Hi, operating the ebay's
Rockmite 40m CW kit (7023kHz) with a D882 final PA transistor.
In past I did some experiments with replacing it with a BD139-16 (ST), resulting in half of the output power (measured the amplitude of the signal with an oscope on a dummy load).
I got ~6W with 882, about ~3W with BD139.
Today I've smoked the 882 final finally
and I've replaced it with the BD139 again.
While reading the datasheets I can see the D882 has got around half of max voltages and twice the max currents against the BD139.
Also the DS of the 882 shows Ft=100MHz, while BD139's DS does not show any Ft at all.
Still investigating how to get the BD139 working in that circuit with a similar output power.
Any hint on it?
PS: my pcb version has got a protection zener (1n4755 in series with 1n4148) at transformer's output (it seems to me the protection should be at the 882's collector, imho). The newer pcb lacks the protection (from the photo there is none zener).