1. Modifiyng TX chain
Dual-circuit 70Mhz band-pass filter. Made on filters 7V1S.
L2 and L3 coils are wound with wire CuAg 0.5 mm. Coupling coils L1 and L3
are wound with isolated Cu wire 0.5mm dia. FTP ethernet cable should be good idea
to get this wire in good isolation.
Filters base should be prepared in advance. This should be done by removing
the legs, cutting any flanges and drilling holes for the coil wires.
First wounding CuAg primary coil, then coupling one as shown below:
After installing in the PCB the filter looks like this ( coupling green wire should
have two turns ):
