customers would like this for their applications! Thus the kit
version of the FMLP1 was born.