[SignalOne] Q2 Warm?

[John Seboldt]

At 02:18 PM 1/6/03 -0500, you wrote:
>Another probably dumb question. Should Q2 (2N3866) on the driver board
>run quite warm, even in standby? Mine gets quite warm, just in PTT
>without keying anything.

No immediate answer... but just a note that I was curious from the start 
why they didn't key the bias on the whole driver stage, like many modern 
solid-state rigs I know.  The constant heating, conducted to the chassis, 
is surely a major cause of drift to the nearby PTO's unless the temperature 
compensation is really right on. On the contrary, such humble rigs as the 
Ten Tec Argosy will key the bias with each keying element, and this has 
been my example to follow in my homebrew efforts.

In fact, the whole biasing scheme is pretty primitive, being all 
resistor-based. When I got my basket-case CX7A, there was hardly any 
current flowing in the drivers. No wonder my first SSB contact had such bad 
reports - I was probably splattering all over the band from having a Class 
C or B driver! A little advice from Mark Mandelkern on how much current was 
supposed to be flowing, and linearity returned (as well as the heat...)

John K0JD
Milwaukee