"Ross Archer" wrote in message
...

Sounds like a great project! Like anything where there are
unknowns, experimentation is the fun way to go, so don't
hesitate to try different things.

The second, smaller ferrite to couple the signal into your
receiver is presumably in parallel with the 8" loopstick.
It's just that a bunch of coaxial cable is in-between.
Inductors in parallel have less inductance than either of
the two inductors, so this will throw you off using
equations built to serve the case of one loopstick and one
variable capacitor. This might cause you to need more
capacitance, which fortunately is easy to do by adding a
series of small caps in parallel until you achieve the
desired tuning range.

Someone else mentioned the extra capacitance added by the
coax. I'd *think* (I may well be all wet) that this extra
capacitance is a good thing given the partial loss in
inductance.


The extra capacitance will cause a problem with the tuning range by
reducing the difference in the capacitance ratio of the tuning
capacitor. A 10 to 360 pf tuning cap will tune about a 4 to 1 ratio
with a normal fixed inductance with a typical amount of distributed
capacitance. Putting another 100 pf or more of capacitance in parallel
would reduce the tuning range to less than 3 to 1, which is less than
range of the AM broadcast band. Anyway, that's my instinct on this one.
There's a square law relationship between the tuning ratio and the
capacitance ratio but I really don't want to run the numbers.

I suggested using a link of a few turns to connect the coax rather than
putting the coax directly across the tuning cap in order to reduce the
added capacitance. That sort of hookup would probably also reduce the
energy transfer, but that gets into all that Nikola Tesla stuff, and I
really, really don't want to run those numbers.

Frank Dresser