I have an insulated radio on a pos ground car with fair reception but
absolutely NO interference or engine hum.  Something else must be the
problem with Stephen's car.
I use Bosch Platinum plugs and Lucas plug wires from Moss, Crane elec.
ignition.
Ulix
On Sun, 14 Jun 1998, Jeff Boatright wrote:
> 
> >My latest problem is due to the addition of a radio. ... Everything works
> >OK but
> >the interference is bad. ...
> >Stephen Oram
> >
> >1966 Sprite MKIII
> 
> 
> Is your car still positive earth? Is the radio a modern one (hence negative
> earth)? If so, then your antenna and radio must be electrically isolated
> from the car body. This means that the antenna has a 'floating' ground.
> Reception will be poor and the effects of interference will be greater.
> There are several remedies:
> 
> 1. Buy an old positive ground radio
> 2. Change the car to negative ground
> 3. Build a circuit for the antenna that compensates for the floating set-up
> (a HAM frined told me how once, I could look it up)
> 
> Each option has it's advantages and disadvantages.
> 
> Jeff Boatright          __o_\__           '65 Austin-Healey Sprite
> http://userwww.service.emory.edu/~jboatri/sprite/sprite.html
> 
> 
    Ulix                                                    __/__,__        
.......................................................... (_o____o_)....
                                                           '67 Sprite
 |