The whole purpose of bypass caps is to return the RF currents to where they
started from. Since it's typical to connect the negative supply to the
chassis and use that as a 'common' point for V+ bypassing, many people think
that bypasses should be connected to chassis 'ground'. In point of fact,
you're really better off bypassing the V+ line (or V-, as the case might
be) directly to the V- line (or V+, as the case might be). This is not a
straightforward matter, and the choice of where's the best place to connect
the bypass is often a complex issue involving the impedance of the return
current path, as well as what other currents from lower level stages might
be sharing that same current path. It's always good to prevent output stage
currents from sharing the same return path as input stage currents. As was
popularized in the movie Ghostbusters, it's not wise to "cross the streams".

Joe
W3JDR


"Bob Liesenfeld" wrote in message
...
Hi gang,
Looking over an old AM/FM radio kit I built some years ago, I notice
that instead of bypass caps going to ground (negative side of 9V), they
all tie into the Vcc line, which has a single bypass cap to ground with
an associated decoupling resistor. Any thoughts on this?

Bob WB0POQ