|The first step in integrating the amplifier
to the xcam2 transmitter was to examine the topology of the transmitter.
The layout of the circuit board is actually very conducive to the addition
of this particular amplifier. This picture shows the circuit board
with an overlay of how the amplifier module will be placed.
|One problem I saw with the amplifier module
was that it didn't actually have pins. Instead, it was in a modified
surface mount package, with the contacts on small pads on the underside
of the unit. To make all the connections, I adopted a "house on stilts"
approach. All the ground connections would be made by resting the
unit on very short lengths of solid 14 gauge copper wire. The remaining
pads on the amplifier would then be suspended about 2mm above the circuit
board, thereby allowing me to make my connections without shorting the
pads to ground. Note that the RF in was also put on a "stilt", but
instead of being connected to ground, it rested on the RF out from the
transmitter circuit board. Note the current limiting resistor which
connects Vcc to +12 on the transmitter board
|This picture shows the other side of the
amp module. For simplicity the "stilts" under the 3 pads on the left
is actually a short length of 14 guage solid copper wire soldered to the
transmitter board. I had to scrape off the protective coding from
the circuit board to make a connection to ground. The amp module
was then laid on top of the wire, and a soldering iron was touched briefly
at each pad to fuse it to the wire. The antenna wire is soldered
to the right most pad. For ease of installation, I soldered the signal
wire to the amp module BEFORE resting the amp module on the 14 guage "stilts".
A bit of of the protective coding was scraped from the transmitter board
and the coax shielding soldered down.
|And here we have an overall perspective
of the modification. The resistor taps into power right where power
comes into the transmitter board. Note that the amp module is tall
enough to prevent the transmitter from being placed back in the case, unless
the case is modified by cutting a hole over the amp module. Also
note that I used a 1/2 watt resistor, which might be too little, as the
resistor gets very warm, but not hot.