I found a source who has two of the three 4.5-MHz sound traps that I would need to build this preamp. In the schematic (below) they are L1C1, L2C2, L4C3.
I am wondering about substituting a modern component for coil L3, which is described as:
"North Hills coil no. 120 I set at 400 mu-h"
I see variable inductors at sources like mouser.com, but I'm not sure what (if anything) might work.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
