Hi

On Sun, 24 Oct 2004 14:30:59 -0700, The Eternal Squire
wrote:

Hi,

I've been trying to build my first superhet but I have been having problems.

snip details


However, when I try to use capacitive or inductive coupling between
the stages, I get the classic symptoms of motorboating... 10 to 45 hz
out of the loudspeaker.

I have the ground planes of each respective board on a piece of aluminum
foil, and both boards are connected in parallel to the 9V battery.

Advice, anyone?

Thanks,

The Eternal Squire


Some wild guesses g

- not enough decoupling on the 9v rail of the audio power amp (a
couple of hundred uF's as close as possible to the chip)

- speaker leads running too close to the inputs to the x100 amp

- try running the x100 board at less than 9v (anything from some
resistance and a decent electrolytic in the 9v line up to some
'proper' voltage regulation)

- some kind of an earth loop ? - if the board are connected by coax
try lifting the braid at one end of the cable

Hope these help ....?

Adrian
Suffolk UK