[R-390] Re: Z503

[Gord Hayward]

Hi Tom,

It should resonate at 455 kHz.  The coil I used looked like one of the 
old loopstick
variable coils for crystal radios.  I think the capacitor was somewhere 
near 30 pF.
I stuck it together and peaked it with a scope and signal generator to 
be sure it
would work before I started the surgery on the 390A.  I removed the can top,
pulled out the old coil and cap, put in the new coil and cap and 
replaced the can
top.  The result looks like it was meant to be there.  Then I repeaked 
it in the
radio as in the standard alignment instructions.

Remember, the Q is quite important.  I did try a smaller coil that also 
peaked,
but the Q was too low so I didn't get enough AGC action.

> <>Hi Gord,
> Could you provide more info about the inductance of the "big honking coil"
> from the junk box? Are you trying to get the coil to resonate at 455 
> khz or
> what?
> Thanks,
> -tom


-- 

Gordon L. Hayward, Ph.D., P.Eng.,
Associate Professor, Biological Engineering,
School of Engineering, University of Guelph,
Guelph, Ontaro, N1G 2W1.