CONVERSION 70cm DJ9BV PreAmp to ATF54143



 A lot of folks use the DJ9BV preamps for 70cm, as they were sold as
kits by DC3XY...and have a solid mechanical construction. The preamp
uses a MGF1302, which is no up to date transistor anymore. So the idea
came up to use the nice mechanics and switch the transistor. The input
is narrowband because the preamp is intended for tropo with less attention
to the noise figure (which is excellent anyway). For the artwork I used
the "we take a knife and cut little islands on the pcb"-method.
Points [1] and [2] are  for marked for bias insertation. For Values (passive
biasing is sufficent) and further referenence have a look at: OZ2OE HP.

Circuit:

schematics

L2=L3 diameter: 0.6mm CU

                     
Fig. a look at the stripline                                                 Fig. preamp with 3 pole helix + 10dB attenuator

Plot


Fig. Plot between 100-1000MHz...F=0.5dB (tnx DL4DTU)