This page chronicals the construction and testing of the new 300 watt 1296-MHz amplifier kit being
offered by W6PQL. The amplifier uses four XRF-286 LDMOS transistors removed from Spectrian
2-GHz amplifiers and mounted on new copper pads. More info on these amplifiers found on
W6PQL's website.
Hints: When drilling and tapping holes in the heat sink for the printed circuit boards,
mark two holes on opposite sides and drill and tap them, first. Then using the 4-40 machine
screws provided with the kit secure the board to the heat sink so the remaining hole can be
accurately marked. It is very easy to get holes out of alignment if you mark them all at
one time like Jim tells in his video. Of course you should mark and drill the 6-32 holes for
the power transistors before doing the boards.
When soldering chip components, solder the ground end last as it is easier not having to hold
the chip. Install chip caps and resistors on the pcb, first, then install the variable resistor
by soldering one of the two tabs at one end. This makes line up easier. Tin the solder lands on
the board with a little solder and wick excess off before installing. Be sure to install zener
diodes oriented properly. The curved mark on top of the chip is toward positive voltage. The
other end goes to ground. Use of an ohmeter to figure out which solder land is ground is recommended
to make sure. Removal of a chip component after soldering both ends is tricky and often leads to
breaking the chip, so avoid having to do this be carefully determining in advance where they go.
Placing the shottkey diode and electrolytic capacitors is critical to not short across the narrow
gap between conductors. I found the coils a little ackward and got one oriented backward from
how Jim installed them (shouldn't matter). The tiny 1nF chip cap is tricky to handle. I haven't
soldered the high power termination on the output coupler because I will dc test each board before
soldering the XRF-286's.
I will place photos and updates on the project as it proceeds.
Return to 1296 EME page.