Who reconized this RF Power Amplifier?

[Albert H]

Marcel is exactly right. There are two problems with having the inductors close to the board - the groundplane beneath the coil will "damp" it, reducing its "Q", and there will be capacitive coupling between the coil and the groundplane.

The problems can be overcome in several ways - don't have groundplane beneath the coils, change the orientation of the coils ( Elonos filters I have seen use vertical coils), or etch the coils into the PCB!

At UHF I frequently use etched lines ("Lecher Bars") for tuned circuits. At those frequencies, the dimensions of the "coils" are pretty small. At VHF, the coils are bigger, but still manageable.

Years ago I designed a PCB for a BGY33 power output module, that used etched output filter coils. It was only good for about 25 Watts at the absolute maximum (the BGY33 module was rated at 20 Watts), but the output was completely clean. I designed a little 150mW PLL exciter to drive the BGY33 or BGY133, and it made for a completely "no-tune" 25 Watt rig - rocket science back in 1979! I recently found a small cache of BGY33 modules, and built a few of the little rigs for RSL (or similar) use.