[ARC5] BC-453 mods

[Ian Wilson]

Just to return to the original thread for a moment, the poster
was describing a set that had already been comprehensively
modified, and was looking for a way to restore the BFO
function in a small amount of available space.

So I don't think this thread is in any danger of causing working
RX to be modified to use solid state devices. On the other hand,
revitalizing unused OS-8 scopes seems like a really good thing
to do no matter how invasive :).

Just a quick note on compounds:
  - a Darlington generally has the emitter of the first stage directly
    coupled to the base of the second stage: the effective beta is
    then the product of the individual betas
  - a cascode has a common-emitter (or source) input stage with
    a common base (or gate) second stage. If the same type (NPN
    or PNP) then they connect in series and can be used to handle
    high voltages with decent gain-bandwidth. If they are
    complementary types (solid state only, of course) then this is
    a 'folded' cascode

73, ian K3IMW