01-06-2012, 09:29 PM
While on the subject of high impedance primary coupling RF coils here is one out of an old comms receiver, there are two coils on the coil former a single layer type and a larger wavewound type.
The single layer coil tunes from 1.6 Mhz to 3 Mhz, although the wave wound coil looks more like LW coil it is in fact the high impedance self resonant primary, the anode connection to this primary has a capacitor of just a few pf going from the anode of the RF amp to the signal end of the secondary (the single layer coil) this coil and its associated tuning capacitor feeds the grid of the mixer. the coils are slug tuned. Note the wave wound coil is shown approx three quaters of its original size...I nicked some of its Litz wire for anothe project....
Lawrence
The single layer coil tunes from 1.6 Mhz to 3 Mhz, although the wave wound coil looks more like LW coil it is in fact the high impedance self resonant primary, the anode connection to this primary has a capacitor of just a few pf going from the anode of the RF amp to the signal end of the secondary (the single layer coil) this coil and its associated tuning capacitor feeds the grid of the mixer. the coils are slug tuned. Note the wave wound coil is shown approx three quaters of its original size...I nicked some of its Litz wire for anothe project....
Lawrence
