Which shape?

  • Hello Claudio,

    the left one has the better (not correct) shape. Can be better with a rolloff 0.25, what is usual for DVB-S2.

    The right one is result of a overdriven power amplifier, maybe a Class-C type. On the bottom you can see

    the intermodulation, what happens, when the pa is overdriven and the distance between intermodulation and useful signal is not large enough.

    A DATV PA may only be operated with at least 6 dB less than the possible CW power, the quiescent current must be designed as Class A/B.

    This excample shows the Intermodulation Diagramm.

    Its a 180 Watt CW-PA. You can see, on DATV is only 6dB less (abt. 45 Watt) possible.

    On higher power the IM rises up..... And finaly you can see shoulders of the

    signal over the TP

    This is a shape with rolloff .25 and clas A/B power amplifier. IM distance is on tx side 35dB.

    73 de Robert, DD4YR